DIN V 18599-2 Energy efficiency of buildings — Calculation ...tc76.org/spc100/docs/IBP...

Date: 2007 February

DIN V 18599-2

Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 2: Energy needs for heating and cooling of building zones

Energetische Bewertung von Gebäuden — Berechnung des Nutz-, End- und Primärenergiebedarfs für Heizung, Kühlung, Lüftung, Trinkwarmwasser und Beleuchtung — Teil 2: Nutzenergiebedarf für Heizen und Kühlen von Gebäudezonen

Supersedes DIN V 18599-2:2005-07

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Contents Page

Foreword..............................................................................................................................................................6 Introduction .........................................................................................................................................................8 1 Scope ......................................................................................................................................................9 2 Normative references ......................................................................................................................... 10 3 Terms and definitions, symbols and units....................................................................................... 12 3.1 Terms and definitions ........................................................................................................................ 12 3.2 Symbols, units and subscripts.......................................................................................................... 13 4 Relationship between the parts of the DIN V 18599 series of prestandards ................................ 17 4.1 Input parameters from other parts of the DIN V 18599 series of prestandards ........................... 17 4.2 Output parameters for other parts of the DIN V 18599 series of prestandards ........................... 19 4.3 Determination of the energy use for various types of technical building systems

according to the DIN V 18599 series of prestandards .................................................................... 20 5 Monthly balance calculation method................................................................................................ 21 5.1 Principle of balance calculation method.......................................................................................... 21 5.1.1 Balance boundaries and calculation period .................................................................................... 21 5.1.2 Heat sources and heat sinks ............................................................................................................. 21 5.1.3 Utilization of heat sources and heat sinks....................................................................................... 22 5.1.4 Factors affecting the heat sources and heat sinks......................................................................... 22 5.2 Balance equations for calculating the energy needs of a building zone for heating and

cooling ................................................................................................................................................. 23 5.2.1 General................................................................................................................................................. 23 5.2.2 Balance equations for calculating the energy need for heating.................................................... 23 5.2.3 Balance equations for calculating the energy need for cooling.................................................... 24 5.2.4 Accounting for weekend and holiday-period operation ................................................................. 24 5.2.4.1 Balance of the energy need for heating ........................................................................................... 24 5.2.4.2 Balance of the energy need for cooling ........................................................................................... 25 5.2.5 Monthly values and annual values.................................................................................................... 25 5.3 Heat sinks ............................................................................................................................................ 27 5.3.1 General................................................................................................................................................. 27 5.3.2 Transmission heat sinks.................................................................................................................... 27 5.3.3 Ventilation heat sinks......................................................................................................................... 28 5.3.4 Internal heat sinks .............................................................................................................................. 29 5.3.5 Heat sinks due to radiative heat transfer ......................................................................................... 30 5.3.6 Heat storage ........................................................................................................................................ 30 5.4 Heat sources ....................................................................................................................................... 30 5.4.1 General................................................................................................................................................. 30 5.4.2 Heat sources due to solar radiation.................................................................................................. 31 5.4.3 Transmission heat sources ............................................................................................................... 32 5.4.4 Ventilation heat sources .................................................................................................................... 33 5.4.5 Internal heat sources.......................................................................................................................... 34 5.5 Utilization of the heat sources........................................................................................................... 35 5.5.1 General................................................................................................................................................. 35 5.5.2 (Thermal) time constant of the building zone.................................................................................. 36 5.5.3 Utilization factor.................................................................................................................................. 36 6 Determination of individual parameters for the monthly balance ................................................. 36 6.1 Room temperature assumptions....................................................................................................... 36 6.1.1 Reference internal temperature for calculating the energy need for heating .............................. 38 6.1.1.1 Reduced heating at night................................................................................................................... 38 6.1.1.2 Reduced heating operation during weekends and holiday periods.............................................. 39

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6.1.1.3 Partial heating (spatially reduced heating operation) .....................................................................40 6.1.1.4 Combination of partial heating and reduced heating ......................................................................41 6.1.2 Reference internal temperature for cooling......................................................................................41 6.1.3 Temperature of an adjacent unheated or uncooled zone ...............................................................41 6.1.3.1 General .................................................................................................................................................41 6.1.3.2 Approximate method using temperature correction factors to determine the mean

temperatures in unheated zones .......................................................................................................42 6.1.3.3 Detailed calculation of the temperature in an unheated or uncooled building zone ...................44 6.1.4 Temperature of an adjacent heated or cooled zone ........................................................................45 6.2 Transmission heat sinks/heat sources .............................................................................................46 6.2.1 Direct transmission to the external environment ............................................................................46 6.2.1.1 Calculation of the heat sinks and sources due to transmission to the external

environment .........................................................................................................................................46 6.2.1.2 Calculation of coefficients of heat transfer to the external environment (assuming a

standard allowance for thermal bridges) ..........................................................................................46 6.2.1.3 Calculation of coefficients of heat transfer to the external environment (using linear

thermal transmittance)........................................................................................................................47 6.2.2 Transmission through unheated or uncooled spaces to the external environment....................47 6.2.3 Transmission to adjacent heated or cooled building zones...........................................................49 6.2.4 Transmission through the ground.....................................................................................................50 6.3 Ventilation heat sinks/sources...........................................................................................................50 6.3.1 Infiltration .............................................................................................................................................50 6.3.1.1 Determination of the infiltration air change rate ..............................................................................51 6.3.1.2 Evaluation of infiltration of zones with mechanical ventilation systems......................................52 6.3.2 Window airing ......................................................................................................................................53 6.3.2.1 Determination of air change rate due to window airing ..................................................................54 6.3.2.2 Usage-dependent minimum air exchange with external air............................................................57 6.3.3 Mechanical ventilation ........................................................................................................................57 6.3.3.1 Determination of the mean air change rate due to ventilation systems........................................58 6.3.3.2 Air change due to supply air from mechanical ventilation systems..............................................59 6.3.3.3 Extract air change due to mechanical ventilation systems ............................................................60 6.3.3.4 Supply air temperature of mechanical ventilation ...........................................................................60 6.3.3.5 Note on the evaluation of ventilation systems with extract air/supply air heat exchangers

for use in residential buildings ..........................................................................................................61 6.3.4 Ventilation in unheated or uncooled building zones.......................................................................61 6.3.5 Air exchange between building zones ..............................................................................................62 6.3.5.1 Supply air change rate from adjacent building zones.....................................................................63 6.3.5.2 Extract air change rate into adjacent zones .....................................................................................64 6.4 Radiation heat sources and sinks .....................................................................................................65 6.4.1 Heat sources due to solar radiation entering through transparent surfaces ...............................65 6.4.2 Solar heat gains via opaque building elements ...............................................................................69 6.4.3 Solar heat gains via unheated or uncooled sunspaces (glazed annexes) ....................................71 6.4.3.1 Direct solar heat gains in the building zone.....................................................................................72 6.4.3.2 Heat gains affecting the unheated or uncooled sunspace (glazed annex) ...................................73 6.4.3.3 Calculation of balances for glass double façades...........................................................................74 6.5 Internal heat sources and sources of cold .......................................................................................74 6.5.1 Internal heat sources in residential buildings..................................................................................74

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6.5.2 Heat sources due to persons ............................................................................................................ 74 6.5.3 Heat sources and sinks due to machinery and equipment............................................................ 75 6.5.4 Internal heat sources/heat sinks due to movement of materials................................................... 75 6.5.5 Heat sources due to artificial lighting............................................................................................... 76 6.5.6 Heat sources and sinks due to heating, cooling, domestic hot water supply and

ventilation systems............................................................................................................................. 77 6.6 Taking into account stored heat between days of usage and non-usage.................................... 78 6.7 Utilization factors of heat sources.................................................................................................... 79 6.7.1 Effective heat capacity (thermal mass) ............................................................................................ 79 6.7.2 (Thermal) time constant ..................................................................................................................... 80 6.7.3 Utilization factor.................................................................................................................................. 81 6.7.4 Limits for the utilization factor .......................................................................................................... 82 Annex A (normative) Shading factors and movable solar protection devices.......................................... 83 A.1 General................................................................................................................................................. 83 A.2 Correction factors for external shading ........................................................................................... 83 A.3 Evaluation of movable solar protection devices ............................................................................. 90 Annex B (normative) Maximum heating power in the building zone.......................................................... 91 B.1 General................................................................................................................................................. 91 B.2 Calculation of the maximum heating power Q

⋅h,max for a design reference day (without

mechanical ventilation) ...................................................................................................................... 91 B.3 Design conditions............................................................................................................................... 92 B.4 Maximum heating power, taking into consideration a mechanical ventilation system .............. 92 Annex C (normative) Maximum cooling power in the building zone.......................................................... 95 C.1 General................................................................................................................................................. 95 C.2 Calculation of the required maximum cooling power..................................................................... 95 C.3 Design conditions............................................................................................................................... 96 C.4 Calculation of heat sources and sinks under design conditions .................................................. 97 C.4.1 Heat transmission to the external environment .............................................................................. 98 C.4.2 Heat transmission through the ground ............................................................................................ 98 C.4.3 Other transmission heat flows .......................................................................................................... 99 C.4.4 Heat flows due to infiltration ............................................................................................................. 99 C.4.5 Heat flows due to window airing....................................................................................................... 99 C.4.6 Heat flows due to supply air from a mechanical ventilation system........................................... 100 C.4.7 Heat flows due to air entering from adjacent zones ..................................................................... 100 C.4.8 Solar heat gains via transparent building elements ..................................................................... 100 C.4.9 Solar heat gains via opaque elements ........................................................................................... 100 C.4.10 Solar heat gains via building elements with transparent thermal insulation............................. 101 C.4.11 Solar heat gains via unheated sunspaces (glazed annexes) ....................................................... 102 C.4.12 Internal heat sources and heat sinks.............................................................................................. 102 C.5 Cooling power required in a building zone equipped with a mechanical ventilation system .. 103 Annex D (normative) Calculation of monthly heating and cooling times ................................................ 105 D.1 General............................................................................................................................................... 105 D.2 Monthly heating time........................................................................................................................ 105 D.3 Monthly cooling time........................................................................................................................ 106 Annex E (informative) Default values of volume flow of HVAC systems ................................................. 108 E.1 General............................................................................................................................................... 108 E.2 Default values for the permissible volume flow ............................................................................ 108 Bibliography................................................................................................................................................... 110

Figures

Figure 1 — Overview of the parts of DIN V 18599 .............................................................................................. 8 Figure 2 — Content and scope of DIN V 18599-2 (schematic diagram) ........................................................... 10

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Figure 3 — Determination of the energy needs of a building zone for heating and cooling ..............................22 Figure 4 — Diagram representing the thermal quantities to be taken into consideration for sunspaces

(glazed annexes).........................................................................................................................................72 Figure 5 — Examples of two types of air-handling luminaire .............................................................................76 Figure A.1 —Horizon angle ................................................................................................................................83 Figure A.2 — Overhang angle............................................................................................................................85 Figure A.3 — Lateral shading angle (fin angle)..................................................................................................88 Figure E.1 — Relationship between the maximum cooling power and the permitted volume flow as a

function of the type of air conditioning system ..........................................................................................109

Tables

Table 1 — Symbols and units.............................................................................................................................13 Table 2 — Subscripts .........................................................................................................................................15 Table 3 — Temperature correction factors for various building elements .........................................................43 Table 4 — n50 design values (default values for untested buildings) ................................................................52

Table 5 — Default values for characteristics of glazing and solar protection devices a ....................................68 Table 6 — Default values for solar radiation absorption coefficients of various surfaces for the energy-

relevant part of the solar radiation spectrum...............................................................................................70 Table 7 — Default values for lighting heat gain coefficients µL for air-handling luminaires...............................77

Table A.1 — Partial shading correction factors Fh for various horizon angles and surface surface angles......84

Table A.2 — Partial shading correction factors Fo for horizontal overhangs and various surface angles.........86

Table A.3 — Partial shading correction factors Ff for lateral shading................................................................88

Table A.4 — Parameter a for evaluating the effect of the activation of manually operated or timer-operated solar protection devices for various surface angles.....................................................................90

Table A.5 — Parameter a for evaluating the effect of activation of solar protection devices operated automatically in relation to the solar irradiance, for various surface angles ...............................................90

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Foreword

This prestandard has been prepared by DIN Joint Committee NA 005-56-20 GA Energetische Bewertung von Gebäuden of the Normenausschuss Bauwesen (Building and Civil Engineering Standards Committee), which also lead-managed the work, and Normenausschuss Heiz- und Raumlufttechnik (Heating and Ventilation Standards Committee) with the co-operation of the Normenausschuss Lichttechnik (Lighting Technology Standards Committee).

A prestandard is a standard which cannot be given full status, either because certain reservations still exist as to its content, or because the manner of its preparation deviates in some way from the normal procedure.

No draft of the present prestandard has been published.

Comments on experience with this prestandard should be sent:

⎯ preferably by e-mail containing a table of the data, to [email protected]. A template for this table is provided on the Internet under the URL http://www.din.de/stellungnahme;

⎯ or as hard-copy to Normenausschuss Bauwesen (NABau) im DIN Deutsches Institut für Normung e. V., 10772 Berlin, Germany (office address: Burggrafenstrasse 6, 10787 Berlin, Germany).

The DIN V 18599 series of prestandards Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting consists of the following parts:

⎯ Part 1: General balancing procedures, terms and definitions, zoning and evaluation of energy carriers

⎯ Part 2: Energy needs for heating and cooling of building zones

⎯ Part 3: Energy need for air conditioning

⎯ Part 4: Energy need and delivered energy for lighting

⎯ Part 5: Delivered energy for heating systems

⎯ Part 6: Delivered energy for ventilation systems and air heating systems for residential buildings

⎯ Part 7: Delivered energy for air handling and air conditioning systems for non-residential buildings

⎯ Part 8: Energy need and delivered energy for domestic hot-water systems

⎯ Part 9: Delivered and primary energy for combined heat and power plants

⎯ Part 10: Boundary conditions of use, climatic data

The DIN V 18599 series of prestandards provides a methodology for assessing the overall energy efficiency of buildings. The calculations enable all energy quantities required for the purpose of heating, domestic hot water heating, ventilation, air conditioning and lighting of buildings to be assessed.

In the described procedures, the DIN V 18599 series of prestandards also takes into account the interactive effects of energy flows and points out the related consequences for planning work. In addition to the calculation procedures, the use- and operation-related boundary conditions for an unbiased assessment (i.e.

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independent of the behaviour of individual users and of the local climatic data) to determine the energy needs are specified.

The DIN V 18599 series of prestandards is suitable for determining the long-term energy needs of buildings or parts of buildings as well as for assessing the possible use of renewable sources of energy in buildings. The procedure is designed both for buildings yet to be constructed and for existing buildings, and for retrofit measures for existing buildings.

Amendments

This prestandard differs from DIN V 18599-2:2005-07 in that it has been revised in form and content.

Previous editions

DIN V 18599-2: 2005-07

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Introduction

When an energy balance is calculated in accordance with the DIN V 18599 series of prestandards, an integrative approach is taken, i.e. the building, the use of the building, and the building’s technical installations and equipment are assessed together, taking the interaction of these factors into consideration. In order to provide a clearer structure, the DIN V 18599 series of prestandards is divided into several parts, each having a particular focus. Figure 1 provides an overview of the topics dealt with in the individual parts of the series.

Figure 1 — Overview of the parts of DIN V 18599

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1 Scope

The DIN V 18599 series of prestandards provides a methodology for calculating the overall energy balance of buildings. The described algorithm is applicable to the calculation of energy balances for:

⎯ residential buildings and non-residential buildings;

⎯ planned or new building construction and existing buildings.

The procedure for calculating the balances is suitable for:

⎯ balancing the energy use of buildings with partially pre-determined boundary conditions;

⎯ balancing the energy use of buildings with freely-selectable boundary conditions from the general engineering aspect, e.g. with the objective of achieving a good comparison between calculated and measured energy ratings.

The balance calculations take into account the energy use for:

⎯ heating,

⎯ ventilation,

⎯ air conditioning (including cooling and humidification),

⎯ heating the domestic hot water supply, and

⎯ lighting

of buildings, including the additional electrical power input (auxiliary energy) which is directly related to the energy supply.

This document specifies methods of calculating the energy needs for heating and cooling of the section of the building being assessed. The calculations are based on a specific zone of the building defined according to its intended use. The method of defining building zones is described in DIN V 18599-1. DIN V 18599-10 specifies boundary conditions with respect to room temperature, internal loads, lighting and air change requirements relating to the different type of room usage.

The procedures described in this standard are suitable for calculating the energy need for heating of building zones which have only heating, as well as the energy needs for heating and cooling of building zones which are served by both heating and cooling systems. Particular attention is paid to determining the energy needs for heating and cooling of building zones equipped with ventilation and air conditioning systems. Methods to determine the total energy needs for heating and cooling of buildings with ventilation and air conditioning systems are described in DIN V 18599-3, which specifies the heat, cooling energy, steam and electrical energy required for operating fans for air conditioning and transport.

To calculate the energy needs for heating and cooling, all heat sources and sinks within the building zone shall be determined and included in the balance calculations. These calculations shall also include the results of other calculations described in other parts of the DIN V 18599 series of prestandards (e.g. energy gains due to artificial lighting as described in DIN V 18599-4, uncontrolled heat gains due to the heating system as described in DIN V 18599-5, etc.).

Energy needs for heating and cooling are the result of interaction between the technical characteristics of the building and the building’s technical installations and equipment and of the requirements arising from the type of usage. Potential energy savings which may be achieved by modifications to the building can be estimated by determining the energy needs for heating and cooling.

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The energy needed for heating and, where applicable, for cooling the building zone shall be provided by heating and cooling systems. The energy used by the heating and cooling systems for supplying energy to the zone being evaluated is determined in DIN V 18599-5 to DIN V 18599-9. The values of energy need calculated according to this document are the basis for calculating the energy use of the heating and cooling systems.

This method is not suitable for calculating the energy needs for heating or cooling of building zones with double glass facades. As long as no generally approved method of calculating energy characteristics of double glass facades is known, all façades of this type which are subdivided into individual storeys can be included in the calculations by being treated as sunspaces (unheated glazed annexes).

Figure 2 shows the scope of this document as a diagram. For the reader’s orientation, all other parts of the DIN V 18599 series of prestandards contain an illustration similar to Figure 2 as shown here, and in which the respective energy components dealt with are shown in colour.

Figure 2 — Content and scope of DIN V 18599-2 (schematic diagram)

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

DIN V 18599-1, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 1: General balancing procedures, terms and definitions, zoning and evaluation of energy carriers

DIN V 18599-3, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 3: Energy need for air conditioning

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DIN V 18599-4, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 4: Energy need and delivered energy for lighting

DIN V 18599-5, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 5: Delivered energy for heating systems

DIN V 18599-6, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 6: Delivered energy for ventilation systems and air heating systems for residential buildings

DIN V 18599-7, Energy efficiency of buildings — Calculation of the energy needs needs, delivered energy primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 7: Delivered energy for air handling and air conditioning systems for non-residential buildings

DIN V 18599-8, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 8: Energy need and delivered energy for domestic hot water systems

DIN V 18599-9, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 9: Delivered and primary energy for combined heat and power plants

DIN V 18599-10, Energy efficiency of buildings — Calculation of the energy needs, delivered energy and primary energy for heating, cooling, ventilation, domestic hot water and lighting — Part 10: Boundary conditions of use, climatic data

DIN 4108-2, Thermal insulation and energy economy in buildings — Part 2: Thermal protection and energy economy in buildings – Part 2: Minimum requirements for thermal insulation

DIN V 4108-4, Thermal insulation and energy economy in buildings — Part 4: Hygrothermal design values

DIN 4108-7, Thermal insulation and energy economy of buildings — Part 7: Airtightness of building, requirements, recommendations and examples for planning and performance

DIN EN 832, Thermal performance of buildings — Calculation of energy use for heating — Residential buildings

E DIN EN ISO 6946, Building components and building elements — Thermal resistance and thermal transmittance — Calculation method

DIN EN ISO 7345, Thermal insulation — Physical quantities and definitions

DIN EN ISO 9288, Thermal insulation — Heat transfer by radiation — Physical quantities and definitions

DIN EN ISO 10077-1, Thermal performance of windows, doors and shutters — Calculation of thermal transmittance — Part 1: General

DIN EN ISO 10211-1, Thermal bridges in building construction — Heat flows and surface temperatures — Part 1: General calculation methods

DIN EN ISO 10211-2, Thermal bridges in building construction — Calculation of heat flows and surface temperatures — Part 2: Linear thermal bridges

DIN EN 13363-1, Solar protection devices combined with glazing — Calculation of solar and light transmittance — Part 1: Simplified method

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DIN EN 13363-2, Solar protection devices combined with glazing — Calculation of solar and light transmittance — Part 2: Detailed calculation method

DIN EN ISO 13370:1998-12, Thermal performance of buildings — Heat transfer via the ground — Calculation methods

E DIN EN ISO 13786 Thermal performance of building components — Dynamic thermal characteristics — Calculation methods

DIN EN ISO 13789, Thermal performance of buildings –Transmission heat loss coefficient — Calculation method

DIN EN ISO 13790, Thermal performance of buildings — Calculation of energy use for space heating

DIN EN 13947, Thermal performance of curtain walling — Calculation of thermal transmittance

3 Terms and definitions, symbols and units

For the purposes of this document, the terms and definitions given in DIN EN 832, DIN EN ISO 6946, DIN EN ISO 7345 and DIN EN ISO 9288 and the following terms, definitions, symbols, units and subscripts apply.

3.1 Terms and definitions

3.1.1 effective heat capacity (thermal mass) that part of the heat capacity of a building zone which has an effect on the energy need for heating and on room conditioning in summer

3.1.2 transmission heat transfer coefficient heat flow through an element per unit of time, in relation to the difference between the air temperatures on either side of the element (this being equal to the reciprocal value of the overall thermal resistance of the element)

3.1.3 ventilation heat transfer coefficient heat exchange by an air flow per unit of time, in relation to the temperature difference (heating power of an air flow, in relation to the temperature difference)

3.1.4 product data manufacturer-specific data on the basis of

⎯ a declaration of conformity to harmonized European specifications or corresponding European directives, or

⎯ a declaration of conformity to generally recognized technical standards, or

⎯ a building-inspectorate certificate of usability

that is suitable for this calculation procedure

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3.1.5 default value data which can be used for the calculation if no suitable product data are available for the calculation procedure

3.2 Symbols, units and subscripts

Table 1 — Symbols and units

Symbol Meaning Common unit

A Area m²

a Numerical parameter —

AB Reference area m2

c Specific heat capacity kJ/(kg · K), Wh/(kg · K)

Cwirk Effective heat capacity of a building zone kJ/K, (W · h)/K

dmth Number of days in the month d/mth

dnutz (Mean) number of usage days in the month d/mth

dwe (Mean) number of days with weekend or holiday period operation in the month d/mth

ewind Wind shielding coefficient —

fNA Correction factor to account for reduced heating operation at night time

ftb Correction factor to account for reduced heating operation in certain spaces

fV,mech Factor for evaluating infiltration in the case of mechanical ventilation —

fwind Wind shielding coefficient —

fwe Correction factor to account for reduced heating operation over several days

F Factor —

Ff Radiation-effective form factor between element and sky, or partial shading correction factor for fins —

FF Frame factor —

FS Shading coefficient —

Fu Temperature correction factor for elements adjacent to unheated spaces —

FV Dirt depreciation factor —

Fw Correction factor to account for oblique incidence of solar radiation —

Fx Temperature correction factor for element type x —

geff Effective total energy transmittance —

gtot Total energy transmittance taking into account solar protection devices —

g⊥ Total energy transmittance for perpendicular incidence of solar radiation —

hr External radiative heat transfer coefficient W/(m2 · K)

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Table 1 (continued)


H Heat transfer coefficient, general W/K

HT Transmission heat transfer coefficient for the entire building zone W/K

HT,D Heat transfer coefficient for transmission between the heated building zone and external air W/K

HT,s Heat transfer coefficient for transmission through the ground W/K

HV Ventilation heat transfer coefficient W/K

HV,inf Infiltration heat transfer coefficient W/K

HV,win Heat transfer coefficient for window airing W/K

HV,mech Heat transfer coefficient for mechanical ventilation W/K

HV,mech,ϑ Temperature-weighted heat transfer coefficient for mechanical ventilation W/K

Is Mean monthly solar irradiance W/m2

l Length (of a linear thermal bridge) m

n Air change rate according to DIN EN ISO 7345 h–1

n50 Air change rate at a pressure difference of 50 Pa h–1

Wh, kWh Q Heat, quantity of heat according to DIN EN ISO 7345

Wh/a, kWh/a

Q& Mean heating power W, kW

Qsink Heat sinks Wh, kWh

Qsource Heat sources Wh, kWh

QS Solar heat gains, radiation heat Wh, kWh

QI Internal thermal gains (heat or cold) Wh, kWh

Qh,b Balanced energy need for heating of the building zone Wh, kWh

Qc,b Balanced energy need for cooling of the building zone Wh, kWh

QS,tr Solar heat gains from transparent surfaces Wh

QS,op Solar heat gains/losses by/from opaque surfaces Wh

R Thermal resistance, surface resistance (m2 · K)/W

t Time, time period h

tV,mech Daily operating time of the mechanical ventilation system h

U Thermal transmittance W/(m2 · K)

V Net volume of the space (ventilated volume) m3

V⋅ Volume flow m3/s, m3/h

α Absorption coefficient for solar radiation (opaque surfaces) —

αsp Solar radiation absorption coefficient of the partition between the unheated sunspace and the core building —

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Table 1 (continued)


ϑe External air temperature °C

ϑi Reference internal temperature °C

ϑi,c,soll Internal set-point temperature for cooling during periods of use (“usage periods”) °C

ϑi,h,soll Internal set-point temperature for cooling during usage periods °C

ϑV,mech Supply air temperature of a mechanical ventilation system °C

ϑu Air temperature in an unheated or uncooled zone °C

ϑz Reference internal temperature of an adjacent heated or cooled zone

Δϑer Difference between the external air temperature and sky temperature K

λ Thermal conductivity W/(m · K)

η Utilization factor —

ηV,mech Overall performance factor for efficiency of heat recovery by the supply air/extract air heat exchanger —

γ Ratio of heat sources to heat sinks —

Ψ Linear thermal transmittance (also: thermal bridge loss coefficient) W/(m · K)

Φ Heat flow W

τ (Thermal) time constant (of a building zone) h

τe Radiation transmittance —

ρe Radiation reflectance —

ρ Density; bulk density kg/m3

Table 2 — Subscripts

Index Meaning

a Year (annum), e.g. 1/a = annual

a Air

ABL Extract air (of a mechanical ventilation system)

b Net energy (as in “energy need”)

B Solar protection device (e.g. blind)

c Cooling

C Relating to heat storage

e External, or from a specified layer outwards to the ambient air

eff Effective

elektr Electrical

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Table 2 (continued)

Index Meaning

f Lateral shading or with effect on radiation between a building element and the sky

F Frame

fac Due to appliances, machinery and equipment

g Glazing

goods Due to movement of goods (and/or materials)

h Space heating

i Internal (or from a specified layer inwards to the internal air)

I Internal, inside the building or space

in Input, entering

inf Infiltration

iu From a heated building zone to an unheated building zone

L Light

mth Month, e. g, per month, 1/mth; mth = Jan, Feb, March, Apr, May, June, July, Aug, Sept, Oct, Nov, Dec

max Maximum, largest

mech Mechanical (ventilation system)

min Minimum, smallest

NA Reduced heating operation (night-time set-back)

nutz During usage hours; usage-dependent

op Opaque

op Operating, operation

out Output, leaving

p Partition between building zone and sunspace

p At constant pressure (for cp,a)

P Caused by or relating to persons, metabolic

res Resulting

S Solar, due to solar radiation

s Ground

sink Heat sink

source Heat source

T Transmission

tb Partially heated

TI Transparent thermal insulation

tot Total, overall

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Table 2 (continued)

Index Meaning

tr Transparent

u Unheated or uncooled space or building zone

ue From unheated building zone to external air (also refer to subscript “e”)

V Ventilation

V,mech Mechanical ventilation

WB Thermal bridge

win Window

wirk Effective

we Weekend or holiday-period operating mode

x Represents states, elements or zones

z Adjacent building zone

ZUL Supply air of a mechanical ventilation system

j,k,l Serial variables

NOTE European standardized symbols and subscripts are used in Tables 1 and 2.

4 Relationship between the parts of the DIN V 18599 series of prestandards

The following two subclauses

⎯ summarize the input parameters to be used in this document, and

⎯ provide an overview of how the part-balances calculated using the method explained here are applied in other parts of the DIN V 18599 series of prestandards.

Subclause 4.3 contains a brief explanation of how the output parameters from the calculations described in this document are to be used for various types of technical building systems.

4.1 Input parameters from other parts of the DIN V 18599 series of prestandards

The following are required for the balance estimates:

⎯ Internal set-point temperature for heating ϑi,h,soll see DIN V 18599-10

⎯ Internal set-point temperature for cooling ϑi,c,soll see DIN V 18599-10

⎯ Average monthly external temperature ϑe see DIN V 18599-10

⎯ Permitted internal set-back temperature for reduced operation Δϑi,NA see DIN V 18599-10

⎯ Ratio of indirectly heated areas to the total area αtb see DIN V 18599-10

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⎯ Minimum external air volume flow per unit area AV& see DIN V 18599-10

⎯ Usage dependent minimum air change rate with external air nnutz see DIN V 18599-10

⎯ Daily operating time of the ventilation system tV,mech see DIN V 18599-10

⎯ Daily operating time of the heating system th,op,d see DIN V 18599-10

⎯ Number of usage days dnutz see DIN V 18599-10

⎯ Number of days in the month dmth see DIN V 18599-10

⎯ Heat dissipated by persons, appliances, machinery, equipment and lighting (residential use) qI see DIN V 18599-10

⎯ Heat dissipated by persons (metabolic heat) qI,p see DIN V 18599-10

⎯ Heat dissipated by appliances, machinery and equipment qI,fac see DIN V 18599-10

⎯ Mean solar irradiance for the respective month IS see DIN V 18599-10

⎯ Dirt depreciation factor FV see DIN V 18599-10

⎯ System-specific minimum supply air temperature ϑV,mech,RLT see DIN V 18599-3

⎯ Supply air temperature of the ventilation system of a residential building ϑWLA see DIN V 18599-6

⎯ Electrical energy for artificial lighting Qi,L,elektr see DIN V 18599-4

In addition, the following are needed for the final balance calculations:

⎯ Uncontrolled internal heat gains due to the heating system QI,h see DIN V 18599-5

⎯ Uncontrolled internal heat gains due to mechanical ventilation QI,rv see DIN V 18599-6

⎯ Uncontrolled cold gains due to mechanical ventilation QI,rv,c see DIN V 18599-6

⎯ Uncontrolled heat gains due to mechanical ventilation QI,vh see DIN V 18599-7

⎯ Uncontrolled heat gains due to the cooling system/cold generation QI,ch see DIN V 18599-7

⎯ Uncontrolled cold gains due to the cooling system (cooling and condenser water) QI,c see DIN V 18599-7

⎯ Uncontrolled cold gains due to mechanical ventilation QI,v,c see DIN V 18599-7

⎯ Uncontrolled heat gains due to the domestic hot water system QI,w see DIN V 18599-8

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The following are additionally needed for the design balance calculations:

⎯ Minimum internal temperature of heating operation for design calculations ϑi,h,min see DIN V 18599-10

⎯ Maximum permitted internal temperature on a design reference day for cooling ϑi,c,max see DIN V 18599-10

⎯ Daily mean external temperature on a design reference day for heating ϑe,min see DIN V 18599-10

⎯ Daily mean external temperature on a design reference day for cooling ϑe,max see DIN V 18599-10

⎯ Maximum hourly solar irradiance on a design reference day IS,max see DIN V 18599-10

⎯ Daily operating time of the cooling system tc,op,d see DIN V 18599-10

4.2 Output parameters for other parts of the DIN V 18599 series of prestandards

⎯ Energy need of the building zone for heating and estimated energy need for heating Qh,b,mth DIN V 18599-3 DIN V 18599-5 DIN V 18599-6

⎯ Energy need of the building zone for cooling and estimated energy need for cooling Qc,b,mth DIN V 18599-3 DIN V 18599-5 DIN V 18599-6

⎯ Maximum heat load, maximum heating power Qh,max, Qh,max,res DIN V 18599-3 DIN V 18599-5 DIN V 18599-6 DIN V 18599-7

⎯ Maximum cooling load, maximum cooling power Qc,max, Qc,max,res DIN V 18599-3 DIN V 18599-7

⎯ Heating hours (in the respective month) th DIN V 18599-5 DIN V 18599-6 DIN V 18599-7

⎯ Cooling hours (in the respective month) tc DIN V 18599-7

⎯ Minimum air volume flow of the mechanical ventilation system V⋅mech,b DIN V 18599-3

⎯ Reference internal temperature for determining the energy need for heating ϑi,h DIN V 18599-5

⎯ Reference internal temperature for determining the energy need for cooling ϑi,c DIN V 18599-5

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⎯ Air temperature in an adjacent unheated or uncooled building zone ϑu DIN V 18599-5

4.3 Determination of the energy use for various types of technical building systems according to the DIN V 18599 series of prestandards

The internal loads due to the heating and cooling system are determined in relation to the extent to which the capacity is utilized. This is done by determining the energy needs for heating and cooling in an initial balance estimate of the heat sources and sinks without these internal loads. The final balance calculations are then carried out after calculating the heat and cold gains from the heating and cooling systems.

The energy needs for heating and cooling calculated by the methods described in this document are the basis for the calculations of the energy use for heating and cooling described in the ensuing parts of the DIN V 18599 series, depending on the type of system involved:

⎯ for static (water-based) heating systems, in DIN V 19599-5;

⎯ for ventilation systems for residential buildings, in DIN V 18599-6;

⎯ for HVAC and cooling systems, in DIN V 18599-7;

⎯ for combined heat and power (cogeneration) systems, in DIN V 18599-9.

The energy needs for heating and cooling shall be subdivided where different heating or cooling systems (e.g. underfloor heating and radiators) are operated in parallel.

Air handling for buildings with ventilation and air conditioning systems is described in DIN V 18599-3. The calculations for pre-conditioning of the air in systems of this kind shall involve the handling of external air up to the point where a given state of supply air is reached which is not directly dependent on the current need in the building zone (i.e. up to the central air-handling plant). The pre-conditioned air (basic ventilation supply) shall be included as a heat sink or source in the balance for the building zone.

The energy needs of a building zone for heating and cooling calculated according to DIN V 18599-2 is the need which

⎯ in constant air volume systems, is to be met by an (additional) heating or cooling system in the building zone (e.g. by static or dynamic cooling coils, cooled ceilings, radiators, underfloor heating);

⎯ in variable air volume systems, would require a temporary increase in the supply air flow. This is additionally specified in the calculations of the energy need for air conditioning.

The energy use of constant air volume systems shall be calculated on the basis of the energy needs of the building zone for heating and cooling using methods described in DIN V 18599-5, DIN V 18599-7 or DIN V 18599-9, depending on the type of system being assessed. In the case of variable air volume systems, the energy needs of the building zone for heating or cooling are to be taken into account by an increased volume when calculating the energy need for air conditioning (see DIN V 18599-3); the energy use in this case shall be determined on the basis of the total energy need for air conditioning calculated according to DIN V 18599-7.

The maximum heat and maximum cooling loads calculated as described in Annex B and Annex C, respectively, are used to determine the extent to which the heating and cooling systems are utilized.

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5 Monthly balance calculation method

5.1 Principle of balance calculation method

5.1.1 Balance boundaries and calculation period

The space for which a balance is calculated is a building zone. Partitioning of buildings into zones is specified in DIN V 18599-1. The balance boundaries are formed by the elements of the thermal envelope enclosing the building zone. In the case of ventilation systems, the balance boundary for the supply air flow is the point where it enters the devices which reheat or recool the supply air as a function of the energy need in the building zone.

Usually, the calculations are to be carried out for an average day in each month. The daily mean values shall be used as boundary conditions. The daily values of all heat sources and sinks shall be calculated for each month. If different boundary conditions are foreseen for different days within the month (e.g. working days, weekends or holiday periods), the balances for these periods are to be calculated separately. Finally, the energy need for heating and cooling shall be summed up for each month.

The energy needs of a building zone for heating and cooling are the heat and cold gains which are required to maintain the specified internal temperature of the building zone and which are to be provided by the technical building installations within that zone. To calculate the energy needs of a building zone for heating and cooling, the external and internal heat and cold gains which are not controlled in relation to the internal temperature need to be balanced.

5.1.2 Heat sources and heat sinks

The heat flows within a building zone and at the boundaries of the zone are effective as heat sources (e.g. heat input, heat gains) or heat sinks (e.g. cold input, heat losses) for the respective zone. The sum of the heat sinks and the sum of the heat sources shall be put in relation to each other in order to establish the energy balance, from which the energy needs for heating and cooling are then determined.

The following heat sources and sinks shall be included in the energy balance (only sensible heat being taken into consideration):

⎯ transmission heat sinks or sources due to thermal conduction through the elements and heat transfer from and to the elements of the boundary surfaces of the building zone;

⎯ ventilation heat sinks or sources due to exchange of air in a space for external air (infiltration and window airing) and/or by air from other building zones;

⎯ ventilation heat sinks or sources due to air exchange in a space by means of ventilation systems, which usually introduce pre-conditioned supply air into the zone;

⎯ solar heat gains due to solar radiation entering the spaces through transparent elements;

⎯ heat sinks or sources due to solar radiation absorption and radiative heat transfer by the external surfaces of opaque elements;

⎯ internal heating or cooling due to the operation of (electrical) equipment, or due to artificial lighting, dissipation of heat by humans and animals (metabolic heat), introduction of hot or cold materials, goods and objects into the building zone, or the flow of heat media or refrigerants in distribution pipes and ducts;

⎯ during reduced operation at weekends or during holidays, the heat stored in the thermal envelope during the usage period that escapes during the set-back period.

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In buildings with cooling systems, the energy need for cooling shall be determined on the basis of the contribution of the heat sources not usable for heating purposes.

NOTE In buildings with heating systems only, the contribution of the heat sources not intended for heating will result in higher internal temperatures, or else is compensated by increasing the contribution of the heat sinks (e,g. by window airing).

5.1.3 Utilization of heat sources and heat sinks

Calculation of the usable heat contribution from heat sources on the basis of the utilization factor is an approximate method which takes into account the fact that the losses and gains due to heat sinks and sources vary within the calculation period and, in some cases, are greater or less at different times. Depending on the (Thermal) time constant of the building zone, the heat sources and sinks will compensate each other to a greater or lesser extent. As a result, the utilization factor of heat sources needs to take the following into account:

⎯ the heat capacity and the (specific) transmission heat transfer coefficient and ventilation heat coefficient of the building zone for the respective building time constant;

⎯ the ratio of heat sources to heat sinks during the calculation period;

⎯ the calculation period;

⎯ the internal temperature variations tolerated by the user(s) or permitted by the technical building system (a value of 2 K being assumed).

Figure 3 — Determination of the energy needs of a building zone for heating and cooling

5.1.4 Factors affecting the heat sources and heat sinks

Apart from the design of the building, the energy needs of a building zone for heating and cooling are also considerably affected by the climatic conditions at the building’s location, by the way in which the building is used, and by user behaviour.

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⎯ The heat flows due to transmission or ventilation heat sources and sinks depend on the mean internal temperature of the building zone assumed for the time period being considered, as well as on the mean temperatures of the adjacent areas or zones (e.g. outdoors or other building zones).

⎯ The heat flows due to ventilation by HVAC systems depend on the type of ventilation system used, with respect to both supply air temperature and volume flows.

⎯ The internal temperatures and air change due to window airing depend on user behaviour, meaning that a standardized user behaviour is to be assumed for comparative energy calculations (e.g. for energy certification purposes). For other calculations (e.g. for energy consultancy purposes), it is also permissible to use values adapted to the respective conditions.

5.2 Balance equations for calculating the energy needs of a building zone for heating and cooling

5.2.1 General

In principle, an average day in the month is to be used as the reference period for which the heat sources and sinks are to be balanced (calculation period). Where applicable, a separate balance shall be calculated for days on which the operating conditions are known to deviate significantly from the average (e.g. weekends, holiday periods etc.). The values pertaining to the days of normal usage and to the exceptions (weekends, holidays) are then to be added together.

The first step is to estimate the energy needs for heating and cooling, uncontrolled heat and cold gains from heating and cooling systems being ignored. The internal heating and cooling contributed by the heating and cooling systems shall then be calculated on the basis of the estimated energy needs for heating and cooling. Additional balances shall then be calculated iteratively, taking into consideration these internal heat and cold gains. The following equations apply to all steps in the balance calculation procedure.

5.2.2 Balance equations for calculating the energy need for heating

The energy need for heating shall initially be determined as a daily value (24-h value) for each month. The sum of all heat sinks shall be compared with the sum of all heat sources and the balance calculated by applying equation (1), taking the utilization factor into account. The stored heat that escapes during reduced operation shall be taken into account in the balance for weekends or holiday periods. The monthly energy need for heating is calculated by multiplying the result by the number of days in the month using equation (4); if necessary, the days with full usage and days with reduced operation are to be considered.

Qh,b = Qsink – η Qsource – ΔQC,b (1)

where

Qh,b is the energy need of the building zone for heating: Qh,b,nutz for usage days, and Qh,b,we for days of non-usage;

Qsink is the sum of the heat sinks in the building zone under the given boundary conditions, as described in 5.3;

Qsource is the sum of the heat sources in the building zone under the given boundary conditions, as described in 5.4;

ΔQC,b is the heat escaping from building elements during periods of reduced operation at weekends and during holiday periods, according to 5.2.4 (ΔQC,b= 0 for continuous operation);

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η is the monthly utilization factor of the heat sources (for heating purposes), calculated according to 5.5.

5.2.3 Balance equations for calculating the energy need for cooling

The energy need for cooling on the basis of one day shall be calculated using equation (2). This is the contribution made by heat sources in excess of the actual energy need (surplus heat). Generally, different boundary conditions (e.g. different reference internal temperatures) are assumed to apply for heating and for cooling applications, so that heat sources and sinks are to be determined separately for heating and cooling. Depending on the boundary conditions, the heat sources and sinks may differ considerably from those observed in the calculations of the energy need for heating. The monthly energy need for cooling is calculated by multiplying the result by the number of days in the month using equation (5); if necessary, the days of full usage and days with reduced operation shall be taken into consideration.

Qc,b = (1 – η) Qsource (2)

where

Qc,b is the energy need of the building zone for cooling: Qc,b,nutz for usage days and Qc,b,we for days of non-usage;

Qsource is the sum of heat flows due to heat sources in the building zone under the given boundary conditions, as described in 5.4;

η is the monthly utilization factor of the heat sources (for heating purposes) as described in 5.5.

5.2.4 Accounting for weekend and holiday-period operation

For non-residential buildings, it may be necessary to account for days on which usage differs considerably (e.g. in periods of reduced operation at weekends or during holidays). In these cases, the following parameters may differ:

⎯ set-point temperature;

⎯ occupancy of the building zone and internal heat sources (or sinks);

⎯ usage-dependent and mechanical (ventilation-driven) air change rates;

⎯ daily heating or cooling times;

⎯ activation of solar protection devices.

The balances for the energy need for heating and the energy need for cooling shall be calculated separately for both workdays and weekends. In some cases, this may mean that heat sources, heat sinks and the utilization factor need to be calculated individually for four different sets of boundary conditions (heating/cooling; workdays/weekends). The values obtained shall be projected onto a month in relation to their respective share of the total operating time in order to obtain monthly values (see equations (6) and (7)).

5.2.4.1 Balance of the energy need for heating

When considering reduced heating operation, the mean internal temperature for days of non-usage shall be determined using equation (30).

The heat stored in the thermal envelope area during periods of normal usage that escapes during periods of reduced operation shall be taken into account as follows:

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⎯ In the balance for days with normal usage or with continuous usage:

in equation (1) ΔQC,b = ΔQC,b,nutz = 0 and

in equation (11) ΔQC,sink = ΔQC,sink,nutz shall be assumed as specified in 6.6.

⎯ In the balance for days with weekend or holiday operation:

in equation (1) ΔQC,b = ΔQC,b,we shall be assumed as specified in 6.6 and

in equation (11) ΔQC,sink = ΔQC,b,we = 0

NOTE In order to determine the stored heat, the balance for the weekend should be calculated first.

5.2.4.2 Balance of the energy need for cooling

Where ventilation and/or air conditioning cooling systems are turned off at weekends or during holiday periods, the following can be assumed:

Qc,b,we = 0 (3)

Transfer of heat between the days of usage and non-usage is neglected.

In equation (11) ΔQC,sink = 0.

5.2.5 Monthly values and annual values

The monthly energy need for heating and the monthly energy need for cooling are calculated by projecting the daily sums onto a full month:

For residential buildings and buildings with continuous operation:

Qh,b,mth = dmth Qh,b (4)

Qc,b,mth = dmth Qc,b (5)

where

dmth is the number of days in the month;

Qh,b is the balanced energy need of the building zone for heating;

Qc,b is the balanced energy need of the building zone for cooling.

For building zones with different operating modes, the values for days with normal usage (e. g. operating days) and the values for days with reduced usage (e.g. holidays or weekends) shall be calculated in relation to their share of the whole month.

Qh,b,mth = dnutz Qh,b,nutz + dwe Qh,b,we (6)

Qc,b,mth = dnutz Qc,b,nutz + dwe Qc,b,we (7)

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where

dnutz is the number of days in the month on which the building zone is in normal usage (usually the following applies: dnutz = dnutz,a/365 dmth, where dnutz,a is the number of usage days per year according to DIN V 18599-10);

Qh,b,nutz is the balanced energy need of the building zone for heating under normal conditions of usage;

Qc,b,nutz is the balanced energy need of the building zone for cooling under normal conditions of usage;

dwe is the number of days in the month with no or with reduced usage (e.g. weekends, holidays) taking equation (8) into account;

Qh,b,we is the balanced energy need of the building zone for heating under the conditions existing with no usage or with reduced usage (e.g. weekends, holidays);

Qc,b,we is the balanced energy need of the building zone for cooling under the conditions existing with no usage or with reduced usage (e.g. weekends, holidays).

The total number of days in the month is

dnutz + dwe = dmth (8)

If specific pre-specified holiday periods and public holidays are known, these may be taken into consideration for each individual month when calculating the balances. In such cases, public holidays and holiday periods are to be shown separately.

NOTE The number of operating days of a VAC system, dV,mech (see DIN V 18599-3), corresponds to dnutz or, in the calculations for weekend set-back operation, to dwe.

The annual energy need of the building zone for heating Qh,b,a shall be calculated by adding together the values calculated for each month. The annual energy need of the building zone for cooling Qb,c,a shall be calculated accordingly.

Qh,b,a = ∑mth

mthb,h,Q (9)

Qc,b,a = ∑mth

c,b,mthQ (10)

where

Qh,b,a is the annual energy need of the building zone for heating;

Qh,b,mth is the monthly energy need for heating;

Qc,b,a is the annual energy need of the building zone for cooling;

Qc,b,mth is the monthly energy need for cooling.

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5.3 Heat sinks

5.3.1 General

The total amount of heat sinks Qsink is the sum of the transmission and ventilation heat sinks (heat losses) and cold gains from ventilation systems, internal sources of cold in the building zone and radiation losses.

Qsink = QT + QV + QI,sink + QS + ΔQC,sink (11)

where

Qsink is the sum total of heat sinks in the building zone;

QT is the heat flow due to transmission heat sinks calculated according to 5.3.2;

QV is the heat flow due to ventilation heat sinks calculated according to 5.3.3;

QI,sink is the heat flow due to internal heat sinks in the building zone calculated according to 5.3.4;

QS is the heat flow due to radiative heat transfer, taking into account incident solar radiation (see 5.3.5)

ΔQC,sink is the heat stored during periods of normal operation that escapes from the elements during days with reduced operation (see 5.3.6). In the heating energy balance it shall only be taken into account for the days during which the zone is in use.

5.3.2 Transmission heat sinks

Depending on the temperatures on both sides of a building element, the transmitted heat flow will act either as a heat source or as a heat sink. If a building zone is adjacent to various areas with differing temperature levels, it is possible that transmission heat sources and transmission heat sinks may exist at the same time. Transmission heat sinks will occur in all boundaries with adjacent areas in which the mean temperatures are lower than the internal temperature of the building zone being considered. Generally this includes above all transmission of heat to the external environment. Transmission heat sinks are generally to be calculated using equation (12):

∑ −=j

jj tHQ )( iT,T ϑϑ for ϑi > ϑj (12)

where

HT,j is the transmission heat transfer coefficient between the building zone and an adjacent area;

ϑi is the reference internal temperature of the building zone according to 6.1;

ϑj is the average monthly external temperature or the mean temperature of an adjacent zone;

t is the length of the calculation step (t = 24 h).

The transmission heat transfer coefficient HT,j shall be calculated from the thermal transmittance of the individual elements and their areas as specified in DIN EN ISO 13789 and DIN EN ISO 13370, taking into account linear and point thermal bridges. For simplification, a default value may be assumed for the effect of the thermal bridges.

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Wherever the temperature of the adjacent zone is lower than the internal temperature of the building zone being assessed, the following transmission heat flows are to be taken into account:

⎯ transmission through external building elements

QT,e = HT,D (ϑi – ϑe) t (see equation (42))

⎯ transmission to adjacent unheated building zones or sunspaces

QT,u = HT,iu (ϑi – ϑu) t (see equation (46))

⎯ transmission to adjacent heated or cooled building zones

QT,z = HT,iz (ϑi – ϑz) t (see equation (50))

⎯ transmission to the ground

QT,s = HT,s (ϑi – ϑe) t (see equations (53) and (55)).

5.3.3 Ventilation heat sinks

Ventilation heat flow is caused by infiltration through gaps and leaks, window airing or mechanical ventilation systems. In each case, the air entering the building zone needs to be balanced. Depending on the temperature of the air entering the zone, the air stream will constitute either a heat sink or a heat source. If a building zone is adjacent to various areas with differing temperature levels, the different air streams may cause ventilation heat sources and ventilation heat sinks at the same time. The heat flow due to ventilation heat sinks is generally to be calculated using equation (13):

( )∑ −=k

kk tHQ ϑϑiV,V for ϑi > ϑk (13)

where

HV,k is the heat transfer coefficient for ventilation by external air, air from another building zone or via a ventilation system (see 6.3);

ϑi is the reference internal temperature of the building zone as specified in 6.1;

ϑk is the average monthly external temperature, or the mean temperature of the air from the other building zone or the mean air temperature of the air supplied by the ventilation system;

t is the period to which the calculation step applies (t = 24 h).

The heat transfer coefficient HV,k is calculated from the mean volume flow, the specific heat capacity of air and the density of air. The mean volume flow is usually given as the product of the mean number of air changes and the volume of the building zone (see 6.3).

In particular, the following ventilation heat sinks shall be taken into consideration if the mean temperature of the air entering the zone is lower than the internal air temperature of the zone:

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⎯ Ventilation heat sinks due to external air infiltration

External air can enter the building zone through gaps, joints and leaks in external building elements (infiltration). Infiltration depends on the way the building is constructed, in particular its airtightness (e.g. on the extent of leaks and their distribution in the building envelope). As the internal temperature is generally higher than the mean external air temperature, infiltration of external air generally has the effect of a heat sink in the building zone.

QV,inf = HV,inf (ϑi – ϑe) t (see equation (56))

⎯ Ventilation heat sinks due to window airing

Replacement of internal air by external air entering through windows, doors or other envelope openings which can be opened and shut depends on the usage of the building zone and is generally variable. Here too, this air change generally constitutes a heat sink:

QV,win = HV,win (ϑi – ϑe) t (see equation (64)

⎯ Cold gains due to mechanical ventilation

Cold gains due to HVAC systems shall be taken into consideration in the building zone if these occur independently of the current heat or cooling load. This is the case, for example, with residential ventilation systems and ventilation systems with central air handling. For demand-oriented variable air volume control (VAV) systems, the minimum volume flow shall be assumed. When calculating the cold gains due to supply air, the difference between the supply air temperature and the reference internal temperature, as well as the operating time of the ventilation system, shall be taken into consideration. The supply air temperature is generally specified for systems with temperature control and for ventilation systems of residential buildings.

QV,mech = HV,mech (ϑi – ϑV,mech) t (see equation (81))

For building zones not equipped with mechanical ventilation:

QV,mech = 0 (14)

⎯ Ventilation heat sinks due to air exchange with other zones

Where there is a high rate of air exchange between different spaces or enclosures in a building, these shall be grouped together as a single building zone. Thus the air exchange between building zones is generally assumed to be zero. If, in individual cases, there are two zones with air exchange between the zones, then the heat sink due to air entering the zone shall be calculated for the zone into which the air flows, using equation (13) and inserting the appropriate values (cf. also 6.3.5). This may be necessary, for instance, in zones with extract air systems where the replacement air is drawn in from other zones.

QV,z = HV,z (ϑi – ϑz) t (see equation (97))

5.3.4 Internal heat sinks

Internal heat sinks (sources of cold) may exist in the building zone in the form of refrigerant piping, cold-water pipes or cold-air ducts located within the zone. “Losses” due to distribution piping and air ducts and their proportional impact on a building zone shall be calculated according to DIN V 18599-7.

Cold (i.e. heat losses) can also be due to equipment (e.g. chilled counters with external cold generation, split units) or due to cold materials or objects (e.g. production materials) being regularly brought into the building zones.

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It is possible for internal heat sinks and internal heat sources to exist simultaneously within a building zone.

The total internal heat sinks shall be calculated as follows:

QI,sink = QI,sink,c + QI,sink,fac + QI,sink,goods (15)

where

QI,sink,c is the input of cold due to cooling systems according to 6.5.6 (due to distribution piping and air ducts with temperatures below the internal temperature);

QI,sink,fac is the input of cold due to appliances, equipment and machinery according to 6.5.3;

QI,sink,goods is the input of cold due to materials and goods with temperatures below internal temperature brought into the building zone, according to 6.5.4.

In the initial balance estimates (see DIN V 18599-1), the value of QI,sink,c shall be assumed to be zero.

5.3.5 Heat sinks due to radiative heat transfer

The heat gains due to solar radiation on opaque surfaces shall be balanced against the heat losses due to long-wave radiative heat transfer from these surfaces. This may cause a heat sink if the solar radiation levels are low and the radiative heat transfer levels are high. The respective heat flows cause each building element to act as either a heat source or a heat sink.

QS,op shall be calculated as described in 6.4.2.

5.3.6 Heat storage

When taking into account reduced operation at weekends or during holidays, the heat stored in elements during periods of normal operation that escapes during the period of reduced operation and is stored in days with normal operation shall be taken into account. For days of non-usage this heat is to be deducted directly from the energy need for heating, for usage days this heat shall be treated as a heat sink.

Heat transfer is only taken into account when considering the energy need for heating. The following applies:

⎯ when calculating the balance of the energy need for heating for usage days:

ΔQC,sink as in 6.6;

⎯ when calculating the balance of the energy need for heating for days of non-usage:

ΔQC,sink = 0;

⎯ when calculating the balance of the energy need for cooling for days of usage and non-usage:

ΔQC,sink = 0.

5.4 Heat sources

5.4.1 General

The total amount of heat sources Qsource is the sum of heat flows due to solar radiation, transmission heat sources, ventilation heat sources due to natural and mechanical ventilation and internal heat sources within the building zone.

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Qsource = QS + QT + QV + QI,source (16)

where

Qsource is the sum of heat sources in the building zone;

QS is the sum of heat flows due to solar radiation calculated according to 5.4.2;

QT is the sum of heat flows due to transmission heat sources calculated according to 5.4.3;

QV is the sum of heat flows due to ventilation heat sources calculated according to 5.4.4

QI,source is the sum of heat flows due to internal heat sources in the building zone calculated according to 5.4.5.

5.4.2 Heat sources due to solar radiation

Solar radiation can be absorbed directly within the building zone if it enters via windows or other transparent building elements, or it can be absorbed on the external envelope by opaque building elements and then act indirectly as a heat source as a result of heat being conducted into the building zone. The sum of solar heat gains shall thus be calculated for all element surfaces as follows:

QS = Σ QS,tr + Σ QS,op (17)

where

QS,tr is the sum of heat gains due to solar radiation through transparent building elements;

QS,op is the sum of the heat gains due to solar radiation on opaque surfaces.

⎯ Heat sources due to solar radiation entering through transparent surfaces

The quantity of heat QS,tr gained due to solar radiation entering the heated or cooled building zone via windows etc. shall be calculated as follows:

QS,tr = FF A geff IS t (see equation (105))

The solar irradiance IS is the respective monthly mean intensity of incident solar radiation on the surface as a function of the inclination and orientation of that surface. The unfinished (raw carcass) area of the element is used as the area A. This is then reduced by multiplying it by the frame factor FF to take into account the opaque frames. The effective total energy transmittance geff of the transparent part of the surface shall also take into consideration the following factors which reduce the amount of radiation on and through the element:

⎯ the energy transmittance of the glazing;

⎯ any solar protection devices installed;

⎯ mode of solar protection device control;

⎯ shading by other buildings or parts of the building, as well as shading from the horizon.

The effect of solar protection devices which are controlled automatically or manually shall be calculated in relation to how these are likely to be activated.

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⎯ Heat sources due to solar radiation on opaque surfaces

In order to determine the heat sources due to solar radiation on opaque building elements, the radiation absorbed by the element shall be balanced against the radiative heat transfer from that element. The proportion of absorbed radiation which is effective within the building zone depends on the thermal resistance inwards and outwards from the absorbent layer.

Depending on the type of building element (e.g. external wall, external wall with transparent thermal insulation), different calculation methods will need to be applied.

The following heat sources due to solar radiation are specified:

⎯ QS,op radiation on opaque building elements without transparent thermal insulation, to be calculated using equation (110);

⎯ QS,op,TI radiation on opaque building elements with transparent thermal insulation, to be calculated using equation (113).

⎯ Heat sources due to solar radiation passing through or into unheated glazed sunspaces.

Solar heat gains due to radiation passing through sunspaces are to be determined as described in 6.4.3, whereby the external glazing of the sunspace is also to be taken into account. To enable calculation of the temperature inside the sunspace (this being required for the calculations of transmission heat flow and ventilation heat flow), the solar heat gains inside the sunspace shall be determined.

Until there is a generally accepted method of calculation, solar heat gains through glass double façades with divisions at every storey can be calculated using the methods generally applied to unheated sunspaces, but using special boundary conditions.

5.4.3 Transmission heat sources

The transmission heat flows through any building element will depend on the temperatures on either side of the element (i.e. they may constitute either heat sources or heat sinks). They act as heat sources if the mean temperature in the adjacent zone is higher than the internal temperature of the building zone being assessed.

If the building zone is adjacent to various areas with differing temperature levels, there may be both transmission heat sinks and transmission heat sources at the same time.

Equation (18) is generally used to calculate the heat flows due to transmission heat sources:

∑ −=j

jj tHQ )( iT,T ϑϑ for ϑi < ϑj (18)

where

HT,j is the heat transfer coefficient between the building zone and an adjacent area;

ϑi is the reference internal temperature of the building zone according to 6.1.

ϑj is the average monthly external temperature or the mean temperature of the adjacent building zone;


The heat transfer coefficient HT,j shall be calculated from the thermal transmittance of the individual elements and their surface areas as specified in DIN EN ISO 13789 and DIN EN ISO 13370, taking into account linear

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and point thermal bridges. For simplification, a default value may be assumed for the effect of the thermal bridges.

Wherever the temperature of the adjacent area is higher than the internal temperature of the building zone being evaluated, the following transmission heat flows shall be taken into consideration:

⎯ Transmission through external building elements

Since the mean external temperature is usually lower than the internal temperature, this source only needs to be taken into consideration in exceptional cases.

QT,e = HT,D (ϑe – ϑi) t (see equation (43))

⎯ Transmission from adjacent unheated building zones or sunspaces

QT,u = HT,iu (ϑu – ϑi) t (see equation (47))

⎯ Transmission from adjacent heated or cooled building zones

QT,z = HT,iz (ϑz – ϑi) t (see equation (51))

⎯ Transmission through the ground

QT,s = HT,s (ϑe – ϑi) t (see equation (54) and equation (55)).

5.4.4 Ventilation heat sources

Heat sources due to ventilation can be caused, for example, by the heated supply air in a ventilation system with air heating. Where, in exceptional cases, the average external temperature is higher than the internal temperature, the infiltration of external air as well as window airing also constitutes a heat source (e.g. when calculating the maximum cooling load, see Annex C). If a building zone is adjacent to various areas with differing temperature levels, there may be both ventilation heat sources and ventilation heat sinks at the same time.

Heat flows due to ventilation heat sources are generally calculated using equation (19):

∑ −=k

kk tHQ )( iV,V ϑϑ for ϑi < ϑk (19)

where

HV,k is the heat transfer coefficient due to ventilation to external air, air in another building zone, or via a ventilation system (see 6.3);

ϑi is the reference internal temperature of the building zone according to 6.1;

ϑk is the monthly average external temperature or the mean temperature of the supply air from the ventilation system or from another building zone;

t is the calculation period.

The heat transfer coefficient HT,j is calculated from the mean volume flow, the specific heat capacity of air and the density of air. The mean volume flow is usually given as the product of the mean air change rate and the volume of the building zone (see 6.3).

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In particular, the following ventilation heat sources shall be taken into consideration if the mean temperature of the air entering the zone is higher than the internal air temperature of the zone:

⎯ Ventilation heat sources due to external air infiltration


QV,inf = HV,inf (ϑe – ϑi) t (see equation (57))

⎯ Ventilation heat sources due to window airing


QV,win = HV,win (ϑe – ϑi) t (see equation (65))

⎯ Heat sources due to mechanical ventilation

Heat input due to HVAC systems shall be taken into consideration in the building zone if they are applied independently of the current heating or cooling load. This applies, for example, to ventilation systems for residential buildings and to ventilation systems with central air handling. Air heating systems are generally demand-controlled systems and, as such, need not be included in the calculations described here. For variable air volume systems controlled as a function of the heat load, the minimum volume flow shall be assumed. Calculation of heat input due to supply air from a mechanical ventilation system shall take into account the difference between the supply air temperature and the internal temperature, as well as the operating time of the ventilation system. The supply air temperature is generally specified for systems with temperature control and for ventilation systems in residential buildings.

QV,mech = HV,mech (ϑV,mech – ϑi) t (see equation (82))

Equation (14) applies to spaces without mechanical ventilation systems:

QV,mech = 0

⎯ Ventilation heat sources due to air exchange with other zones

Where there is a high rate of air exchange between different spaces or enclosures in a building, these are generally to be grouped together into a single building zone. Thus the air exchange between building zones is generally to be assumed to be zero.

If, in exceptional cases, there are two zones with air exchange between the zones, then equation (19) with the appropriate values shall be used to calculate the heat source resulting from air entering the zone into which the air flows (see also 6.3.5). This may be necessary, for instance, in zones with extract air systems where the replacement air is drawn in from other zones.

QV,z = HV,z (ϑz – ϑi) t (see equation (98)).

5.4.5 Internal heat sources

Internal heat sources include persons and animals in the building zone, (electrical) appliances and equipment operated within the zone and, in particular, artificial lighting. Internal heat sources may exist in the building zone in the form of central heating distribution pipes, domestic hot water pipes, hot-air ducts and/or heat storage units, heaters or chillers located within the zone, or they may be due to hot materials or objects (e.g. production materials) being regularly brought into the building zones. The “losses” from distribution pipes and air ducts shall be determined using the methods described in DIN V 18599-5 to DIN V 18599-8. The heat

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sources due to artificial lighting are to be calculated as described in DIN V 18599-4, also taking subclause 6.5.3 of this standard into account. There may be both internal heat sinks and internal heat sources within a building zone at the same time.

The internal heat sources shall be added together as follows:

QI,source = QI,source,p + Q I,source,L + Q I,source,fac + Q I,source,goods + Q I,source,h (20)

where

QI,source,p is the heat input due to persons according to 6.5.2;

QI,source,L is the heat input due to artificial lighting according to 6.5.5;

QI,source,fac is the heat input due to equipment, machinery or other appliances as described in 6.5.3;

QI,source,goods is the heat input due to material, goods and objects brought into the building zone and which have temperatures above the reference internal temperature, as described in 6.5.4;.

QI,source,h is the heat input due to heating and cooling systems as described in 6.5.6 (due to distribution pipes and air ducts with temperatures higher than the reference internal temperature, as well as heat input due to generation and storage).

In the initial balance estimates (see DIN V 18599-1) the value of QI,source,h shall be assumed to be zero.

For residential buildings, an estimated total value for the internal heat sources QI,source,p, QI,source,L, QI,source,fac and QI,source,goods can be assumed (see DIN V 18599-10). However, the heat sources QI,source,h due to distribution pipes and air ducts shall be determined separately, even for residential buildings.

5.5 Utilization of the heat sources

5.5.1 General

The utilization factor shall first be approximated, neglecting the internal heat and cold input due to heating and cooling systems. The energy needs for heating and cooling in the building zone thus estimated are then used to quantify these internal heat sources and sinks. Once all internal heat sources and sinks have been fully determined, the value of the utilization factor shall be calculated by iteration.

The utilization factor η greatly depends on the ratio γ of the heat flows due to the heat sources and the heat flows due to the heat sinks in the building zone. Since different boundary conditions generally apply as a function of the heating operation, cooling operation, usage days and non-usage days, the utilization factor shall be determined separately for each of these cases, depending on the respective ratios of heat sources to heat sinks.

sink

sourceQ

Q=γ (21)

A further parameter to be taken into consideration when determining the utilization factor is the (thermal) time constant τ of the building zone (see 6.7.2).

NOTE The utilization factor makes due allowance for a temperature difference of 2 K above the internal set-point temperature, i.e. heat sources are considered to be "usable" as long as the internal temperature is not higher by more than 2 K. Where this is exceeded, it is assumed that the surplus heat is not usable for room conditioning and is dissipated

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(e.g. by additional ventilation). In the case of cooling operation, this means that additional heat gains are not compensated for by the cooling system unless the temperature exceeds the set-point by 2 K.

5.5.2 (Thermal) time constant of the building zone

The (thermal) time constant τ is calculated on the basis of the effective heat capacity of the building zone and the sum of the transmission and ventilation heat transfer coefficients of the zone, including the ventilation heat transfer coefficient due to a mechanical ventilation system.

HCwirk=τ (22)

where

Cwirk is the effective heat capacity as specified in 6.7.1;

H is the overall transmission and ventilation heat transfer coefficient, including heat transfer from mechanical ventilation.

The overall heat transfer coefficient is the sum of the transmission and ventilation heat transfer coefficients:

H = HT + HV = ∑j

jHT, + ∑k

kH V, + HV,mech,ϑ (see 6.7.2)

5.5.3 Utilization factor

The utilization factor η is determined by approximation on the basis of the ratio γ of heat sources to heat sinks, as follows:

111

+−

−= a

a

γγη if γ ≠ 1 (23)

and

1+=

aaη if γ = 1 (24)

Here, a is a numerical parameter accounting for the (thermal) time constant of the building zone.

00 τ

τ+= aa (25)

NOTE a0 and τ0 are constant (see 6.7.3).

Where there is mechanical ventilation with a high air change rate, the utilization factor shall be assumed to be equal to 1 (see 6.7.3).

6 Determination of individual parameters for the monthly balance

6.1 Room temperature assumptions

The room temperatures to be assumed when calculating the balances are mean values relating to space and time. The mean value relating to space (“space-averaged”) is a value averaged over the reference area of the

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building zone being assessed. In buildings used for residential purposes only, this is the total net floor area of the building. Different methods shall be used to calculate the mean value related to time (“time averaged”), depending on what the result is to be used for (monthly balance, design calculations, heating mode, cooling mode). Apart from being based on the internal set-point temperature, the reference temperature shall take several other factors into account. The various temperatures to be used in the calculations are listed below:

a) Internal set-point temperature for heating (monthly mean value) ϑi,h,soll

The internal set-point temperature for heating is the minimum room temperature which is to be maintained during periods of normal usage, and is specified in DIN V 18599-10.

b) Internal set-point temperature for cooling (monthly mean value) ϑi,c,soll

The internal set-point temperature for cooling is the mean temperature of a room which is to be maintained during periods of normal usage while the cooling system is in operation. Following normal practice in cooling system control, it is assumed that higher temperatures will be permitted in rooms when the external temperatures are higher; therefore a mean value is used here. The internal set-point temperature for cooling is specified in DIN V 18599-10.

c) c) Minimum temperature (design, for heating) ϑi,h,min

The minimum temperature is the minimum temperature of a room which is to be maintained at the design external temperature. This may be lower than the monthly internal set-point temperature. The minimum temperature is specified in DIN V 18599-10.

d) Maximum temperature (design, for cooling) ϑi,c,max

The maximum temperature is the maximum temperature of a room permitted at the design maximum external temperature. It is generally higher than the monthly internal set-point temperature for cooling. The maximum temperature is specified in DIN V 18599-10.

e) Reference internal temperature ϑ i,h for calculating the energy need for heating

The reference internal temperature is the temperature used as a reference for the balance calculations. The 24-hour mean value for each month is to be used. Hence the reference internal temperature for heating shall also take into consideration any reduction in heat output at night. A separate reference internal temperature shall be determined for heating during weekends or holiday periods. In cases where the heat output is not reduced during the night, the reference internal temperature shall be equal to the internal set-point temperature for heating.

When calculating the balances, a variation of +2 K in the room temperature is permitted, and is taken into account by the heating utilization factor (see 6.1.1).

f) Reference internal temperature ϑ i,c for calculating the energy need for cooling

The reference internal temperature is the temperature taken as a reference for the balance calculations. The 24-hour mean value for each month shall be used.

As the utilization factor used in the balance calculations takes into account a permitted variation in room temperature of 2 K, a reference temperature 2 K lower than the set-point room temperature for cooling shall be assumed for cooling (see 6.1.2).

g) Temperature ϑu in adjacent unheated or uncooled building zones

The temperature in adjacent unheated or uncooled building zones depends on the reference internal temperature of the building zone being considered and the external temperature, as well as on the heat transfer coefficients of the boundaries between the zone and the unheated space and between the unheated space and the external environment. This temperature can be approximated using correction factors (see 6.1.3).

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h) Temperature ϑ z of adjacent heated or cooled zones

Provided heat transfer occurs between adjacent zones, the temperature of an adjacent heated or cooled zone shall be assumed to be the reference internal temperature of the respective zone, i.e. in heating applications the reference internal temperature for heating, and in cooling applications the reference internal temperature for cooling (see 6.1.4).

i) Reference internal temperature ϑ i,h,min for calculating the maximum heating power

The minimum temperature as specified in DIN V 18599-10 shall be used (see c)) to calculate the maximum heating power.

j) Reference internal temperature ϑ i,c,max,d for calculating the maximum cooling power

The mean of the maximum permitted temperature ϑ i,c,max at design conditions and reference internal temperature ϑ i,c shall be taken as the daily mean value for calculating the maximum cooling power.

6.1.1 Reference internal temperature for calculating the energy need for heating

In the monthly balance calculation of the energy need for heating, the mean monthly value of the internal set-point temperature ϑ i,h,soll for heating as specified in DIN V 18599-10 should generally be used. To make allowance for reduced heating operation in certain spaces or at certain times, the room temperature shall be corrected by applying equations (27), (30) or (33). For continuous operation (24-hour usage), the following shall apply:

ϑi,h = ϑi,h,soll (26)

6.1.1.1 Reduced heating at night

If the calculations are to make allowance for reduced heating operation during the night, equation (27) shall be used to correct the monthly internal temperature. All times during which the room temperature is allowed to be lower than the normal internal set-point temperature are considered to be periods of reduced heating operation. A distinction is made between the following modes of reduced heating operation:

⎯ Set-back mode: lowering the heating supply temperature for a pre-specified period at night-time;

⎯ Switch-off mode: shutting down the heating system for a pre-specified period at night-time; this period includes associated set-back and boost mode times.

In both cases, only a temperature reduction up to the specified maximum temperature set-back (Δϑ i,NA) may be used in the calculations.

The reference internal temperature for days with specified usage times (workdays) shall be determined monthly as a function of the external temperature. However, at least the time-weighted mean temperature of normal operation and maximum night-time temperature set-back Δϑ i,NA as specified in DIN V 18599-10 shall be used in the balance equations.

⎟⎠

⎞⎜⎝

⎛ −−−=h 24

),(max NANAi,sollh,i,esollh,i,NAsollh,i,hi,

tf ϑΔϑϑϑϑϑ (27)

where

fNA is the correction factor for reduced night-time heating operation according to equation (28) or (29);

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ϑ i,h,soll is the internal set-back temperature in the normal heating mode according to DIN V 18599-10;

ϑe is the monthly average external temperature;

Δϑ i,NA is the permitted internal set-back temperature for reduced heating operation according to DIN V 18599-10;

tNA is the daily reduced heating time, the boost heating period being counted as being part of the operating time (tNA = 24 h – th,op,d; where th,op,d is the daily operating time of the heating system according to DIN V 18599-10).

The correction factor fNA shall be calculated as follows:

⎯ for set-back mode:

⎟⎠⎞

⎜⎝⎛−=

h 250exp

h 2413,0 NA

NAτtf (28)

⎯ for switch-off mode:

⎟⎠⎞

⎜⎝⎛−=

h 250exp

h 2426,0 NA

NAτtf (29)

where

τ is the (thermal) time constant of the building zone as described in 6.7.2.

6.1.1.2 Reduced heating operation during weekends and holiday periods

In order to take into account reduced heating operation during weekends and holiday periods, additional balance calculations of the monthly energy need for heating shall be carried out with the boundary conditions relating to weekend and holiday-period operation. The energy need for heating in normal operation and in weekend and holiday-period operation shall then be added together (see 5.2.4).

In the same way as for reduced heating operation at night, a distinction shall be made between set-back mode (with reduced heating supply temperature) and switch-off mode (with controlled set-back and boost mode periods). The temperature set-back on days on which the building zone is not used shall be not greater than the maximum night-time temperature set-back Δϑ i,NA as in DIN V 18599-10.

Equation (30) shall be used to determine the monthly internal temperature for calculating the monthly energy need for heating for the days on which the zone is not used or only partially used (i.e. at weekends and during holiday periods).

ϑ i,h = max (ϑ i,h,soll – fwe (ϑ i,h,soll – ϑe), ϑ i,h,soll – Δϑ i,NA) (30)

where

fwe is the correction factor for reduced heating operation over a period of more than one day, obtained from equation (31) or (32);

ϑ i,h,soll is the internal set-point temperature in the normal heating mode as specified in DIN V 18599-10;

ϑe is the monthly average external temperature;

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Δϑ i,NA is the permitted set-back of the internal temperature for reduced heating operation as in DIN V 18599-10.

The correction factor fwe shall be calculated as follows:

⎯ for set-back mode:

⎟⎠⎞

⎜⎝⎛ −=

h 2504,012,0we

τf (31)

⎯ for switch-off mode:

⎟⎠⎞

⎜⎝⎛ −=

h 2502,013,0we

τf (32)

where

τ is the (thermal) time constant of the building zone as described in 6.7.2.

6.1.1.3 Partial heating (spatially reduced heating operation)

Partial heating of buildings which are only heated and which are calculated as a single zone (mainly residential buildings) can be taken into account using the mean internal temperature of the directly heated and indirectly heated areas of the building or zone. Indirectly heated areas are separate spaces which are heated indirectly via the heated area, but in which the temperature is allowed to remain below the internal set-point temperature (see DIN V 18599-10). DIN V 18599-10 specifies a default value to represent the proportion of indirectly heated area in residential buildings.

The reference internal temperature shall be calculated using equation (33)

ϑ i,h = ϑ i,h,soll – ftb (ϑ i,h,soll – ϑe) (33)

where

ftb is the correction factor for partial heating from equation (34);

ϑ i,h,soll is the mean internal temperature in the normal heating mode as in DIN V 18599-10;

ϑe is the monthly mean external temperature.

The correction factor ftb shall be calculated as follows:

2tb2

B

h,maxtb

W/m35exp18,0 a

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛−−=

A

Qf

& (34)

where

Q⋅h,max is the maximum heating power in the building zone (see Annex B);

AB is the area of the building zone (reference area);

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atb is the proportion of the total area taken up by the indirectly heated area, whereby atb shall not be more than 0,5; if atb is not specified in DIN V 18599-10, then it shall be calculated as follows:

B

mitbeheizttb A

A=a

where

Amitbeheizt is the indirectly heated area (area in which the temperature is allowed to drop below the set-point temperature) within the total area of the building zone;

AB is the total area of the building zone (reference area).

6.1.1.4 Combination of partial heating and reduced heating

Equation (35) shall be used to calculate the reference internal temperature for buildings comprising a single zone (residential buildings) with partial heating and reduced heating operation at night. This shall be obtained by replacing the internal temperature for normal operation ϑ i,h,soll in Equation (33) by the calculated internal temperature ϑ i,h taking into account night-time set-back or switch-off, obtained using equation (27).

ϑ i,h = ϑ i,NA – ftb (ϑ i,NA – ϑe) (35)

where

ϑ i,NA is the reference internal temperatureϑ i,h taking into account night-time set-back, obtained by equation (27).

6.1.2 Reference internal temperature for cooling

The monthly internal set-point temperature for cooling averaged over space ϑ i,c,soll is specified in DIN V 18599-10. A permitted temperature of 2 K above the set-point temperature for heating is to be taken into account by including the utilization factor of the heat sources in the balance calculations, hence a value 2 K lower than the internal temperature for cooling shall be used for calculating the monthly balance:

ϑ i,c = ϑ i,c,soll – 2 K (36)

The daily operating time of the mechanical ventilation system in normal operation (i.e. on workdays) shall be taken into account when equation (83) is used to calculate the heat transfer coefficient for mechanical ventilation. Equation (36) remains unchanged when considering intermittent cooling operation.

Generally, ventilation and cooling systems are not operated at weekends or during holiday periods. As there is no energy need for cooling during these periods, no additional balance calculations with corresponding boundary conditions are needed.

6.1.3 Temperature of an adjacent unheated or uncooled zone

6.1.3.1 General

During heating operation, heat flows through adjacent unheated spaces shall either be taken into account by the thermal transmittance to the external environment (U-value) as specified in DIN EN ISO 6946, or the temperature of the unheated space is to be calculated. For heating, the temperature in an adjacent zone can be approximated assuming temperature correction factors according to 6.1.3.2. For cooling, the detailed calculation procedure described in 6.1.3.3 shall be used. The approximate method generally gives differences in temperature (i.e. between the heated and the unheated space) that are greater than those obtained using

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the detailed calculation. The simplified approach can also be used to calculate heat flows through surfaces in contact with the ground.

The evaluation report shall specify whether unheated spaces have been calculated by the approximate method using the U-value as specified in DIN EN ISO 6946, using generalized correction factors from Table 3 or using ϑu values obtained by detailed calculations according to 6.1.3.3.

6.1.3.2 Approximate method using temperature correction factors to determine the mean temperatures in unheated zones

In the approximate method, equation (37) shall be used to calculate the mean temperature in the unheated space (heating operation):

ϑ u = ϑ i – Fx (ϑ i – ϑ e) (37)

where

ϑ i is the reference internal temperature in the building zone (for heating: ϑ i,h, according to 6.1.1);

Fx is the temperature correction factor from Table 3.

The temperature ϑ u, calculated by equation (37), can be assumed to be the external temperature for all building element surfaces which do not border on external air or heated or cooled parts of the building. These include, for example, surfaces bordering on:

⎯ unheated basements;

⎯ non-habitable lofts;

⎯ residual roof spaces;

⎯ unheated sunspaces;

⎯ unheated attached staircases;

⎯ the ground.

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Table 3 —Temperature correction factors for various building elements

Line Heat flow outwards via Fx Temperature correction factor Fx f

1 External wall, window, ceiling to external air Fe 1,0

2 Roof (system boundary) FD 1,0

3 Ceiling to (non-habitable) loft) FD 0,8

4 Walls and ceilings to an apsis (jamb walls) Fu 0,8

5 Walls, floors and ceilings to unheated spaces (except basements)

Fu 0,5

Walls and windows to unheated sunspaces, these sunspaces having:

6 — single glazing; Fu 0,8

7 — double glazing; Fu 0,7

8 — thermal insulation glazing. Fu 0,5

B′a

< 5 m 5 m to 10 m > 10 m Elements forming the base of the buildingh

Rf or Rwb Rf or Rw

b Rf or Rwb

Surfaces of a heated basement bordering the ground: ≤ 1 > 1 ≤ 1 > 1 ≤ 1 > 1

9 — floor of a heated basement; FG 0,30 0,45 0,25 0,40 0,20 0,35

10 — wall of a heated basement. FG 0,40 0,60 0,40 0,60 0,40 0,60

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Table 3 (continued)

Line Heat flow outwards via Fx Temperature correction factor Fx f

Rf Rf Rf

≤ 1 > 1 ≤ 1 > 1 ≤ 1 > 1

Building or building zone without a basement

11 Floorc on ground without additional slab edge insulation but with insulation between floor bottom and ground

FG 0,45 0,6 0,4 0,5 0,25 0,35

Floorc on the ground, with slab edge insulationd:

12 — 5 m wide, horizontal FG 0,3 0,25 0,2

13 — 2 m deep, vertical FG 0,25 0,2 0,15

Basement ceiling and internal basement wall to unheated basement

14 — with perimeter insulationg FG 0,55 0,5 0,45

15 — without perimeter insulationg FG 0,7 0,65 0,55

16 Floor slab of spaces with low heatinge FG 0,2 0,55 0,15 0,5 0,1 0,35

17 Raised floor (e.g. ventilated crawlway) FG 0,9

a B′ = AG/(0,5 P) as in DIN EN ISO 13370, whereby AG is the area and P is the perimeter of the floor slab. b Rf: thermal resistance of the floor slab (applies to rows 9, 11, 16) or

Rw: thermal resistance of the basement wall (applies to row 10) or as an area-weighted average of Rf and Rw (applies to rows 9, 10).c In cases where there is ground-water flow, the temperature correction factors are increased by 15 %. d If the thermal resistance of the slab edge insulation is greater than 2 (m2 · K)/W and the floor slab is not insulated, also refer to

DIN EN ISO 13370:1998-12, Figure 2 and Figure 3. e For spaces with internal temperatures between 12 °C and 19 °C. f The values (except for those in rows 11 to 12) apply by analogy to surfaces of spaces with little heating. g The external insulation of basement walls in contact with the ground (perimeter insulation) from the top face of the floor slab with a

thermal resistance equal to or greater than 1,5 (m2 · K)/W and at least an equivalent insulation of the basement walls in contact with the external environment up to the point of contact with the façade insulation or top face of the floor above the basement.

h For simplification, a temperature correction factor FG = 0,7 may be assumed for all elements of the bottom of the building (cf. lines 9 to 16).

6.1.3.3 Detailed calculation of the temperature in an unheated or uncooled building zone

The mean temperature in an unheated or uncooled building zone shall be calculated as described in DIN EN ISO 13789, using the following equation:

V,ueT,ueV,iuT,iu

V,ueT,ueeV,iuT,iuiuu

)()(HHHH

HHHH+++

++++=

ϑϑΦϑ (38)

where

Φu is the heat flow (from heat sources) into the unheated or uncooled building zone (e.g. due to solar heat or internal heat sources); in the case of unheated or uncooled sunspaces this is the

DIN V 18599-2:2007-02

45

heat flow obtained from equation (115). Should there be heat sinks in such zones (e.g. heat flows through elements in contact with the ground calculated according to DIN EN ISO 13370) these shall also be taken into account, paying attention to the direction of the heat flows (i.e. by giving them the appropriate signs);

HT,iu is the transmission heat transfer coefficient of the elements between the considered zone and the adjacent unheated or uncooled building zone, calculated using equation (48);

HT,ue is the transmission heat transfer coefficient of the elements between the unheated or uncooled zone and the external environment; it corresponds to HT,D as calculated using equation (44) or equation (45) or HT,s as in 6.2.4 or DIN EN ISO 13789;

HV,iu is the ventilation heat transfer coefficient between the considered zone and the adjacent unheated or uncooled building zone, calculated using equation (95) (HV,iu = 0 can generally be assumed);

HV,ue is the ventilation heat transfer coefficient between the adjacent unheated or uncooled zone and the external environment, calculated using equation (94);

Elements of the wall between the heated or cooled and unheated or uncooled zones shall be treated as internal elements (see also 6.2.2).

If the unheated or uncooled zone is adjacent to several other zones, equation (38) may be extended accordingly by adding together the weighted temperatures or heat transfer coefficients of all adjacent building zones and of the section forming the boundary with the external environment:

∑

∑+

++

=

jjj

jjjj

HH

HH

)(

)(

iV,iT,

iV,iT,i,u

u

ϑΦ

ϑ (39)

Heat flows from and into adjacent uncooled zones shall not be taken into account if the adjacent uncooled zone meets the requirements for thermal protection in summer according to DIN 4108-2. In all other cases, the mean temperature in the adjacent uncooled zone shall be determined using equation (38) or equation (39).

6.1.4 Temperature of an adjacent heated or cooled zone

Heat flows from or to adjacent heated or cooled zones shall only be taken into account if the internal set-point temperatures of the two zones differ by more than 4 K.

When considering heating, the temperature of the adjacent zone ϑz shall be the reference internal temperature for heating; when considering cooling, ϑz shall be the reference internal temperatuare for cooling.

ϑz = ϑ i,h,z in the balance of the energy need for heating (40)

ϑz = ϑ i,c,z in the balance of the energy need for cooling (41)

where

ϑ i,h,z is the reference internal temperature of the adjacent building zone for heating according to 6.1.1;

ϑ i,c,z is the reference internal temperature of the adjacent building zone for cooling according to 6.1.2.

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46

6.2 Transmission heat sinks/heat sources

6.2.1 Direct transmission to the external environment

6.2.1.1 Calculation of the heat sinks and sources due to transmission to the external environment

Transmission heat sinks and sources represented by building elements forming the boundary between the building zone and the external environment shall be calculated using the following equations:

QT,e = HT,D (ϑi – ϑe) t for ϑ i > ϑe (heat sink) (42)

and

QT,e = HT,D (ϑe – ϑi) t for ϑe < ϑi (heat source) (43)

where

HT,D is the transmission heat transfer coefficient between the heated or cooled building zone and the external environment;

ϑ i is the reference internal temperature ϑ i,h in the building zone for heating according to 6.1.1, or the reference internal temperature ϑ i,c in the building zone for cooling according to 6.1.2, respectively;

ϑe is the average external temperature for the respective month;


The heat transfer coefficient HT,D shall include the area-related thermal transmittance of the elements between the building zone and external environment as well as thermal bridges to the external environment. The transmission heat transfer coefficient shall be calculated as described in DIN EN ISO 13789:2005-06 (with HT,D corresponding to HD), or if a simplified method is preferred, using equation (44) or equation (45).

6.2.1.2 Calculation of coefficients of heat transfer to the external environment (assuming a standard allowance for thermal bridges)

The transmission heat transfer coefficient is the sum of the coefficients of the individual building elements forming the boundary between the building zone and the external environment. A standard allowance can be used to take into account the effect of thermal bridges ΔUWB. The transmission heat transfer coefficient is thus calculated as follows:

HT,D = Σ (Uj Aj) + ΔUWB Σ Aj (44)

where

Aj is the area of element j which forms part of the boundary between the building zone and the external environment. The dimensions of windows and doors shall be the clear internal unfinished dimensions of their openings;

Uj is the thermal transmittance of element j of the building envelope, calculated according to DIN EN ISO 6946 for opaque elements, or according to DIN V 4108-4 for transparent elements;

ΔUWB is the standard allowance for thermal bridges in external surfaces;

j is the element.

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47

The standard allowance for thermal bridges shall take certain types of thermal bridges into account, such as:

⎯ edges and corners of buildings;

⎯ (perimeter) reveals at windows and doors;

⎯ wall/floor junctions;

⎯ floor supports;

⎯ balcony and porch slabs with thermal breaks.

Where no calculations are available, ΔUWB = 0,10 W/(m2 · K) shall be assumed; for external building elements with internal insulation layers and a connecting solid floor, ΔUWB = 0,15 W/(m2 · K) shall be assumed. If its equivalence is checked and verified according to DIN 4108 Supplement 2, a value of ΔUWB = 0,05 W/(m2 · K) can be used.

If, when using equation (44), external building elements are included for which the effect of thermal bridges is already accounted for in the value of Uj (e.g. thermal transmittance of curtain walling calculated as described

in DIN EN 13497), the allowance for thermal bridges in the thermal envelope area ΣAj in equation (44) can be reduced by the surface areas of the corresponding building elements.

6.2.1.3 Calculation of coefficients of heat transfer to the external environment (using linear thermal transmittance)

In building zones with good thermal insulation, heat transfer via thermal bridges can be relatively extensive in relation to the total transmission heat flow, and an assumed default value shall not be used to calculate the effect of these in such cases. The heat transfer coefficient HD shall be calculated as in equation (45), taking into account the linear thermal transmittance:

HT,D = Σ (Uj Aj) + Σ (lj Ψj) (45)

where

lj is the length of the two-dimensional thermal bridge j;

Ψj is the linear thermal transmittance of thermal bridge j, calculated according to DIN EN ISO 10211-1 and using the boundary conditions described in DIN 4108 Supplement 2;

j is a building element or a two-dimensional thermal bridge.

Values of linear thermal transmittance Ψ (thermal bridge loss coefficients) can be found in thermal bridge catalogues or calculated as described in DIN EN ISO 10211-1 using suitable multi-dimensional calculation methods. In such cases, theΨ values corresponding to the dimensions used (external or internal length of two-dimensional thermal bridges) shall be taken into consideration accordingly.

6.2.2 Transmission through unheated or uncooled spaces to the external environment

Transmission heat sinks and sources to the external environment due to transmission through unheated or uncooled spaces (e.g. lofts and residual roof spaces, basements or small attached garages or storerooms) can be calculated in the same way as direct transmission heat sources and sinks using equations (42) and (43), respectively, if the U-value according to DIN EN ISO 6946 has already taken the unheated or uncooled space into account.

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48

An alternative method is to use equations (46) and (47) to calculate transmission into the unheated or uncooled space as a function of the internal temperature of this space, in which case the U-values between the building zone and the unheated or uncooled space are to be used. The temperature of the unheated or uncooled space shall be calculated as described in 6.1.3.

QT,u = HT,iu (ϑ i – ϑ u) t for ϑ i > ϑ u (heat sink) (46)

and

QT,u = HT,iu (ϑ u – ϑ i) t for ϑ i < ϑ u (heat source) (47)

where

HT,iu is the transmission heat transfer coefficient between the heated and unheated building zones or between cooled and uncooled building zones, obtained from equation (48) or DIN EN ISO 13789 (corresponding to HD);

ϑ i is the reference internal temperature ϑ i,h of the building zone for heating according to 6.1.1 or the reference internal temperature ϑ i,c for cooling according to 6.1.2, respectively;

ϑu is the mean temperature of the unheated or uncooled building zone, determined either approximately using equation (37) (for heating mode), or in detail using equation (38);

t is the calculation period (t = 24 h).

The transmission heat transfer coefficient into the unheated or uncooled zone shall be calculated using equation (48).

HT,iu = ∑j

jj AU (48)

where

Aj is the area of a building element j between the considered building zone and the unheated or uncooled space;

Uj is the thermal transmittance of element j when this is an internal element (calculated according to DIN EN ISO 6946 for opaque elements but without taking into account thermal resistance through unheated spaces, or according to DIN V 4108-4 for glazed elements).

Thermal bridges are generally to be taken into account by analogy with 6.2.1.2 and 6.2.1.3.

If the U-value of the element for thermal transmittance to the external environment is known, it can be converted to the U-value for internal applications of the element using equation (49). This applies especially to glazing.

sise.comp external

.comp internal 11

RRU

U+−

= (49)

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49

where

Rse is the external surface resistance of the element according to DIN EN ISO 6946 or DIN EN ISO 10077-1 (generally 0,04 (K · m2)/W);

Rsi is the internal surface resistance of the element according to DIN EN ISO 6946 or DIN EN ISO 10077-1 (generally 0,13 (K · m2)/W for vertically aligned elements).

NOTE The transmission heat transfer coefficient HT,iu used here is not identical to the heat transfer coefficient through unheated spaces HU as specified in DIN EN ISO 13789, since DIN V 18599-2 deals with transmission to the unheated or uncooled space, whereas DIN EN ISO 13789 deals with transmission to the external environment. The latter is calculated in the same way as HD, but omitting a correction factor b.

6.2.3 Transmission to adjacent heated or cooled building zones

Transmission heat sinks and sources represented by building components forming the boundary between the building zone and adjacent zones with different internal temperatures need to be taken into account only if the internal set-point temperatures differ by more than 4 K.

QT,z = HT,iz (ϑ i – ϑz) t for ϑ i > ϑz (heat sink) (50)

and

QT,z = HT,iz (ϑz – ϑ i) t for ϑ i < ϑz (heat source) (51)

where

HT,iz is the transmission heat transfer coefficient between the considered building zone i and the adjacent building zones z, obtained from equation (52) or from DIN EN ISO 13789 (corresponding to HD);

ϑi is the reference internal temperature ϑ i,h in the building zone for heating according to 6.1.1 or the reference internal temperature ϑ i,c for cooling according to 6.1.2, respectively;

ϑz is the reference internal temperature of the adjacent building zone according to 6.1.4;


The heat transfer coefficient shall be obtained from equation (52) or from DIN EN ISO 13789, using the summated values of the areas between the individual building zones. The temperature for the adjacent building zone is the mean temperature over the calculation period.

HT,iz = ∑j

jj AU (52)

where

Aj is the area of a building element j between the building zones;

Uj is the thermal transmittance of element j when used as an internal element (calculated according to DIN EN ISO 6946 for opaque elements, or according to DIN V 4108-4 for glazed elements).

Thermal bridges can generally be ignored.

DIN V 18599-2:2007-02

50

If the U-value of the element for thermal transmittance to the external environment is known, it can be converted to the U-value for internal elements using equation (49). This particularly applies to glazing.

6.2.4 Transmission through the ground

In building zones which are only heated, the transmission heat sinks or sources through the ground or a basement shall be as for transmission through unheated spaces according to 6.2.2 using the simplified approach with temperature correction factors determined according to equation (37), (see Table 3 for these temperature correction factors).

In other cases, the transmission heat sinks or sources through the ground shall be calculated using equations (53) or (54), or where applicable, using equation (55).

QT,s = HT,s (ϑ i – ϑe) t for ϑ i > ϑe (heat sink) (53)

and

QT,s = HT,s (ϑe – ϑi) t for ϑ i < ϑe (heat source) (54)

where

HT,s is the coefficient for heat transfer through the ground (with HT,s corresponding to Ls from DIN EN ISO 13370);

ϑ i is the reference internal temperature ϑ i,h of the building zone for heating according to 6.1.1 or the reference internal temperature ϑ i,c for cooling according to 6.1.2;

ϑe is the mean monthly external temperature;


The transfer coefficient relating to heat flows through the ground shall be calculated from the steady-state thermal coupling coefficient Ls using the method described in DIN EN ISO 13370. In the absence of information on the characteristics of the ground, its thermal conductivity can be assumed to be 2,0 W/(m · K).

In building zones with considerable heat losses through the ground, the steady-state thermal transfer coefficient from DIN EN ISO 13370 can lead to an overestimation of the monthly heat losses through the ground in the winter. If loss of heat via the ground constitutes a large part of the total heat sinks, the efficacy of calculating heat flows through the ground in detail as described in DIN EN ISO 13370:1998-12, B.1 shall be considered. In this case, the monthly total heat flow calculated using equation (55) shall be stated.

QT,s = Φm t (55)

where

Φm is the mean daily heat flow through the ground in the respective month, calculated as described in DIN EN ISO 13370:1998-12, Annex B;

t is the calculation period (t =24 h).

6.3 Ventilation heat sinks/sources

6.3.1 Infiltration

Heat sources and sinks due to infiltration shall be calculated using equation (56) and (57).

QV,inf = HV,inf (ϑi – ϑe) t for ϑi > ϑe (heat sink) (56)

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51

and

QV,inf = HV,inf (ϑe – ϑi) t for ϑi < ϑe (heat source) (57)

where

HV,inf is the infiltration heat transfer coefficient;

ϑ i is the reference internal temperature ϑ i,h in the building zone for heating according to 6.1.1 or the reference internal temperature ϑ i,c for cooling according to 6.1.2;



The infiltration heat transfer coefficient shall be calculated as follows:

HV,inf = ninf V cp,a ρa (58)

where

ninf is the daily mean infiltration air change rate, calculated using equation (59) or (60) respectively;

V is the net volume of the space;

cp,a is the specific heat capacity of air;

ρa is the density of air.

cp,a ρa shall be assigned a value of 0,34 Wh/(m3 ⋅ K).

For interior building zones (i.e. which have no surfaces bordering on the external environment), external air infiltration shall be zero.

6.3.1.1 Determination of the infiltration air change rate

The infiltration air change rate is a daily mean value calculated on the basis of the airtightness of the building. The airtightness of the building is given in relation to the measured air change rate at a pressure difference of 50 Pa (n50-value). Default values are specified for buildings which have not been tested.

If mechanical ventilation without a balanced supply air and extract air volume flow is used, the infiltration will increase or decrease in relation to the pressure difference brought about by the ventilation system.

⎯ Where no mechanical ventilation is used (because either no system is installed or the ventilation system is switched off at weekends or during holiday periods), equation (59) shall be used to determine the mean daily infiltration air change rate:

n inf = n50 ewind (59)

⎯ Mechanical ventilation increases or reduces the mean daily infiltration air change rate as expressed by equation (60):

ninf = n50 ewind ⎟⎟⎠

⎞⎜⎜⎝

⎛+

h 241 V,mech

V,mecht

f (60)

DIN V 18599-2:2007-02

52

where

n50 is the air change rate at a pressure difference of 50 Pa

— if an airtightness test has been carried out, the measured value shall be used;

— if no test has been carried out and there is no test planned, a default value from Table 4 shall be used;

ewind is the wind shielding coefficient; a default value of ewind = 0,07 may be assumed (corresponding to the shielding coefficient in DIN EN ISO 13790 for moderate shielding of buildings with more than one façade exposed to wind);

tV,mech is the daily operating time of the ventilation system (see DIN V 18599-10);

fV,mech is a factor taking into account an increase or decrease in infiltration due to mechanical ventilation in equations (61) to (63).

Table 4 — n50 design values (default values for untested buildings)

Categories for general assessment of the airtightness of a building

Design values n50

h–1

I a) 2; b) 1

II 4

III 6

IV 10

Airtightness categories for building zones are given in Table 4:

⎯ Category 1: conforming to the airtightness requirements for buildings in DIN 4108-7:2001-08, 4.4 (i.e. airtightness tests are carried out after building work has been completed);

a) buildings without HVAC systems (requirements for airtightness of building: n50 ≤ 3 h–1),

b) buildings with HVAC systems (also applies to ventilation systems of residential spaces) (requirements for airtightness of building: n50 ≤ 1,5 h–1);

⎯ Category II: buildings or parts of buildings yet to be completed and for which no airtightness tests are planned;

⎯ Category III: all cases not included in categories I, II or IV;

⎯ Category IV: apparent leaks such as open gaps in the infiltration protection layer of the thermal envelope.

An airtightness test shall be carried out to determine the n50-value if it is not certain to which category a building or zone is to be assigned.

6.3.1.2 Evaluation of infiltration of zones with mechanical ventilation systems

⎯ For mechanical ventilation systems with balanced supply air/extract air flows,

DIN V 18599-2:2007-02

53

fV,mech = 0 (61)

⎯ For ventilation systems with mechanical supply air feed and possibly with mechanical air extraction, where nZUL > nABL,

1

1

12

50

ABLZUL

wind

windV,mech −

⎟⎟⎠

⎞⎜⎜⎝

⎛ −+

=

nnn

ef

f (62)

⎯ For ventilation systems with mechanical air extraction and possibly with mechanical supply air feed, where nABL > nZUL,

2

50

ABLZUL

wind

windV,mech

1

11

⎟⎟⎠

⎞⎜⎜⎝

⎛ −+

−=

nnn

ef

f (63)

where

ewind, fwind is the wind shielding coefficient; default values of ewind = 0,07 and fwind = 15 may be assumed, (corresponding to the shielding coefficient as given in DIN EN ISO 13790 for moderate shielding of buildings with more than one façade exposed to wind);

nZUL is the sum of the supply air changes due to mechanical ventilation nmech,ZUL obtained from equations (87) or (88) and due to air transferred from adjacent building zones nz,ZUL obtained from equation (101);

nABL is the sum of the extract air changes due to mechanical ventilation nmech,ABL obtained from equation (89) and due to the air drawn in from adjacent building zones, nz,ABL obtained from equation (103);

For ventilation systems in residential buildings, a value of fv,mech = 0 shall be used as a default value.

6.3.2 Window airing

Heat sinks and heat sources due to ventilation by opening doors and windows shall be calculated as follows:

QV,win = HV,win (ϑi – ϑe) t for ϑ i > ϑe (heat sink) (64)

and

QV,win = HV,win (ϑe – ϑi) t for ϑ i > ϑe (heat source) (65)

where

HV,win is the heat transfer coefficient of window airing;




DIN V 18599-2:2007-02

54

HV,win is calculated as follows:

HV,win = nwin V cp,a ρa (66)

where

nwin is the mean daily air change rate due to window airing as calculated using equation (67), (71) or (72);




cp,a ρa shall be given a value of 0,34 Wh/(m3 · K).

6.3.2.1 Determination of air change rate due to window airing

All air change flows through windows, doors and other openings to the outside, including external inlet vents for ventilation systems, shall be included in the calculations of the air change rate due to window airing. The air change rate due to window airing shall be determined as a mean daily value depending on the external air change necessitated by the given usage of the zone or building. Reductions in the air change rate due to window airing as a function of infiltration shall be taken into consideration.

Where mechanical ventilation systems supply air to a building zone, the air change rate brought about by the ventilation system shall be subtracted from the air change rate theoretically required from window airing. However, in the case of natural ventilation of zones which have mechanical ventilation systems in which the extract air flow is greater than the supply air flow, it may be necessary to increase the air change rate due to window airing up to a level where the extract air flow is balanced by a combination of window airing, infiltration and supply air from the ventilation system.

If a ventilation system in an adjacent zone extracts air from the considered zone, then the respective volume flow shall also be considered to be extract air volume flow as described in 6.3.5 when determining the air change rate due to window airing.

Whenever the building zone has openings to the outside, a minimum value of 0,1 h–1 shall be assumed for window airing, irrespective of the contributions made to air change by infiltration and mechanical ventilation. Window airing is negligible for all building zones which have no openings to the external environment.

⎯ Where no mechanical ventilation is used (because either no system is installed, or the ventilation system is switched off at weekends or during holiday periods), equation (67) shall be used to determine the mean daily air change rate due to window airing:

nwin = 0,1 h–1 + Δnwin h 24

nutzt (67)

In the above, the following applies:

— for nnutz < 1,2 h–1 and (nnutz – (nnutz – 0,2 h–1)/h–1 ninf – 0,1 h–1) > 0 h–1

Δnwin = nnutz – (nnutz – 0,2 h–1)/h–1 ninf – 0,1 h–1 (68)

— for nnutz ≥ 1,2 h–1 and (nnutz – ninf – 0,1 h–1) > 0 h–1

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55

Δnwin = nnutz – ninf – 0,1 h–1 (69)

In all other cases:

Δnwin = 0 h–1 (70)

where

nnutz is the usage-dependent minimum air change rate, calculated using equation (80);

ninf is the air change rate due to infiltration, calculated using equation (59);

tnutz is the daily usage time according to DIN V 18599-10.

⎯ If a mechanical ventilation system is used, the mean daily air change due to window airing shall be determined by applying equation (71), provided that the usage time does not exceed the operating time of the ventilation system (standard case: tV,mech = tnutz):

nwin = 0,1 h–1 + Δnwin,mech h24

mechV,t (71)

⎯ If a mechanical ventilation system is used which is not operated over the entire period in which the zone is used, the mean daily air change rate due to window airing shall be determined by applying equation (72), (exception: tV,mech < tnutz):

nwin = 0,1 h–1 + Δnwin h 24

mechV,nutz tt − + Δnwin,mech

h 24mechV,t

(72)

where

Δnwin is the additional air change rate due to window airing during the times when the building is in use but the mechanical ventilation system is not in operation, calculated using equations (68) and (69);

Δnwin,mech is the additional air change rate due to window airing during the times when the mechanical ventilation system is in operation, calculated using equations (76) and (79);

tnutz is the daily usage time as specified in DIN V 18599-10:

tV,mech is the daily operating time of the ventilation system as specified in DIN V 18599-10.

⎯ If a mechanical ventilation system is operated in an adjacent zone, the air change due to air transfer from that zone shall be taken into account as described in 6.3.5. Equations (71) and (72) shall apply accordingly.

A distinction shall be made between the following cases when determining the additional air change rate Δnwin,mech:

a) If the usage-dependent minimum air change rate is covered by supply air from the mechanical ventilation system and partially by infiltration, and:

1) no additional air flow is required to balance the extract air volume flow;

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56

2) the extract air volume flow exceeds the inflow due to supply air and infiltration. In this case additional air inflow (e.g. through vents in the building envelope) is required.

b) If the usage-dependent minimum air change rate is not covered by supply air from the mechanical ventilation system and by infiltration, or there is no supply air system and:

1) the required supply of fresh air is supplemented by window airing; no additional air flow is required to balance the extract air volume flow;

2) the extract air volume flow exceeds the usage-dependent air change rate; in this case additional air inflow (e.g. through vents in the building envelope) is required.

Giving due consideration to infiltration, the additional usage-dependent air change rate Δnwin,mech,0 that is required shall be calculated as follows:

— for nnutz < 1,2 h–1 and [nnutz – (nnutz – 0,2 h–1)/h–1 ⋅ n50 ⋅ ewind ⋅ (1 + fV,mech) – 0,1 h–1] > 0 h–1:

Δnwin,mech,0 = nnutz – (nnutz – 0,2 h–1)/h–1 ⋅ n50 ⋅ ewind ⋅ (1 + fV,mech) – 0,1 h–1 (73)

— for nnutz ≥ 1,2 h–1 and [nnutz – n50 ⋅ ewind ⋅ (1 + fV,mech) – 0,1 h–1] > 0 h–1:

Δnwin,mech,0 = nnutz – n50 ⋅ ewind ⋅ (1 + fV,mech) – 0,1 h–1 (74)

In all other cases:

Δnwin,mech,0 = 0 h–1 (75)

Thus, taking the different cases into consideration, the additional air change due to window airing Δnwin,mech that is required shall be determined as follows.

Case a) The usage-dependent air change rate is achieved completely by the supply air flow:

Condition: Δnwin,mech,0 ≤ nZUL

Case a-1) Condition: nABL ≤ (nZUL + n50 ewind):

Δnwin,mech = 0 h–1 (76)

Case a-2) Condition: nABL > (nZUL + n50 ewind):

Δnwin,mech = nABL – nZUL –n50 ewind (77)

Case b) The usage-dependent air change rate is not achieved completely by the supply air flow:

Condition: Δnwin,mech,0 > nZUL

Case b-1) Condition: nABL ≤ (nwin,mech,0 + n50 ewind):

nwin,mech = nwin,mech,0 – nZUL (78)

Case b-2) Condition: nABL > (Δnwin,mech,0 + n50 ewind):

Δnwin,mech = nABL – nZUL – n50 ewind (79)

DIN V 18599-2:2007-02

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where

nnutz is the usage-dependent minimum air change rate according to DIN V 18599-10, obtained by means of equation (80);

n50 is the air change rate at a pressure difference of 50 Pa

— when an airtightness test has been carried out, the measured value shall be used;

— if no test has been carried out and there is no test planned, a default value from Table 4 shall be used;

ewind is the wind shielding coefficient; a default value of ewind = 0,07 may be assumed (corresponding to the shielding coefficient from DIN EN ISO 13790 for moderate shielding of buildings with more than one façade exposed to wind);

fV,mech is the evaluation factor for infiltration when a mechanical ventilation system is in operation, calculated using equations (61) to (63);

nZUL is the sum of the supply air changes due to mechanical ventilation nmech,ZUL, obtained by means of equations (87) or (88) and due to the transfer of air from adjacent building zones, nz,ZUL (see equation (101));

nABL is the sum of the extract air changes due to mechanical ventilation nmech,ABL, obtained by means of equation (89) and due to the air drawn in from adjacent building zones, nz,ABL, (see equation (103));

6.3.2.2 Usage-dependent minimum air exchange with external air

The minimum volume flow of external air into the building zone is specified in DIN V 18599-10 as a function of the usage of the building or zone. The air change rate shall be calculated using equation (80). The usage-dependent minimum air exchange with external air shall be provided by window airing and/or mechanical ventilation.

nnutz = VAV BA

& (80)

where

V⋅A is the minimum external air volume flow per unit area according to DIN V 18599-10, in m3/(hm2);

AB is the reference area of the building zone, in m²;

V is the net volume of the space, in m³.

The usage-dependent minimum air change rate with outdoor air nnutz is given in DIN V 18599-10 for residential buildings. This value shall be adjusted to take into account the occupancy of the building zone if the minimum external air volume flow related to the number of persons and a detailed usage profile as in DIN V 18599-10 is used.

6.3.3 Mechanical ventilation

When calculating the heat and cold gains due to mechanical ventilation by means of equations (81) and (82), the temperature of the supply air vented directly into the building zone by terminal devices is used in the evaluations. Depending on the ventilation concept, any additional air exchange between adjacent building

DIN V 18599-2:2007-02

58

zones which is due to mechanical ventilation shall also be taken into consideration (see 6.3.5, equations (97) to (103)).

QV,mech = HV,mech (ϑi – ϑV,mech) t for ϑi > ϑV,mech (heat sink) (81)

and

QV,mech = HV,mech (ϑV,mech – ϑi) t for ϑi < ϑV,mech (heat source) (82)

where

HV,mech is the heat transfer coefficient of mechanical ventilation calculated using equation (83);


ϑV,mech is the mean supply air temperature calculated using equations (90) to (93);


Heat sources and heat sinks due to HVAC systems shall be taken into consideration in the building zone if they occur independently of the current heat or cooling load. This applies, for example, to ventilation systems for residential buildings and to ventilation systems with central air handling. Air-heating systems are usually specifically designed to meet the heating requirement of the building zone and are not taken into account here.

The heat transfer coefficient of the supply air of the ventilation system shall be calculated as follows:

HV,mech = nmech V cp,a ρa (83)

where

nmech is the mean daily air change rate due to mechanical ventilation, obtained by means of equation (84);



ρa is the density of air;


6.3.3.1 Determination of the mean air change rate due to ventilation systems

The air change rate due to ventilation systems shall be determined as the mean daily value of the supply air transported into the building zone by the ventilation system in relation to the volume of air which can be replaced in the zone. Where necessary, the value for the minimum external air volume flow given in DIN V 18599-10 shall be increased in relation to the minimum requirements of the system (see Annex E for explanatory notes) or, for constant air volume systems which are designed to meet the entire cooling load, it shall be increased in relation to the maximum cooling load as specified in Annex C. In the case of variable air volume systems dependent on the cooling load, the minimum volume flow shall be assumed. Default values are available for residential ventilation systems and systems which meet only part of the total external air change requirements.

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The mean daily air change rate due to a ventilation system shall be calculated using equation (84):

nmech = nmech,ZUL h 24

mechV,t (84)

where

nmech,ZUL is the air change rate due to supply air when the ventilation system is in operation, calculated using equations (85) to (88);


NOTE For extraction-only ventilation systems, nmech = nmech,ZUL = 0 h–1. In these cases, the extract air volume flow is used directly for calculating the energy required by the fans as described in DIN V 18599-3, where appropriate, heat recovery, and, where relevant, in calculations described in DIN V 18599-5 (e.g. heat pumps for space heating) and DIN V 18599-8 (e.g. heat pumps for the domestic hot water supply). The inflow air required to balance the air extracted by the ventilation system is taken into account in the air change rate values from window airing.

6.3.3.2 Air change due to supply air from mechanical ventilation systems

⎯ The supply air change rate as specified in DIN V 18599-10 shall be used in the calculations for ventilation systems for residential buildings. Provisions in DIN V 18599-6 shall also be observed where applicable.

nmech,ZUL = nmech (see DIN V 18599-10) (85)

This also applies to other ventilation systems which only provide part of the required minimum air exchange with external air where no detailed information on the systems is available.

⎯ In the case of ventilation systems which meet the entire ventilation requirements, the minimum volume flow required by the system as well as the minimum external air change necessitated by the type of usage shall be maintained. Where constant air volume systems are designed to meet the entire cooling requirement of the building zone, the required minimum volume flow shall be determined in relation to the maximum cooling load of the building zone (see also DIN V 18599-3):

( )V,mechiapa

c,maxmech,b ϑϑ −

=Pc

QV

&& (86)

The air change rate shall be determined using the volume flow and the net volume of the building zone:

VV

n bmech,ZULmech,

&= (87)

where

V⋅mech,b is the greatest individual value of the following parameters: the usage-dependent minimum volume flow given in DIN V 18599-10, the minimum volume flow required by the system (a design value; see Annex E for default values), and (for ventilation systems designed to meet the entire cooling load) the volume flow obtained from equation (86);


Q⋅c,max is the maximum cooling load, calculated using equation (C.1);

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ϑ i the internal set-point temperature of the building zone for cooling ϑi,c,soll from DIN V 18599-10;

ϑV,mech is the minimum supply air temperature calculated using equations (90) to (93);



cp,a ρa shall be assigned a value of 0,34 Wh/(m3 · K).

⎯ For systems providing supply air only, the air transferred into adjacent zones shall be treated as inflowing air (supply air) from other zones (see 6.3.5).

⎯ For extraction-only ventilation systems

nmech,ZUL = 0 (88)

The extract air volume flow shall be balanced by infiltration, window airing and, in some cases, by air from adjacent zones.

6.3.3.3 Extract air change due to mechanical ventilation systems

Where no known values are available, the extract air volume flow of HVAC systems shall be specified in the design phase (see Annex E for default values). The following equation is used to calculate the air change rate:

nmech,ABL = V

VABL&

(89)

Where no actual data are available, nmech,ABL = nmech,ZUL shall be assumed; or for extraction-only systems, nmech,ABL = nnutz.

For extraction-only ventilation systems in residential buildings, the default value specified in DIN V 18599-10 applies; provisions in DIN V 18599-6 may also need to be observed: nmech,ABL = nmech (see DIN V 18599-10).

The extract air volume flow shall be balanced by mechanical air supply, infiltration, window airing and, in some cases, by air from the adjacent zones.

6.3.3.4 Supply air temperature of mechanical ventilation

⎯ The supply air temperatures from DIN V 18599-3 or the following general expression shall apply to ventilation systems without air handling:

ϑV,mech = ϑe (90)

⎯ The supply air temperatures from DIN V 18599-3 or the following general expression shall apply to simple ventilation systems with uncontrolled heat exchangers and where the extract air temperature is equal to the internal air temperature:

ϑV,mech = ϑe + ηV,mech ⋅ (ϑi – ϑe) (91)

⎯ The supply air temperatures from DIN V 18599-6 shall be used in the calculations for ventilation systems of residential buildings:

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ϑV,mech = ϑV,mech,WLA (92)

⎯ For ventilation systems with temperature-controlled air handling, supply air temperatures shall be as specified in DIN V 18599-7; for systems without cooling functions, they shall be as specified in DIN V 18599-3.

ϑV,mech = ϑV,mech,RLT (93)

where

ϑe is the average monthly external temperature;

ηV,mech is the efficiency of heat recovery by the extract air/supply air heat exchanger;

ϑi is the reference internal temperature ϑ i,h of the building zone for heating according to 6.1.1 or the reference internal temperature ϑ i,c for cooling according to 6.1.2;

ϑV,mech,WLA is the supply air temperature to be assumed, according to DIN V 18599-6, for residential building ventilation systems with extract air/supply air heat exchangers;

ϑV,mech,RLT is the supply air temperature specific to the system, as specified in DIN V 18599-3 or DIN V 18599-7.

6.3.3.5 Note on the evaluation of ventilation systems with extract air/supply air heat exchangers for use in residential buildings

In order to be able to specify the usable heat of heat recovery by extract air/supply air heat exchangers in the energy balance of the building zone, required for evaluating the performance of a residential building's ventilation system according to DIN V 18599-6, the energy balance of such ventilation systems shall be calculated twice:

a) with heat recovery using the extract air/supply air heat exchanger, by equation (92), and

b) without heat recovery, by equation (90).

The difference between the results of the balance of the energy need for heating (and, where applicable, that of the energy need for cooling) for case b) and case a) corresponds to the usable heat recovered by heat exchange from extract air to supply air.

6.3.4 Ventilation in unheated or uncooled building zones

The rate of air change of adjacent unheated or uncooled building zones to the external environment shall be taken into account when calculating the temperature in such zones (see equation (38)).

The ventilation heat transfer coefficient of adjacent unheated or uncooled building zones (e. g, sunspaces) to the external environment shall be calculated as follows:

HV,ue = cp,a ρa nue Vu (94)

The ventilation heat transfer coefficient of adjacent unheated or uncooled building zones to the zone being evaluated shall be assumed to be as follows:

HV,iu = 0 (95)

where

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nue is the air change between the adjacent unheated or uncooled building zone and the external environment, calculated using equation (96):

Vu is the net volume of the unheated or uncooled building zone;




The following default value shall be used for the air change rate between an adjacent unheated or uncooled zone and the external environment:

nue = 0,6 h–1 (96)

If the temperature in the unheated or uncooled space ϑu rises above 20 °C when the air change rate nue is 0,6 h–1, then the air change rate (daily mean value) can be increased up to a maximum of 2 h–1 in order to prevent overheating in summer (cooling applications).

where

ϑu is the temperature in the unheated or uncooled space calculated using equation (38)

6.3.5 Air exchange between building zones

Where there is a high rate of air exchange between different spaces or enclosures in a building, these shall be grouped together into a single building zone.

If, in exceptional cases, there are two zones with exchange of air between the zones, the resulting heat sources and sinks shall be calculated using equations (97) and (98), respectively. Planned air changes exist, for example, where mechanical ventilation systems are designed to serve more than one zone. The air volume flows shall be specified so as to ensure a balance between the volume of incoming and outgoing air and an adequate supply of fresh air to the individual zones.

When no mechanical ventilation system is installed, the air exchange between building zones need only be taken into consideration if the internal set-point temperatures differ by more than 4 K.

The balance of air flowing into each zone shall be calculated. In the calculations for the adjacent zone, the volume flow is treated as extract air flow.

The following equation shall be used to calculate the heat of the air flowing into a zone:

QV,z = HV,z (ϑ i – ϑz) t for ϑ i > ϑz (heat sink) (97)

and

QV,z = HV,z (ϑz – ϑ i) t for ϑ i < ϑz (heat source) (98)

where

HV,z is the ventilation heat transfer coefficient;

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ϑz is the average temperature (reference internal temperature) of the zone from which the air is coming;


The heat transfer coefficient of air change shall be calculated using the following equation:

HV,z = V⋅z,d cp,a ρa (99)

where

V⋅z,d is the mean volume flow from the adjacent zone over a day;




Equation (100) shall be used to calculate the mean daily volume flow of air transferred from an adjacent zone due to a mechanical ventilation system.

h24V,mech

zdZ,t

VV && = (100)

where

ZV& is the volume flow of air from an adjacent zone when the mechanical ventilation system is in operation;


6.3.5.1 Supply air change rate from adjacent building zones

When using equations (76) to (79) to calculate the air change rate due to window airing, the amount of supply air coming from an adjacent zone shall also be taken into consideration.

VV

n ZZULz,

&= (101)

where

ZV& is the volume flow of air from an adjacent zone (in the case of mechanical ventilation systems, only when these are in operation);

NOTE ZV& shall be taken into account when determining nz,ABL of the adjacent zone.

V is the net volume of the building zone being evaluated.

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For building zones without windows or wall openings to the outside and with greater extract air volume flows:

nz,ZUL = nmech,ABL – nmech,ZUL (102)

where

nmech,ABL is the extract air change rate of the mechanical ventilation system within the building zone being evaluated (see 6.3.3.3);

nmech,ZUL is the supply air change rate of the mechanical ventilation system within the building zone being evaluated (see 6.3.3.2).

In all other cases, the supply air change rate shall be specified taking into account structural and technical aspects of the ventilation.

6.3.5.2 Extract air change rate into adjacent zones

To calculate the air change rate due to window airing, the amount of supply air flowing into an adjacent building zone shall also be taken into consideration:

VVn Z

ABLz,&

= (103)

where

ZV& is the volume flow of air into an adjacent zone (in the case of mechanical ventilation systems, only

when these are in operation); ZV& shall be taken into account when determining nz,ZUL of the adjacent zone;

V is the net volume of the building zone being evaluated.

When air is drawn into building zones without windows or wall openings to the outside, the extract air volume flows into the zone can be calculated using the following equation:

( )i

jjj

i VVnn

VV

n ZUL,mech,ABL,mech,ZABLz,

−==&

(104)

where

nmech,ABL,,j is the extract air change rate of the mechanical ventilation system within the adjacent building zone;

nmech,ZUL,,j is the supply air change rate of the mechanical ventilation system within the adjacent building zone;

Vj is the net volume of the adjacent building zone;

Vi is the net volume of the building zone being evaluated.

In all other cases, the extract air change rate shall be specified taking into account structural and technical aspects of the ventilation.

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6.4 Radiation heat sources and sinks

6.4.1 Heat sources due to solar radiation entering through transparent surfaces

Equation (105) shall be used to calculate solar heat gains QS,tr entering into the heated or cooled building zone through windows and other transparent surfaces.

QS,tr = FF A geff IS t (105)

where

FF is the frame factor, corresponding to the ratio of the transparent area to the total area of the element; in the absence of precise data, FF shall be assumed to be 0,7;

A is the total area of the element; the clear unfinished dimensions (i.e. gross area) are to be used;

geff is the effective total energy transmittance calculated according to equations (106) to (108);

IS is the mean solar irradiance for the entire month as specified in DIN V 18599-10;


The mean monthly solar irradiance IS is given in relation to the orientation of an element and its angle to the horizontal, these being reference climatic data as presented in DIN V 18599-10. An element is assumed to have a specific orientation if the angle between the normal of the considered element surface and the geographical orientation is less than 22,5 °. In borderline cases, the mean solar irradiance for the two orientations which may apply shall be used.

Subclause 6.4.3 describes how to calculate the effects of solar heat gains via unheated sunspaces. Solar heat gains of adjacent heated or cooled building zones are taken into consideration in the balance equations by the relevant transmission and ventilation calculations.

When calculating the effective total energy transmittance, the energy transmittance of the glazing, including any solar protection devices installed, the method of controlling the solar protection devices and the shading due to environmental factors shall be considered. In addition, increased reflection due to the oblique incidence of solar radiation as well a mean dirt load on the glazing shall be taken into consideration using default values.

Solar protection devices shall be evaluated on the basis of the total energy transmittance gtot of the combination of solar protection and glazing. The evaluation may be carried out using any of the following values: the default values given in Table 5, the results of calculations described in DIN EN 13363-1 or DIN EN 13363-2, or reliable, substantiated product data provided by the manufacturer in respect of the calorific and luminous characteristics for identical boundary conditions, and in the case of films and foils, values according to DIN EN 410. Irrespective of the source of the values, an evaluation of the solar protection devices to determine the total energy transmittance according to DIN V 18599-2 shall use the same boundary conditions as used in their evaluation in respect of lighting according to DIN V 18599-4.

Solar protection systems with slats (or louvres) are generally controlled manually or automatically in such a way that visual contact with the surroundings is maintained. The slats are therefore usually not completely shut. When calculating the total energy transmittance, a slat angle of 45° shall preferably be used. If a different slat angle is used (slat angle of 10°) to allow the use of a more favourable total energy transmittance, the corresponding characteristic values (slat angle of 10° when calculating CTL,vers,Sa,m by the detailed method) shall be used in the calculations of lighting energy.

Solar protection devices which are controlled or operated as a function of solar radiation shall be evaluated with respect to their activation. In building zones used for residential purposes, solar protection devices are only taken into consideration if they are fixed installations.

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NOTE Solar protection devices are devices for reducing the entry of solar radiation into spaces through transparent surfaces and are used to prevent overheating or for glare protection (e.g. blinds, Venetian blinds, awnings, curtains). Generally, solar protection devices are partially transparent and may be fixed (permanently active) or movable (variable), i.e. active only part of the time. Movable solar protection devices are opened or shut (i.e. activated) depending on the solar irradiance. This may be achieved by manual controls, timer controls or intensity-dependent controls.

Hence the following distinction is made, depending on the type of solar protection device:

⎯ no solar protection

geff = FS Fw FV g⊥ (106)

⎯ fixed solar protection device

geff = FS Fw FV gtot (107)

⎯ movable solar protection device

geff = FW FV min⎭⎬⎫

⎩⎨⎧ −+

⊥⊥

gFgg

Stot )1( aa (108)

Since activation of the solar protection device depends on the shading of the building, it cannot be evaluated independently of this factor. For simplified evaluations, the values of the factor with the greater effect (i.e. external shading or movable solar protection) can be used.

Equations (106) or (107) shall be applied for building zones used for residential purposes.

Where

FS is the shading correction factor to account for shading by the surroundings, other buildings or parts of the building, calculated using equation (109);

Fw is the correction factor due to oblique incidence of radiation, equal to 0,9;

FV is the dirt depreciation factor from DIN V 18599-10;

g⊥ is the total energy transmittance of the glazing (without solar protection) according to DIN EN 410 for perpendicular incidence of radiation (see Table 5 for default values);

gtot is the total energy transmittance taking into consideration the solar protection device either according to Table 5, or calculated as described in DIN EN 13363-1 or DIN EN 13363-2, or on the basis of reliable, substantiated calorific and luminous product data provided by the manufacturer for identical boundary conditions;

a is the parameter for assessing the activation of movable solar protection devices listed in Table A.4 and Table A.5, respectively.

Since DIN EN 13363-1 makes no provision for calculation of a slat angle of 10°, the results obtained for a slat angle of 0° and a slat angle of 45° shall be weighted as follows in an evaluation according to DIN EN 13363-1: gtot,15° = 2/3 gtot,0° + 1/3 gtot,45°.

For the parameter a, used for assessing the activation of the solar protection, a distinction shall be made between manually controlled or timer-controlled operation, on the one hand, and irradiance-controlled operation, on the other hand. In Table A.4, values are given for manually controlled or timer-controlled operation; Table A.5 gives values for intensity-controlled operation. Both tables give separate values for the summer and the winter half-years, respectively.

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Table 5 gives default values for the total energy transmittance for common solar protection systems and various types of glazing. In addition, the thermal transmittance of the glazing Ug and the transmittance for solar radiation τe and visible light τD65 are given. Corresponding values shall be used for calculating the solar heat gains, the transmission heat according to 6.2 as well as the energy need for lighting according to DIN V 18599-4.

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Table 5 — Default values for characteristics of glazing and solar protection devices a

with external solar protection with internal solar protection

external Venetian

blindb (10° position)

external Venetian

blind (45° position)

roller blind(Markisolette)

internal Venetian

blindb (10° position)

internal Venetian

blind (45° position)

textile roller blind film

Characteristics, without solar

protection device w

hite

dark

gre

y

whi

te

dark

gre

y

whi

te

grey

whi

te

light

gre

y

whi

te

light

gre

y

whi

te

grey

c

whi

tec

Type of glazing

Ugd g⊥ τe τD65 gtot gtot gtot gtot gtot gtot gtot gtot gtot gtot gtot gtot gtot

single 5,8 0,87 0,85 0,90 0,07 0,13 0,15 0,14 0,22 0,18 0,30 0,40 0,38 0,46 0,25 0,52 0,26

double 2,9 0,78 0,73 0,82 0,06 0,09 0,13 0,10 0,20 0,14 0,34 0,44 0,41 0,49 0,29 0,52 0,30

triple 2,0 0,7 0,63 0,75 0,05 0,07 0,11 0,08 0,18 0,11 0,35 0,43 0,40 0,47 0,31 0,50 0,32

MPIGe double

1,7 0,72 0,6 0,74 0,05 0,07 0,11 0,07 0,18 0,11 0,35 0,44 0,41 0,48 0,30 0,51 0,32

MPIGe double

1,4 0,67 0,58 0,78 0,04 0,06 0,10 0,06 0,17 0,10 0,35 0,43 0,40 0,47 0,31 0,49 0,32

MPIGe double

1,2 0,65 0,54 0,78 0,04 0,05 0,10 0,06 0,16 0,09 0,35 0,43 0,40 0,46 0,31 0,48 0,32

MPIGe triple

0,8 0,5 0,39 0,69 0,03 0,04 0,07 0,04 0,13 0,07 0,32 0,37 0,35 0,39 0,30 0,40 0,31

MPIGe triple

0,6 0,5 0,39 0,69 0,03 0,03 0,07 0,03 0,12 0,06 0,33 0,37 0,36 0,39 0,30 0,40 0,31

SPGf double

1,3 0,48 0,44 0,59 0,04 0,05 0,08 0,06 0,13 0,08 0,31 0,35 0,34 0,37 0,29 0,38 0,30

SPGf double

1,2 0,37 0,34 0,67 0,03 0,05 0,07 0,05 0,11 0,07 0,27 0,29 0,29 0,30 0,26 0,31 0,26

SPGf double

1,2 0,25 0,21 0,40 0,03 0,05 0,06 0,05 0,09 0,07 0,20 0,21 0,21 0,22 0,20 0,22 0,20

Characteristics of solar protection device

Transmittance τe,B 0 0 0 0 0,22 0,07 0 0 0 0 0,11 0,30 0,03

Reflectance ρe,B 0,74 0,085 0,74 0,085 0,63 0,14 0,74 0,52 0,74 0,52 0,79 0,37 0,75

a gtot calculated as described in DIN EN 13363-1, for film as described in DIN EN 410. b Systems with slats are to be assessed preferably for a 45° slat setting. The values given for 10° slat settings have been determined

by weighting: gtot,10° = 2/3 gtot,0° + 1/3 gtot,45°. c These systems do not provide adequate solar protection. Subsequent installation of glare protection reduces light transmission but

hardly affects gtot. d Design value from DIN V 4108-4 in W/(m2 · K) (including a correction value of 0,1 W/(m2 · K)). e MPIG: multiple insulating glazing f SPG: solar protection glazing

⎯ External shading reduction factor FS

The external shading reduction factor FS takes into account:

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⎯ shading by other buildings;

⎯ any shading by topographic features (e.g. hills);

⎯ shading by overhangs and fins that are part of the same building.

A value of 0,9 may be assumed for FS in normal applications.

Annex A contains tables of correction factors for more detailed assessments. The correction factors represent the degree by which shading due to other building elements or the surroundings reduces the solar radiation, on average, in the winter half-year and in the summer half-year. These take into account the shading angle and the angle and orientation of the surface of the element being assessed. Different factors are obtained for shading from below (shading from horizon), from above (by overhangs) and from the sides (fins). If the building element is shaded from various directions, the lowest shading correction factor is to be used.

FS = min (Fh; Fo; Ff) (109)

where

Fh is the partial shading correction factor for the horizon (e.g. by other buildings, topography) as given in Table A.1;

Fo is the partial shading correction factor for overhangs (e.g. canopies, balconies etc.) above the element being considered, as given in Table A.2;

Ff is the partial shading correction factor for fins as given in Table A.3.

For elements which are shaded over a large area from different directions, a mean value is to be used; FS = 1 when there is no shading.

6.4.2 Solar heat gains via opaque building elements

The heat sources and sinks due to solar radiation on opaque building elements and long-wave radiative heat transfer from such elements shall be calculated using equations (110) and (111), respectively. For elements with transparent thermal insulation, equation (113) shall be used.

QS,op = Rse U A (α IS – Ff hr Δϑer) t for α IS > Ff hr Δϑer (heat source) (110)

QS,op = Rse U A (Ff hr Δϑer – α IS) t for α IS < Ff hr Δϑer (heat sink) (111)

where

Rse is the external surface resistance;

U is the thermal transmittance of the element;

A is the total area of the element in a specific orientation;

α is the solar radiation absorption coefficient of the element (see Table 6 for default values);

IS is the global solar irradiance for the orientation of the element surface as specified in DIN V 18599-10;

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Ff is the form factor for the relationship between the building element and the sky: Ff = 1 for horizontal element surfaces and surfaces with a surface angle of up to 45°; Ff = 0,5 for vertical elements and elements with a surface angle of more than 45°;

hr is the external radiative heat transfer coefficient obtained using equation (112);

Δϑer is the mean difference between the temperature of the ambient air and the apparent sky temperature; for simplified calculations Δϑer can be assumed to be 10 K;


Table 6 — Default values for solar radiation absorption coefficients of various surfaces for the energy-relevant part of the solar radiation spectrum

Surface Solar radiation absorption

coefficient α

Wall surfaces:

— light paintwork 0,4

— muted paintwork 0,6

— dark paintwork 0,8

— clinker brick wall 0,8

— light-coloured brick wall 0,6

Roofs (characteristics):

— brick-red 0,6

— dark surfaces 0,8

— metal (bright) 0,2

— tar-paper (sanded) 0,6

A rough approximation of the value of hr is obtained using equation (112):

hr = 5 ε in W/(m2 · K) (112)

where

ε is the emissivity for thermal radiation of the external surface. If the values are not known, ε shall be assumed to be equal to 0,9.

Solar heat gains in opaque building elements with transparent thermal insulation shall be calculated as follows:

QS,op,TI = Re U A FF FS Fw gTI α IS t (113)

where

Re is the external thermal resistance of the element (calculated in an outward direction, starting from the absorbent layer; thermal resistance of the transparent insulation, including the external surface resistance);

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U is the total thermal transmittance of the element;


FS is the external shading reduction factor from 6.4.1;

FF is the frame factor for the element;

Fw is the correction factor for oblique incidence of radiation, Fw = 0,9 (in cases where oblique radiation has already been taken into consideration when determining gTI, Fw = 1 is to be used);

gTI is the total energy transmittance of the transparent thermal insulation, as certified (if no accurate data are available, gTI is assumed to be equal to 0,35);

α is the solar radiation absorption coefficient of the transparent thermal insulation (in cases where solar radiation absorption has already been taken into consideration when determining gTI, α = 1 is to be used);

IS is the global solar irradiance for the respective orientation as specified in DIN V 18599-10;


NOTE See [3] for a more detailed method of determining solar heat gains due to transparent thermal insulation systems. For special transparent thermal insulation systems (e.g. with integrated shading devices) monthly values of gTI can be determined by measuring the angle-dependent g value and determining the effective monthly values by simulation for one-hour intervals, similar to the method described in 6.4.1.

Other forms of solar heat gains via ventilated solar walls (Trombe walls) or via ventilated elements forming part of the building envelope (dynamic thermal insulation) are described in DIN EN 832.

6.4.3 Solar heat gains via unheated or uncooled sunspaces (glazed annexes)

Heated or cooled sunspaces not separated from the adjacent zone by a partition shall be calculated as heated or cooled building zones. Subclause 6.4.3.3 contains information on assessing glass double façades.

The glazing of the sunspace shall be taken into consideration when calculating the heat input in the heated or cooled building zones due to solar radiation. The direct solar heat gains via transparent building elements are thus calculated using equation (114).

Direct solar heat gains due to opaque elements of the partition shall be ignored. These are assessed indirectly through being included in the temperature increase within the sunspace.

The mean temperature in the sunspace is calculated as described in 6.4.1 and using equation (38), or equation (39) for sunspaces bordering on several zones. When calculating the heat flow Φu which is needed for determining the temperature, the entire radiant heat entering through the external glazing of the sunspace shall be taken into account, as well as any internal heat sources (see equation (115)). The radiant heat QS,tr which is transferred directly via transparent building elements of the partition into the building zone being assessed shall be subtracted from this.

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Figure 4 — Diagram representing the thermal quantities to be taken into consideration for sunspaces (glazed annexes)

External shading and solar protection shall be calculated for the element under consideration as follows. ⎯ Shading and solar protection devices in connection with the transparent elements of the partition shall be

taken into account when calculating the direct heat gains QS,tr in the building zones. Solar protection devices shall be taken into consideration when calculating the total energy transmittance gtot of the internal glazing. For external solar protection devices, it is of no account whether these are located inside or in front of the sunspace.

⎯ When calculating the heat flow Φu into the sunspace, the shading and solar protection factors of the external glazing shall be determined. Solar protection and shading of the external glazing shall be taken into consideration in the calculations of the total energy transmittance of the external glazing. Solar protection of the internal glazing need not be considered.

6.4.3.1 Direct solar heat gains in the building zone

The solar heat gains QS,tr due to transparent elements of the partitions shall be calculated as described in 6.4.1, taking the additional glazing (between the sunspace and the external environment) into consideration.

QS,tr = FF,iu Aiu geff,iu FF,ue τe,ue IS t (114)

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where

FF,iu is the frame factor accounting for the proportion of frame on the internal glazing (corresponding to the ratio of the transparent area to the total area Aiu); in the absence of precise data, FF,iu shall be assumed to be 0,7;

Aiu is the area of the element of the partition separating the building zone being considered from the unheated sunspace (using the clear unfinished dimensions);

geff,iu is the total effective energy transmittance of the transparent part of the element, calculated using equations (106) to (108) and taking the following into consideration:

— the total energy transmittance gtot of the internal glazing including solar protection devices,

— the activation of solar protection devices,

— shading by surroundings and parts of the building,

— deviation of the radiation incidence from the perpendicular,

— dirt on the glazing;

FF,ue is the frame factor accounting for the proportion of frame on the external glazing (corresponding to the ratio of the transparent area to the total area); in the absence of precise data, FF,ue shall be assumed to be 0,9;

τeu,e is the transmittance of the external glazing (see Table 5 for default values);

IS is the global solar irradiance for the orientation of the partition as specified in DIN V 18599-10.

6.4.3.2 Heat gains affecting the unheated or uncooled sunspace (glazed annex)

The heat flow into the unheated or uncooled sunspace shall be calculated in order to determine the temperature of the space:

∑∑∑ +−= I,utrS,

S,uu ΦΦΦt

Q (115)

where

ΣΦS,u is the total incident solar radiation in the sunspace via all transparent external elements, obtained by means of equation (116);

ΣQS,tr is the total solar radiation passing through the sunspace into the adjacent building zone, calculated using equation (114) for all transparent elements of the partition separating the building zone considered and the unheated sunspace;

ΣΦI,u is the sum of the heat flows due to internal heat sources in the sunspace (generally zero, or determined as described in 6.5).

The solar radiation entering the sunspace shall be calculated using equation (116):

ΦS,u = FF,ue Aue geff,ue IS (116)

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where

FF,ue is the frame factor to account for the proportion of frame on the external glazing (corresponding to the ratio of the transparent area to the total area), in the absence of precise data, FF,ue shall be assumed to be 0,9;

Aue is the area of each external surface of the sunspace with a specific orientation;

geff,ue is the effective total energy transmittance of the transparent part of the external glazing calculated using equations (106) to (108), taking the following factors into consideration:

— shading,

— the effective total energy transmittance of the internal glazing taking into account solar protection devices and their activation,

— deviation of the solar radiation incidence from the perpendicular,

— dirt on the glazing;

IS is the global solar irradiance for the orientation of the partition, as specified in DIN V 18599-10.

6.4.3.3 Calculation of balances for glass double façades

As long as there is no generally approved method of calculating energy characteristics of glass double façades, all façades of this type which are subdivided into individual storeys may be treated as unheated or uncooled sunspaces as described in 6.4.3 and 6.1.3.3, however with the following deviating boundary conditions:

⎯ when using equation (94) to calculate the ventilation heat transfer coefficient, an air change rate of nue = 10 h–1 shall be assumed (irrespective of the temperature occurring within the glass double façade);

⎯ in the absence of precise data, the frame factor FF,ue shall be assumed to be equal to 0,95.

6.5 Internal heat sources and sources of cold

6.5.1 Internal heat sources in residential buildings

In the case of residential buildings, the internal heat sources due to persons, machinery, equipment and lighting shall be added and treated as a single quantity. Heat sources due to the operation of heating systems shall be specified separately. Sources of cold shall be neglected.

QI,source,WG = QI,source,p + QI,source,L + QI,source,fac = qI AB (117)

where

q I is the specific mean daily dissipation of heat by persons, machinery, equipment and lighting in residential buildings in relation to the reference area as specified in DIN V 18599-10;

AB is the reference area of the building zone.

6.5.2 Heat sources due to persons

DIN V 18599-10 gives area-specific values of the heat dissipated by persons in relation to the respective usage profiles. These are used to determine the mean heat dissipation:

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QI,source,p = qI,p AB (118)

where

qI,p is the specific mean daily heat dissipation by persons, in relation to the reference area as specified in DIN V 18599-10;

AB is the reference area of the building zone.

If the usage deviates significantly from the default values, the more detailed usage profiles given in DIN V 18599-10 can be used; if necessary, the given value shall be converted to a value for the mean daily heat dissipation, taking into consideration the occupancy (number of persons) and usage times.

6.5.3 Heat sources and sinks due to machinery and equipment

DIN V 18599-10 gives area-specific values of the heat dissipated in the building zone due to the operation of machinery and equipment. These shall be used when calculating the actual amount with equation (119). Equipment which generates cooling energy (e.g. refrigerated sales counters) and which extract the heat outside the building zone being assessed shall be treated as a heat sink (see equation (120)).

QI,source,fac = qI,fac AB (119)

QI,sink,fac = qI,sink,fac AB (120)

where

qI,fac is the specific mean daily heat dissipation by machinery and equipment, in relation to the reference area as specified in DIN V 18599-10;

AB is the reference area of the building zone;

qI,sink,fac is the specific mean daily cooling energy dissipated by refrigeration appliances with refrigeration units outside the building zone, in relation to the reference area as specified in DIN V 18599-10.

It is to be noted that the internal heat loads usually specified per square metre in technical installation engineering (without reference to AB) do not correspond to the values qI,fac used in the calculations described in this document and may need to be converted. In such cases, the time relation shall also be observed: qI,fac is the mean daily sum of heat gains.

If the usage deviates significantly from the default values, the more detailed usage profiles given in DIN V 18599-10 can be used; if necessary, the specified value shall be converted to a mean daily heat gain.

6.5.4 Internal heat sources/heat sinks due to movement of materials

If goods or materials with temperatures differing significantly from the internal temperature are regularly brought into or taken out of the building zone (e.g. in a production facility), these shall be considered to be heat sources or heat sinks and shall be taken into consideration in equations (121) and (122), respectively.

QI,source,goods = c m⋅ (ϑ in – ϑout) t for ϑ in > ϑout (121)

QI,sink,goods = c m⋅ (ϑout – ϑ in) t for ϑ in < ϑout (122)

where

c is the specific heat capacity of the material being moved;

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m⋅ is the mass transport rate of the material ;(24mm =& whereby m is the mean mass of material

transported in a 24 h period);

ϑ in is the mean temperature in the time interval at which the material, goods etc. are brought into the building zone;

ϑout is the temperature of the material or goods leaving the building zone (if not otherwise known, the internal temperatureϑ i);

t is the length of the calculation step (t = 24 h).

6.5.5 Heat sources due to artificial lighting

The electrical energy requirement QI,L,elektr of artificial lighting shall generally be used directly to determine the heat gains due to artificial lighting QI,source,L. The calculation methods described in DIN V 18599-4 shall be used. In building zones with air-handling luminaires, in which part of the heat generated by the lighting is transported directly out of the zone with extract air, the heat gains due to artificial lighting shall be assessed with the lighting heat gain coefficient µL.

Q i,L = µL Qi,L,elektr (123)

where

µL is the lighting heat gain coefficient (see Table 7 for default values).

Q i,L,elektr is the mean daily electrical energy input for artificial lighting (see DIN V 18599-4).

Where air-handling luminaires are not used, µL = 1.

NOTE See [2] for a detailed definition of µL.

Key

a) Extraction via space above false ceiling

b) Extraction via a separate connected air duct

Figure 5 — Examples of two types of air-handling luminaire

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Table 7 — Default values for lighting heat gain coefficients µL for air-handling luminaires

Fluorescent lamps in ceiling systems

Air flow in relation to the luminaire power requirements in m3/(h·W) 0,2 0,3 0,5 1,0

µL for extraction via space above false ceiling 0,80 0,70 0,55 0,45

µL for extraction via uninsulated extract air ducts 0,45 0,40 0,35 0,30

µL for extraction via insulated extract air ducts 0,40 0,35 0,30 0,25

6.5.6 Heat sources and sinks due to heating, cooling, domestic hot water supply and ventilation systems

When calculating the effects of heat sources and sinks due to technical building systems (heating, cooling, ventilation and domestic hot water systems), all uncontrolled heat and cooling energy flows due to distribution piping and air ducts passing through the building zone, and also those due to heat storage vessels, heat generators, chillers and fans located within the building zone, shall be taken into consideration. In each case, only those parts of the energy flows which affect the building zone being assessed shall be counted. The heat and cold gains shall be determined as specified in the relevant parts of the DIN V 18599 series.

QI,source,h = QI,w + QI,h + QI,vh + QI,ch (124)

QI,sink,c = QI,vc + QI,c (125)

where

QI,w is the uncontrolled heat input into the zone due to the domestic hot water system (e.g. distribution, storage and, where applicable, generation within the zone) according to DIN V 18599-8, expressed as a mean daily value;

QI,h is the uncontrolled heat input into the zone due to the heating system (e.g. distribution, storage and, where applicable, generation within the zone), according to DIN V 18599-5 and DIN V 18599-7 (sum of the two values), expressed as a mean daily value;

QI,vh is the uncontrolled heat input into the zone due to mechanical ventilation (e.g. distribution and emission losses due to air ventilation), according to DIN V 18599-6 (QI,vh = Q I,rv,i) and DIN V 18599-7, expressed as a mean daily value;

QI,ch is the uncontrolled heat input into the zone due to the cooling system/cold generation (where applicable, due to generation within the zone), according to DIN V 18599-7, expressed as a mean daily value;

QI,vc is the uncontrolled cold input into the zone due to mechanical ventilation (e.g. distribution losses), according to DIN V 18599-6 (QI,vh = QI,rv,c,i) and DIN V 18599-7, expressed as a mean daily value;

QI,c is the uncontrolled cold input into the zone due to the cooling system/cold generation (e.g. distribution, storage and, where applicable, generation within the zone), as described in DIN V 18599-6 and DIN V 18599-7, expressed as a mean daily value.

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If it is not possible to identify the heat and cold input separately for work days and weekends, these shall be classified according to other logical criteria.

NOTE The heat sources and sinks due to distribution piping and ducts in a building can be distributed globally over the individual building zones; rules are given in the relevant parts of the DIN V 18599 series.

6.6 Taking into account stored heat between days of usage and non-usage

The heat escaping from elements at the weekend or during holiday periods and stored during periods of usage shall

⎯ be deducted from the energy need for heating for the period of non-usage,

⎯ be taken into account as a heat sink in the heating balance for the period of usage.

The quantity of heat shall be the same for the days of usage and non-usage for the month as a whole and shall be assessed according to the mean number of periods of reduced heating in the month. The quantities shall be given in relation to a one-day period (24 h).

The escaping heat to be included in the balance shall be limited by the maximum permitted temperature reduction during reduced heating operation and by the total heat requirement during the period of reduced heating (without taking into account the escaping heat).

The stored heat to be included in the balance for weekend and holiday periods shall be calculated according to equation (126):

⎟⎟⎠

⎞⎜⎜⎝

⎛−

−= sourcesink

we

NAi,wirk

we

hi,sollh,i,wirkweb,C, ,

Δ,

)(2minΔ QQ

CCQ η

ϑϑϑaa

(126)

If ϑi,h,soll < ϑi,h, then: ΔQC,b,we = 0

where

Cwirk is the effective heat capacity to 6.7.1;

ϑi,h,soll is the mean internal temperature according to DIN V 18599-10 in periods of normal heating operation;

ϑi,h is the reference internal temperature for reduced weekend operation according to equation (30);

Δϑi,NA is the permitted reduction in the internal temperature according to DIN V 18599-10 for periods of reduced heating;

αwe is the average number of days of non-usage per week (in the absence of specific data, αwe = (1 – dnutz/365) × 7);

Qsink is the sum of heat sinks in the building zone during weekend or holiday operation;

Qsource is the sum of heat sources in the building zone during weekend or holiday operation;

η is the monthly utilization factor of the heat sources for weekend or holiday operation.

When considering days of usage, the following applies: ΔQC,b,nutz = 0 (see also 5.2.4).

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In addition, when considering days of usage, the stored heat from equation (127) shall be taken as a heat sink in the heating balance:

nutz

weweb,C,nutzsink,C,

ΔΔ

ddQ

Q = (127)

where

dnutz is the number of days in the month with normal usage (see 5.2.5);

dwe is the number of weekend days or days holiday in the month (see 5.2.5).

For days of non-usage the following applies: ΔQC,sink,nutz = 0 (see also 5.2.4 and 5.3.6).

In the balance of the energy need for cooling, the following applies: ΔQC,sink = 0 for days of usage and non-usage (see also 5.2.4 and 5.3.6).

6.7 Utilization factors of heat sources

6.7.1 Effective heat capacity (thermal mass)

The effective heat capacity Cwirk shall be calculated as described in DIN EN ISO 13786.

Generally, the simplified method as described in Annex A of DIN EN ISO 13786:1999-12 should be used (10 cm rule). For elements with covered storage masses (e.g. raised floors or suspended ceilings), the detailed method is to be used.

For simplified evaluations, the following blanket values relating to the reference area AB, as expressed by equations (128) to (130) may be used. This shall be specifically stated in the evaluation report.

For building zones with low thermal mass:

Cwirk = 50 Wh/(m2 · K) AB (128)

For building zones with medium thermal mass:

Cwirk = 90 Wh/(m2 · K) AB (129)

For building zones with high thermal mass:

Cwirk = 130 Wh/(m2 · K) AB (130)

Building zones are classified in respect of thermal mass as follows:

The default value applies to building zones with low thermal mass.

Building zones with the following characteristics are to be classified as being of “medium thermal mass”:

⎯ solid internal and external building elements (with a density equal to or greater than 600 kg/m3);

⎯ no suspended or covered ceilings;

⎯ no internal insulation of external building elements;

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⎯ no high rooms (e.g. sports halls, museums etc.).

Building zones with the following characteristics are to be classified as being of “high thermal mass”:

⎯ solid internal and external building elements (density equal to or greater than 1 000 kg/m3);

⎯ no suspended or covered ceilings;

⎯ no internal insulation of external building elements;

⎯ no high rooms (e.g. sports halls, museums etc.).

6.7.2 (Thermal) time constant

The (thermal) time constant τ of the building zone shall be calculated using equation (131):

ϑ∑∑ ++==

mech,V,V,T,

wirkwirkHHH

CH

C

kk

jj

τ (131)

where

Cwirk is the effective heat capacity;

H is the heat transfer coefficient of the building zone, calculated on the basis of the transmission and ventilation heat transfer coefficients;

∑j

jHT, is the sum of the transmission heat transfer coefficients for all elements j of the thermal envelope of the building zone to be included in the balance calculations according to 6.2;

⎯ for direct transmission to the external environment as described in 6.2.1,

⎯ for transmission through unheated or uncooled spaces to the external environment as described in 6.2.2,

⎯ for transmission to adjacent zones as described in 6.2.3,

⎯ for transmission through the ground as described in 6.2.1 or 6.2.4.

∑k

,kH V is the sum of all ventilation heat transfer coefficients for supply air flow with temperatures equal to that of the external air;

⎯ for infiltration as described in 6.3.1 and

⎯ for window airing as described in 6.3.2;

HV,mech,ϑ is the temperature-weighted heat transfer coefficient of mechanical ventilation, calculated using equations (132) to (134).

⎯ For HVAC systems with cooling functions, the air volume flow shall be calculated on the basis of the given supply air temperature (in relation to a standard temperature difference of 6 K below the internal temperature).

HV,mech,ϑ = HV,mech K 6

mechV,i ϑϑ − (132)

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where

HV,mech is the heat transfer coefficient of mechanical ventilation (see 6.3.3);

ϑi for heating: ϑI = ϑI,h,soll; for cooling: ϑI = ϑI,h,soll – 2K (internal set-point temperatures according to DIN V 18599-10, (see 6.1));

ϑV,mech is the minimum supply air temperature of the mechanical ventilation system.

⎯ For HVAC systems without cooling functions and ventilation systems for residential buildings, the uncorrected ventilation heat transfer coefficient of the system-driven air flow shall be used in equation (133), in which case:

HV,mech,ϑ = HV,mech (133)

⎯ For an air-heating system which provides supply air at temperatures equal to or above the internal set-point temperature:

HV,mech,ϑ = 0 (134)

Air-heating systems are usually specifically designed to meet the heating requirement of the building zone and are to be neglected when calculating the heat-source/heat-sink balances.

6.7.3 Utilization factor

The utilization factor η as defined in DIN EN 832 can be approximated using equations (135) and (136).

111

+−

−= a

a

γγη for γ ≠ 1 (135)

1+=

aaη for γ = 1 (136)

where a is a numerical parameter determined by applying equation (137).

a = a0 + 0τ

τ = 1 + h 16

τ (137)

where

τ is the (thermal) time constant of the building zone calculated using equation (131);

γ the ratio of heat source to heat sinks calculated using equation (138);

a0 and τ0 are numerical parameters, specified as a0 = 1 and τ0 = 16 h.

The ratio of heat sources to heat sinks, γ, is calculated separately for each month as the ratio of the sum of all heat sources to the sum of all heat sinks in the calculation period.

sink

sourceQ

Q=γ (138)

NOTE For Qsink = 0, η is also equal to 0.

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6.7.4 Limits for the utilization factor

For the balance of the energy need for heating, the following applies:

if 1 – (η γ) < 0,01, then η = 1/γ, (Qh,b = 0). (139)

For the balance of the energy need for cooling, the following applies:

if (1 – η) γ < 0,01 then η = 1, (Qc,b = 0). (140)

In applications where the basic mechanical air change rates are high, i.e.

( )mechiaap,

C,maxmech ϑϑρ −

≥c

QV

&& , η shall be given a value of 1. (141)

In the above,

V⋅mech is the minimum air volume flow of the system as specified in DIN V 18599-3 or DIN V 18599-10, or the volume flow calculated using equation (86);

Q⋅C,max is the maximum cooling load calculated using equation (C.1);

ϑi is the internal set-point temperature of the building zone for cooling, ϑi,c,soll, as specified in DIN V 18599-10;

ϑV,mech is the minimum supply air temperature calculated using equations (90) to (93);




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Annex A (normative)

Shading factors and movable solar protection devices

A.1 General

The factors describing external shading and activation of solar protection devices shall be included in the calculation of the effective total energy transmittance. These factors are to be considered independently of each other.

Different values shall be assumed for the summer half-year and the winter half-year.

For the purposes of this Annex, the summer half-year covers the months April to September.

Accordingly, the winter half-year covers the months October to March.

A.2 Correction factors for external shading

The following types of external shading shall be taken into consideration:

⎯ shading by other buildings (shading from the horizon; see Table A.1 for values of Fh);

⎯ shading by topographic features (e.g. hills, trees, etc.), also classed as shading from the horizon (see Table A.1 for values of Fh);

⎯ overhangs, projections above the element being assessed (see Table A.2 for values of Fo);

⎯ fins, projections at the sides of the element being assessed (see Table A.3 for values of Ff);

The correction factors also depend on the shading angle (see Figures A.1 to A.3), the orientation (of the normal to the surface of the building element), the surface angle (angle between surface and horizontal) and the season. A distinction is made between the winter half-year and the summer half-year.

Figure A.1 —Horizon angle

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Table A.1 — Partial shading correction factors Fh for various horizon angles and surface angles

Partial shading correction factors Fh for various horizon angles and a vertical surface

Horizon angle

Surface angle Period North NE/NW East/West SE/SW South

vertical winter 1,00 1,00 1,00 1,00 1,00 0°

vertical summer 1,00 1,00 1,00 1,00 1,00

vertical winter 0,90 0,88 0,83 0,88 0,90 10°

vertical summer 0,88 0,88 0,91 0,94 0,96

vertical winter 0,80 0,78 0,59 0,58 0,58 20°

vertical summer 0,80 0,74 0,79 0,86 0,93

vertical winter 0,73 0,70 0,49 0,41 0,38 30°

vertical summer 0,75 0,63 0,65 0,76 0,88

vertical winter 0,67 0,65 0,44 0,32 0,28 40°

vertical summer 0,71 0,55 0,53 0,64 0,78

Partial shading correction factors Fh for various horizon angles and a surface angle of 60°

Horizon angle


60° winter 1,00 1,00 1,00 1,00 1,00 0°

60° summer 1,00 1,00 1,00 1,00 1,00

60° winter 0,90 0,89 0,86 0,90 0,91 10°

60° summer 0,89 0,90 0,92 0,95 0,97

60° winter 0,80 0,77 0,63 0,61 0,60 20°

60° summer 0,78 0,77 0,81 0,88 0,93

60° winter 0,70 0,67 0,49 0,42 0,39 30°

60° summer 0,68 0,64 0,69 0,78 0,86

60° winter 0,61 0,59 0,41 0,31 0,28 40°

60° summer 0,60 0,52 0,56 0,65 0,72


Horizon angle


45° winter 1,00 1,00 1,00 1,00 1,00 0°

45° summer 1,00 1,00 1,00 1,00 1,00

45° winter 0,91 0,90 0,88 0,91 0,91 10°

45° summer 0,91 0,92 0,93 0,96 0,97

45° winter 0,81 0,79 0,67 0,63 0,62 20°

45° summer 0,81 0,81 0,84 0,89 0,93

45° winter 0,72 0,68 0,52 0,44 0,41 30°

45° summer 0,71 0,68 0,72 0,79 0,85

45° winter 0,62 0,59 0,43 0,33 0,30 40°

45° summer 0,61 0,56 0,59 0,66 0,70

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Table A.1 (concluded)


Horizon angle


30° winter 1,00 1,00 1,00 1,00 1,00 0°

30° summer 1,00 1,00 1,00 1,00 1,00

30° winter 0,93 0,93 0,91 0,92 0,93 10°

30° summer 0,95 0,94 0,95 0,96 0,97

30° winter 0,85 0,82 0,72 0,67 0,66 20°

30° summer 0,87 0,86 0,87 0,90 0,93

30° winter 0,76 0,72 0,57 0,49 0,46 30°

30° summer 0,77 0,75 0,77 0,81 0,85

30° winter 0,57 0,53 0,41 0,33 0,31 40°

30° summer 0,59 0,58 0,60 0,64 0,66

Partial shading correction factors Fh for various horizon angles and a horizontal surface

Horizon angle

Surface angle Period All orientations

horizontal winter 1,00 0°

horizontal summer 1,00









Figure A.2 —Overhang angle

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Table A.2 — Partial shading correction factors Fo for horizontal overhangs and various surface angles

Partial shading correction factors Fo for various overhang angles and a vertical surface

Overhang angle


vertical winter 1,00 1,00 1,00 1,00 1,00 0°

vertical summer 1,00 1,00 1,00 1,00 1,00

vertical winter 1,00 1,00 0,97 0,96 0,97 30°

vertical summer 0,99 0,95 0,92 0,88 0,81

vertical winter 1,00 0,99 0,93 0,90 0,90 45°

vertical summer 0,98 0,91 0,85 0,77 0,68

vertical winter 1,00 0,98 0,87 0,80 0,79 60°

vertical summer 0,96 0,85 0,76 0,65 0,60

Partial shading correction factors Fo for various overhang angles and a surface angle of 60°

Overhang angle


60° winter 1,00 1,00 1,00 1,00 1,00 0°

60° summer 1,00 1,00 1,00 1,00 1,00

60° winter 1,00 0,99 0,98 0,99 1,00 30°

60° summer 0,96 0,95 0,96 0,96 0,94

60° winter 1,00 0,99 0,97 0,99 1,00 45°

60° summer 0,95 0,91 0,92 0,91 0,87

60° winter 1,00 0,98 0,95 0,97 1,00 60°

60° summer 0,93 0,87 0,86 0,83 0,74


Overhang angle


45° winter 1,00 1,00 1,00 1,00 1,00 0°

45° summer 1,00 1,00 1,00 1,00 1,00

30° 45° winter 1,00 0,99 0,99 1,00 1,00

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45° summer 0,87 0,93 0,96 0,97 0,98

45° winter 1,00 0,98 0,97 0,99 1,00 45°

45° summer 0,84 0,89 0,92 0,94 0,95

45° winter 1,00 0,98 0,95 0,99 1,00 60°

45° summer 0,82 0,84 0,88 0,89 0,89

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Overhang angle


30° winter 1,00 1,00 1,00 1,00 1,00 0°

30° summer 1,00 1,00 1,00 1,00 1,00

30° winter 0,99 0,97 0,96 1,00 1,00 30°

30° summer 0,83 0,91 0,95 0,98 0,99

30° winter 0,99 0,96 0,97 1,00 1,00 45°

30° summer 0,73 0,85 0,92 0,96 0,99

30° winter 0,99 0,95 0,95 0,99 1,00 60°

30° summer 0,67 0,80 0,88 0,92 0,97

Partial shading correction factors for horizontal surfaces shall be deduced from the geometrical configuration and the shading from the horizon as listed in Table A.1.

Figure A.3 —Lateral shading angle (fin angle)

Table A.3 — Partial shading correction factors Ff for lateral shading

Partial shading correction factors Ff for various fin angles and a vertical surface

Fin angle Surface angle Period North NE/NW East/West SE/SW South

vertical winter 1,00 1,00 1,00 1,00 1,00 0°

vertical summer 1,00 1,00 1,00 1,00 1,00

vertical winter 1,00 0,97 0,86 0,89 0,89 30°

vertical summer 0,94 0,90 0,94 0,90 0,88

vertical winter 1,00 0,96 0,79 0,84 0,81 45°

vertical summer 0,93 0,84 0,90 0,84 0,82

vertical winter 1,00 0,96 0,70 0,75 0,70 60°

vertical summer 0,93 0,76 0,84 0,76 0,75

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Partial shading correction factors Ff for various fin angles and a surface angle of 60°


60° winter 1,00 1,00 1,00 1,00 1,00 0°

60° summer 1,00 1,00 1,00 1,00 1,00

60° winter 1,00 0,96 0,85 0,89 0,90 30°

60° summer 0,89 0,87 0,93 0,90 0,88

60° winter 1,00 0,95 0,78 0,83 0,84 45°

60° summer 0,87 0,79 0,88 0,84 0,81

60° winter 1,00 0,95 0,69 0,75 0,73 60°

60° summer 0,87 0,69 0,80 0,76 0,71



45° winter 1,00 1,00 1,00 1,00 1,00 0°

45° summer 1,00 1,00 1,00 1,00 1,00

45° winter 1,00 0,93 0,84 0,88 0,90 30°

45° summer 0,82 0,87 0,91 0,89 0,88

45° winter 0,99 0,92 0,75 0,82 0,83 45°

45° summer 0,75 0,78 0,85 0,83 0,81

45° winter 0,99 0,92 0,69 0,73 0,74 60°

45° summer 0,69 0,65 0,75 0,74 0,71



30° winter 1,00 1,00 1,00 1,00 1,00 0°

30° summer 1,00 1,00 1,00 1,00 1,00

30° winter 1,00 0,95 0,83 0,89 0,90 30°

30° summer 0,84 0,86 0,89 0,90 0,88

30° winter 1,00 0,94 0,77 0,83 0,84 45°

30° summer 0,79 0,78 0,87 0,84 0,81

30° winter 1,00 0,94 0,69 0,74 0,74 60°

30° summer 0,78 0,66 0,78 0,75 0,71

Partial shading correction factors for horizontal surfaces shall be deduced from the geometrical configuration and the shading from the horizon as listed in Table A.1.

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A.3 Evaluation of movable solar protection devices

The effective total energy transmittance of glazing with movable solar protection devices shall be calculated using equation (108). The value of parameter a to evaluate solar protection activation depends on the orientation and surface angle of the (transparent) building surface. Tables A.4 and A.5 show values for the summer and the winter half-year, respectively. The mode of operation of the movable solar protection shall also be taken into consideration:

⎯ manually operated or timer-controlled solar protection device (see Table A.4);

⎯ solar protection device operated automatically in relation to radiation (see Table A.5).

Table A.4 — Parameter a for evaluating the effect of the activation of manually controlled or timer-controlled solar protection devices for various surface angles

a Surface angle Period

North NE/NW East/West SE/SW South

winter 0,00 0,00 0,34 0,63 0,71 vertical 90° summer 0,00 0,13 0,39 0,56 0,67

winter 0,00 0,01 0,36 0,63 0,69 60°

summer 0,03 0,33 0,54 0,68 0,76 winter 0,00 0,02 0,34 0,59 0,66

45° summer 0,30 0,46 0,61 0,72 0,78 winter 0,00 0,05 0,32 0,53 0,60

30° summer 0,55 0,60 0,67 0,74 0,78

all orientations winter 0,24 horizontal

0° summer 0,74

Table A.5 — Parameter a for evaluating the effect of activation of solar protection devices operated automatically in relation to solar radiation, for various surface angles

a Surface angle Period

North NE/NW East/West SE/SW South

winter 0,00 0,03 0,45 0,71 0,77 vertical 90 ° summer 0,10 0,49 0,70 0,77 0,79

winter 0,00 0,05 0,48 0,70 0,75 60°

summer 0,43 0,69 0,81 0,86 0,88

winter 0,01 0,08 0,47 0,67 0,72 45°

summer 0,64 0,77 0,84 0,88 0,90

winter 0,05 0,14 0,45 0,62 0,67 30°

summer 0,80 0,83 0,87 0,89 0,90

all orientations

winter 0,42 horizontal 0° summer 0,89

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Annex B (normative)

Maximum heating power in the building zone

B.1 General

The value of the maximum heating power in the building zone is required in order to calculate the utilization of the system components and hence the energy they require using the methods described in DIN V 18599-5 to DIN V 18599-9.

The maximum required heating power in a building zone is calculated by estimating the quasi-steady-state heat flows due to transmission and ventilation heat sinks for the climatic conditions of the heating season for which the system was designed. Heat sources shall be assumed to have a value of zero. Where no mechanical ventilation is installed, the value shall be determined as described in B.2.

If a mechanical ventilation system is installed, additional reheating of the supply air from the mechanical ventilation system shall be taken into consideration when calculating the utilization of the individual system components. This is discussed in B.4.

Conditioning of external air for use as supply air in mechanical ventilation systems shall not be included in the calculations of the maximum heat load. The power required for this process shall be calculated separately for VAC systems as described in DIN V 18599-3.

NOTE The maximum heating power calculated by the method described here cannot be used to substitute design load calculations for individual system components using the applicable standards.

B.2 Calculation of the maximum heating power Q⋅h,max for a design reference day

(without mechanical ventilation)

Q⋅h,max = Q⋅sink,max = Q⋅

T,max + Q⋅V,max (B.1)

with

Q⋅T,max = ∑j

jHT, (ϑi,h,min – ϑj,h,min) (B.2)

Q⋅V,max = ∑j

kH V, (ϑi,h,min – ϑk,h,min) (B.3)

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where

Hj is the heat transfer coefficient for transmission to an adjacent area j (HD according to 6.2.1, HT,iu according to 6.2.2 or HT,iz according to 6.2.3, HT,s according to

6.2.4);

HV,k is the heat transfer coefficient for ventilation mode k (HV,inf according to 6.3.1, HV,win according to 6.3.2, HV,z according to 6.3.5; air change rates

shall be determined on the basis of the usage-dependent air change, i.e. without mechanical ventilation or with mechanical ventilation switched off);

ϑi,h,min is the design internal temperature for heating as specified in DIN V 18599-10 (in the absence of specific data, ϑi,h,min = 20 °C shall be assumed);

ϑj,h,min and ϑk,h,min are the temperatures of an adjacent area or an air flow from an adjacent area respectively, for design conditions. As an example:

⎯ ϑe,min is the design external temperature as specified in DIN V 18599-10;

⎯ ϑz,min is the internal temperature in an adjacent zone in the winter season assumed for design purposes as specified in DIN V 18599-10;

⎯ ϑu,h,min is the temperature in an unheated adjacent zone as calculated using equation (38), where ϑe,min and Φu = 0 (provided this was not estimated by applying temperature correction factors).

B.3 Design conditions

The following boundary conditions shall be taken into consideration:

⎯ climatic conditions (ϑe,min) on the day taken as a design reference day for heating are to be as specified in DIN V 18599-10;

⎯ internal heat gains and solar heat gains are to be assumed to be zero;

⎯ reduced heating at night-time is to be neglected;

⎯ the air volume flow values (infiltration and window airing) applying to normal usage times are to be applied (see DIN V 18599-10);

⎯ heat and cold gains due to heat generation and refrigeration, storage and distribution processes are to be neglected.

B.4 Maximum heating power, taking into consideration a mechanical ventilation system

To take a mechanical ventilation system into consideration when determining the maximum heating power required in a building zone, the calculations shall take into account cold gains due to the supply air induced by the mechanical ventilation system. In this case, the calculations shall include the volume flow of the ventilation system for winter design conditions and corresponding to the type of usage and/or the requirements of the system, as well as the supply air temperature under design conditions. The ventilation system shall be taken into consideration when determining values for infiltration and air change due to window airing.

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The required heating power, including the power required for reheating supply air, shall thus be calculated as follows:

V,mech,minV,maxT,maxsink,maxh,max,res QQQQQ &&&&& ++−= (B.4)

with

( )∑ −=j

jjHQ ,h,mini,h,minT,T,max ϑϑ& (B.5)

( )∑ −=j

kkHQ ,h,mini,h,minV,V,max ϑϑ& (B.6)

( )V,mechi,h,minaap,mech,minV,mech,min ϑϑ −== PcVQ && , in cases where ϑi,h,min > ϑV,mech (B.7)

where

Hj is the heat transfer coefficient for transmission to an adjacent area j (HD according to 6.2.1, HT,iu according to 6.2.2 or HT,iz according to 6.2.3, HT,s according to 6.2.4);

HV,k is the heat transfer coefficient for ventilation mode k (HV,inf according to 6.3.1, HV,win according to 6.3.2, HV,z according to 6.3.5; in each case taking the mechanical ventilation system into account according to the method used to calculate the monthly balances);

ϑi,h,min is the design internal temperature for heating as specified in DIN V 18599-10, (in the absence of specific data, ϑi,h,min = 20 °C shall be assumed);

ϑj,h,min and ϑk,h,min are the temperatures of an adjacent area or of an air flow from an adjacent area respectively, for design conditions, e.g.

⎯ ϑe,min is the external temperature for design purposes, as specified in DIN V 18599-10;

⎯ ϑz,min is the internal temperature in an adjacent zone for heating, assumed for design purposes as specified in DIN V 18599-10;

⎯ ϑu,h,min is the temperature in an unheated adjacent zone as calculated using equation (38), ϑe,min and Φu = 0 (provided this was not estimated by applying temperature correction factors);

mech,minV& is the minimum volume flow of the mechanical ventilation system under design conditions for

heating with no specific requirements, mech,bmech,min VV && = , calculated as described in 6.3.3.2;


Pa is the density of air;

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ϑV,mech is the supply air temperature of the mechanical ventilation system under design conditions for heating (as specified in DIN V 18599-7 or, in the absence of specific requirements, calculated according to 6.3.3.4, and taking into consideration the design temperature ϑe,min);

cp,a Pa shall be assigned a value of 0,34 Wh/(m3 · K).

If no mechanical ventilation system is installed, h,maxh,max,res QQ && = .

NOTE DIN V 18599-3 describes how to calculate the heating power required to condition external air for use as supply air in a mechanical ventilation system.

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Annex C (normative)

Maximum cooling power in the building zone

C.1 General

The value of the maximum cooling power required in a building zone is needed in order to:

⎯ apply the methodology described in DIN V 18599-3 to determine the type of technical building system which may be used (see C.2);

⎯ specify, depending on the type of technical building system chosen, the supply air volume flow and temperature values to be used for calculating the monthly balances as specified in DIN V 18599-3 (see C.2);

⎯ calculate the energy requirements of the system components on the basis of their utilization as described in DIN V 18599-7 (see C.2 and C.4).

The maximum cooling power required in the building zone shall be calculated using the same procedure as for calculating the monthly energy need for cooling, but assuming a different set of climatic boundary conditions; in this case it is more appropriate to determine power values.

The power requirement is calculated using an empirical equation that takes into account the sum of the contributions by heat sources and heat sinks on a design reference day, the effective heat capacity of the building zone, the operating time of the system and the permitted internal temperature variations.

Furthermore, in keeping with the definition of a cooling load according to VDI 2078 [2], the heat and cold input due to the ventilation system are neglected in the maximum cooling power calculations since the type of ventilation system to be installed cannot be determined until the maximum cooling power requirements have been calculated. The maximum cooling power for conditioning supply air shall be determined separately as described in DIN V 18599-3.

In order to calculate the power requirement (size) and utilization of (additional) cooling systems in the building zone (e.g. cooled ceilings, recooling), the cooling power required shall be calculated separately, taking the cooling energy contribution of the mechanical ventilation system into account (see C.5).

NOTE The maximum cooling power calculated by the method described here cannot be used to substitute detailed design load calculations for system components using the applicable standards or technical rules.

C.2 Calculation of the required maximum cooling power

When determining the required maximum cooling power, the following parameters shall be also be taken into

consideration based on the heat contributions Q⋅source,max and Q⋅sink,max due to heat sources and heat sinks,

respectively, on a design reference day:

⎯ The (thermal) time constant τ of the building zone;

⎯ the daily operating time tc,op,d of the system;

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⎯ the permitted internal temperature variation Δϑ.

Equation (C.1) shall be used to estimate the required maximum cooling power:

Q⋅c,max = 0,8 (Q⋅source,max – Q⋅sink,max) ( ) ⎟⎟⎠

⎞⎜⎜⎝

⎛−+−−

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛+

−1h 12

h/K 40K 2Δ

h 603,01

dop,c,

wirkwirkh 120t

CCe ϑτ

(C.1)

where

Q⋅source,max is the sum of the power of the heat sources within the considered building zone on a design reference day, calculated using equation (C.3);

Q⋅sink,max is the sum of the power of the heat sinks within the considered building zone on a design reference day, calculated using equation (C.4);

τ is the time constant of the building zone calculated as described in 6.6.2, but omitting the effect of mechanical ventilation;

Cwirk is the effective heat capacity of the building zone as specified in 6.6.1;

tc,op,d is the daily operating time of the cooling system;

Δϑ is the permitted internal temperature variation (generally 2 K).

NOTE Since, at the design conditions, Q⋅source,max >> Q⋅

sink,max, the following simplified expression can be assumed for the utilization factor as a function of the ratio of heat sources to heat sinks under design conditions:

maxsource,

maxsink,1QQ&

&=≈

γη

C.3 Design conditions

The ambient climatic data on a design reference day shall be used for calculating the balance of heat sources and heat sinks. These data are specified for the months July and September, according to VDI 2078.

In the above,

ϑe,max is the daily average external temperature on the design reference day (see DIN V 18599-10:2007-02, Table 7);

IS,max is the maximum hourly solar irradiance on the design reference day (daily average as specified in DIN V 18599-10:2005-07, Table 7).

In this case, the values for the month in which the higher Q⋅c,max value is obtained shall be used. If this cannot be determined definitely, the calculation may have to be repeated for both months, i.e. July and September.

The internal temperature ϑ i,c,max,d to be assumed in the design balance calculations is the daily average, obtained from the mean set-point temperature and the maximum permitted internal temperature in equation (C.2).

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ϑi,c,max,d 2

K 2sollc,i,c,maxi, −+=

ϑϑ (C.2)

where

ϑi,c,max is the maximum temperature (maximum permitted internal temperature on a design reference day) as specified in DIN V 18599-10;

ϑi,c,soll is the internal set-point temperature for cooling as specified in DIN V 18599-10.

Further assumptions to be applied:

⎯ solar protection devices are assumed to be active (to be calculated as permanent solar protection);

⎯ mechanical ventilation effects are neglected (Hv,mech = 0);

⎯ the air change rate nwin due to window airing is assumed to be 0,1 h–1;

⎯ heat and cold gains due to heat generation and cold generation, storage and distribution shall be neglected.

C.4 Calculation of heat sources and sinks under design conditions

All heat flows taken into account when calculating the monthly energy balance shall be taken into consideration here too, except for the effects of mechanical ventilation and the sources and sinks due to distribution and generation, which can only be determined after the initial design specification calculations have been concluded.

Q⋅source,max = Q⋅S + Q⋅T + Q⋅V + Q⋅ I,source (C.3)

where

Q⋅S is the sum of flows resulting from heat sources due to solar radiation calculated using equations (C.18) to (C.21);

Q⋅T is the sum of flows due to transmission heat sources for cases where ϑi,c,max,d < ϑe,max, calculated using equations (C.6), (C.8) or (C.9), (C.11);

Q⋅V is the sum of flows due to ventilation heat sources for cases where ϑi,c,max,d < ϑe,max, calculated using equations (C.13) and (C.15);

Q⋅ I,source is the sum of flows due to internal heat sources calculated using equation (C.23).

Q⋅sink,max = Q⋅T + Q⋅

V + Q⋅ I,sink (C.4)

where

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Q⋅T is the sum of flows due to transmission heat sinks for cases where ϑi,c,max,d > ϑe,max, calculated using equations (C.5), (C.7) and (C.10);

Q⋅V is the sum of flows due to ventilation heat sinks for cases where ϑi,c,max,d > ϑe,max, calculated using equations (C.12) and (C.14);

Q⋅ I,sink is the sum of flows due to internal heat sinks calculated using equation (C.24).

The individual heat flows are calculated as specified in C.4.1 to C.4.12.

C.4.1 Heat transmission to the external environment

Q⋅T,e = HT,D (ϑi – ϑe,max) for ϑi > ϑe,max (heat sink) (C.5)

Q⋅T,e = HT,D (ϑe,max – ϑi) for ϑi < ϑe,max (heat source) (C.6)

where

HT,D is the heat transfer coefficient of transmission between the considered building zone and the external environment, calculated as specified in 6.2.1;

ϑi is the internal temperature ϑi,c,max,d assumed for design conditions, calculated using equation (C.2);

ϑe,max is the mean external temperature on a design reference day as specified in DIN V 18599-10;

C.4.2 Heat transmission through the ground

Q⋅T,s = HT,s (ϑi – ϑe,max) for ϑi > ϑe,max (heat sink) (C.7)

Q⋅T,s = HT,s (ϑe,max – ϑi) for ϑi < ϑe,max (heat source) (C.8)

or, for buildings with significant heat losses through the ground (see 6.2.4).

Q⋅T,s = ΦG (see DIN EN ISO 13370) (C.9)

where

HT,s is the heat transfer coefficient of transmission through the ground as specified in 6.2.4;


ϑe,max is the mean external temperature on a design reference day according to DIN V 18599-10.

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C.4.3 Other transmission heat flows

Q⋅T,j = HT,j (ϑi – ϑj) for ϑi > ϑj (heat sink) (C.10)

Q⋅T,j = HT,j (ϑj – ϑi) for ϑi < ϑj (heat source) (C.11)

where

HT,j is the heat transfer coefficient of transmission between the considered building zone and an adjacent zone or area (HT,iu according to 6.2.2 or HT,iz according to 6.2.3);


ϑj is the mean temperature of the adjacent area under design conditions (ϑu as described in 6.1.3 or ϑz calculated using equation (C.2)) (also applies to zones without cooling).

C.4.4 Heat flows due to infiltration

Q⋅V,inf = HV,inf (ϑi – ϑe,max) for ϑi > ϑe,max (heat sink) (C.12)

Q⋅V,inf = HV,inf (ϑe,max – ϑi) for ϑi < ϑe,max (heat source) (C.13)

where

HV,inf is the infiltration heat transfer coefficient as specified in 6.3.1 (without mechanical ventilation);


ϑe,max is the mean external temperature on a design reference day as specified in DIN V 18599-10.

C.4.5 Heat flows due to window airing

Q⋅V,win = HV,win (ϑi – ϑe,max) für ϑi > ϑe,max (heat sink) (C.14)

Q⋅V,win = HV,win (ϑe,max – ϑi) für ϑi < ϑe,max (heat source) (C.15)

where

HV,win is the heat transfer coefficient of window airing as specified in 6.3.2 (assuming that the air change rate due to window airing nwin = 0,1 h–1);


ϑe,max is the mean external temperature on a design reference day as specified in DIN V 18599-10.

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C.4.6 Heat flows due to supply air from a mechanical ventilation system

The heat flows due to supply air from mechanical ventilation systems are not included in the balances here, but shall be determined after the design specification balance has been calculated.

C.4.7 Heat flows due to air entering from adjacent zones

The heat flows due to air entering from an adjacent zone only have to be taken into consideration if the temperature difference between the internal set-point temperatures exceeds 4 K. The air change rate shall be calculated without taking mechanical ventilation systems into consideration.

Q⋅V,z = HV,z (ϑi – ϑz) for ϑi < ϑz (heat sink) (C.16)

Q⋅V,z = HV,z (ϑz – ϑi) for ϑi < ϑs (heat source) (C.17)

where

HV,z is the heat transfer coefficient of air exchange with other zones as specified in 6.3.5, neglecting mechanical ventilation;


ϑz is the internal temperature of the adjacent zone under design conditions for cooling, calculated using equation (C.2) (also applies to zones without cooling).

C.4.8 Solar heat gains via transparent building elements

trS,Q& = A FF FV gtot IS,max (C.18)

where

IS,max is the maximum hourly solar irradiance on a design reference day (see DIN V 18599-10);

A is the area of the transparent building element;

FF is the frame factor, which corresponds to the ratio of the transparent area to the total area of the glazed element. In the absence of more precise data, FF shall be assumed to be equal to 0,7;


gtot is the total energy transmittance including solar protection (as described in 6.4.1).

If gtot IS,max < g⊥ IS,max,dif, then g⊥ IS,max,dif shall be used in (C.18) instead of gtot IS,max. IS,max,dif is the minimum value of the diffuse solar irradiance on a design reference day when there is no direct incidence of solar radiation on the considered surface. For July, IS,max,dif = 139 W/m2, and for September IS,max,dif = 108 W/m2.

C.4.9 Solar heat gains via opaque elements

opS,Q& = Rse U A (α IS,max – Ff hr Δϑer) (C.19)

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where

Rse is the external surface resistance;

U is the thermal transmittance of the element;


α is the solar radiation absorption coefficient of the element;

IS,max is the maximum hourly solar irradiance on a design reference day (see DIN V 18599-10);

Ff is the form factor for the relationship between the building element and the sky: Ff = 1 for horizontal elements and elements sloping by up to 45°; Ff = 0,5 for vertical elements and elements sloping by more than 45°;

hr is the external radiative heat transfer coefficient;

Δϑer is the mean difference between the temperature of the ambient atmosphere and the apparent sky temperature; for simplified calculations Δϑer can be assumed to be 10 K.

(Reference shall also be made to 6.4.2.)

NOTE Heat sinks due to radiation in combination with opaque building elements are not of relevance in the design calculations.

C.4.10 Solar heat gains via building elements with transparent thermal insulation

TIS,Q& = Re U A FF gTI α IS,max (C.20)

where

Re is the external thermal resistance of the building element (calculated in an outward direction, starting from the absorbent layer; thermal resistance of the transparent insulation including the external surface resistance);

U is the total thermal transmittance of the element;

A is the total area of the element with transparent insulation in a specific orientation;

FF is the frame factor;

gTI is the total energy transmittance of the transparent thermal insulation, as certified;

α is the solar radiation absorption coefficient of the transparent thermal insulation;

IS,max is the maximum hourly solar irradiance on a design reference day (see DIN V 18599-10).

(Reference shall also be made to 6.4.2.)

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C.4.11 Solar heat gains via unheated sunspaces (glazed annexes)

trS,Q& FF,iu Aiu FV gtot,iu FF,ue τe,ue IS,max (C.21)

where

FF,iu is the frame factor to account for the proportion of frame on the internal glazing. In the absence of more precise data, FF,iu shall be assumed to be 0,7;

Aiu is the area of the the component of the partition between the building zone being considered and the unheated sunspace (using the clear unfinished dimensions);


gtot,iu is the total energy transmittance, including solar protection (as described in 6.4.1);

FF,ue is the frame factor to account for the proportion of frame on the external glazing. In the absence of more precise data, FF,ue shall be assumed to be 0,9;

τe,ue is the transmittance of the external glazing (see Table 5 for default values);


The thermal flow into the sunspace shall be calculated using equation (115). The solar radiation entering the sunspace shall be calculated using equation (C.22):

ΦS,u = FF,ue Aue FV gtot,ue IS,max (C.22)

where

FF,ue is the frame factor to account for the proportion of frame on the external glazing. In the absence of more precise data, FF,ue shall be assumed to be 0,9;

Aue is the area of external elements of the sunspace with a specific orientation;


gtot,ue is the total energy transmittance including solar protection (as described in 6.4.1);


C.4.12 Internal heat sources and heat sinks

Internal heat sources and sinks shall be calculated as described in 6.5. The mean daily values shall be converted to the mean heat flows (mean heating power) during the operating time.

hI,goodsI,facI,LI,pI,sourceI, QQQQQQ &&&&&& ++++= (C.23)

and

csink,I,goodssink,I,facsink,I,sinkI, QQQQ &&&& ++= (C.24)

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with

dop,c,

BPI,PI, t

AqQ =& (C.25)

dop,c,

BfacI,facI,facsink,I, or

tAq

QQ =&& (C.26)

dop,c,

elektrL,I,LLI, t

QQ

μ=& (C.27)

dop,c,

outingoodsI,

)(t

mcQ

ϑϑ −=

&& for ϑin > ϑout (C.28)

dop,c,

inoutgoodssink,I,

)(t

mcQ

ϑϑ −=

&& for ϑin < ϑout (C.29)

source,hI,Q& = 0 (C.30)

csink,I,Q& = 0 (C.31)

where

tc,op,d is the daily operating time of the cooling system.

(See 6.5 for definitions of the variables.)

NOTE For the purpose of the design specification balance calculations, the heat sources and sinks due to distribution pipes and air ducts shall be assumed to be zero, as these values can only be determined in a subsequent calculation step.

C.5 Cooling power required in a building zone equipped with a mechanical ventilation system

To calculate the required cooling power of additional system elements for recooling in the building zone, the cooling energy contribution due to the supply air from the mechanical ventilation system shall be subtracted from the maximum required cooling power c,maxQ& . Where applicable, the air entering or extracted from an adjacent zone by the mechanical ventilation system shall also be taken into account.

This is calculated as follows:

)( mechV,dmax,c,i,aap,maxmech,maxc,resmax,c, ϑϑ −−= PcVQQ &&& (C.32)

where

c,maxQ& is the maximum required cooling power according to equation (C.1);

ϑi,c,max,d is the internal temperature assumed for design conditions, according to equation (C.2);

ϑV,mech is the supply air temperature of the mechanical ventilation system under design conditions for cooling (as specified in DIN V 18599-7 or, in the absence of specific requirements, calculated according to 6.3.3.4, whereby the design temperature ϑz of adjacent zones is to

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be taken into consideration if air flows from the adjacent zones into the zone being evaluated);

V⋅mech,max is the maximum air volume flow of the mechanical ventilation system, i.e.:

⎯ bmech,V& for constant air volume systems;

⎯ mech,max,mV& for variable air volume systems according to DIN V 18599-3;

⎯ if the ventilation is in the form of intentional air exchange between several zones, the air volume flow zV& under design conditions (see 6.3.5);

cp,a is the specific heat capacity of air.

Pa is the density of air.

cp,a Pa shall be assigned a value of 0,34 Wh/(m3 · K).

If no mechanical ventilation system is installed, c,maxh,max,res QQ && = .

NOTE DIN V 18599-3 describes how to calculate the cooling power required to condition external air for use as supply air in a mechanical ventilation system.

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Annex D (normative)

Calculation of monthly heating and cooling times

D.1 General

SInce the beginning and end of the operating periods of heating and cooling systems which are not operated all year round do not generally coincide with the beginning and end of a month, the heating or cooling times in transitional months needs to be calculated. The heating and cooling times are required in DIN V 18599-5 to DIN V 18599-7in order to determine the mean part load.

D.2 Monthly heating time

The heating time shall be calculated separately for the days on which the zone is used and those on which it is not used in each month. The monthly heating time is the sum of the heating times of days on which the zone is used and those on which it is not used.

th = th,nutz + th,we (D.1)

The heating time for a usage profile shall be calculated using equation (D.2):

⎪⎩

⎪⎨

⎧

>

≤=

grenzh,h,mth,

grenzh,h,grenzh,

h,mth,

h,for

for

ββ

βββ

β

ii

ii

ii

t

tt (D.2)

where βh,i is

h24h,max,res

h,b,nutzh,nutz Q

Q&

=β or h24h,max,res

weh,b,weh, Q

Q&

=β (D.3)

and tmth,i is:

tmth,nutz = dnutz 24 h or tmth,we = dwe 24 h (D.4)

The following shall be assumed for the minimum utilization:

βh,grenz = 0,05

where

th,i is the heating time during a period of normal usage (th,nutz), or a period with weekend or holiday operation (th,we), respectively;

tmth,i is the total time of normal usage (tmth,nutz), or the total time with weekend or holiday operation (tmth,we) respectively, within the month;

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βh,i is the mean utilization of the heating system during periods of normal usage (bh,op), or periods with weekend or holiday operation (βh,we), respectively, during the month;

βh,grenz is the minimum utilization of the heating system;

Qh,b,nutz is the balanced energy need of the building zone for heating under normal usage conditions (daily value);

Qh,b,we is the balanced energy need of the building zone for heating when the heating is operated in weekend or holiday mode (daily value);

h,max,resQ& is the maximum heating power required in the building zone as specified in Annex B;

dnutz is the number of days of normal usage in the month;

dwe is the number of days of the month without usage or with reduced usage (e.g. weekends, holidays).

D.3 Monthly cooling time

The cooling time shall be calculated separately for the days on which the zone is used and those on which it is not used in each respective month. The monthly cooling time is the sum of the cooling times of days on which the zone is used and of those on which it is not used.

tc = tc,nutz + tc,we (D.5)

The cooling time for a usage profile shall be calculated using equation (D.6):

⎪⎩

⎪⎨

⎧

>

≤=

grenzc,c,mth,

grenzc,c,grenzc,

c,mth,

c,for

for

ββ

βββ

β

ii

ii

ii

t

tt (D.6)

where βc,i is equal to:

nutzop,c,resmax,c,

nutzb,c,nutzc, tQ

Q&

=β or weop,c,resmax,c,

web,c,wec, tQ

Q&

=β (D.7)

and tmth,i:

tmth,nutz = dnutz tc,op,d or tmth,we = dwe tc,op,d,we (D.8)

Where no other values are specified in DIN V 18599-7, the minimum utilization shall be assumed to be

150,c,grenz =β

(i.e. seasonal operation).

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where

tc,i is the cooling time during periods of normal usage (tc,nutz), or during periods of weekend or holiday operation (tc,we), respectively;

tmth,i is the total time of normal usage (tmth,nutz), or the total time of weekend or holiday operation (tmth,we), respectively, within the month;

βc,i is the mean utilization of the cooling system during periods of normal usage (βc,nutz), or during periods of weekend or holiday operation (βc,we), respectively, for the month;

βc,grenz is the minimum usage of the cooling system;

Qc,b,nutz is the balanced energy need of the building zone for cooling under normal usage conditions (daily value);

Qc,b,we is the balanced energy need of the building zone for cooling when in weekend or holiday operation (daily value);

resmax,c,Q& is the maximum cooling power required in the building zone (as specified in Annex C);

dnutz is the number of days of normal usage in the month;

dwe is the number of days of the month without usage or with reduced usage (e.g. weekends, holidays);

tc,op,d is the daily operating time of the cooling system as specified in DIN V 18599-10;

tc,op,d,we is the daily operating time of the cooling system for days with limited usage. For the types of usage given in DIN V 18599-10, tc,op,d,we = 0 applies.

NOTE Generally, the cooling system operating time is equal to the ventilation system operating time. If the cooling system in the building zone is operated at times when the ventilation is not in operation (e.g. in cooling systems with heat transfer via building elements), tc,op,d shall be assumed to be 24 h.

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Annex E (informative)

Default values of volume flow of HVAC systems

E.1 General

The supply air temperature and the volume flow of the system need to be known in order to determine the heat sources or heat sinks due to the supply air from a mechanical ventilation system. If no specific values are available at the preliminary planning stage, the default volume flow values listed here can be used as initial estimates for conventional air conditioning systems. Default values of supply air temperatures are listed in DIN V 18599-7.

The default values are not a substitute for detailed professional planning of a ventilation system. Once the air volume flows have been specified for the project design, these are to be used in the energy balance calculations.

The ventilation system shall ensure that thermal comfort as specified in DIN EN 13779 is maintained.

E.2 Default values for the permissible volume flow

Figure E.1 illustrates the relationship between the maximum cooling power and the permitted volume flow as a function of the type of air conditioning system used. The specific cooling power and volume flow are specified in relation to the reference area AB. For variable air volume systems, mechV& corresponds to the maximum

possible volume flow maxmech,V& (see DIN V 18599-3); for other types of air conditioning system,

mechV& corresponds to the reference volume flow bmech,V& .

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Figure E.1 — Relationship between the maximum cooling power and the permitted volume flow as a function of the type of air conditioning system

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Bibliography

[1] Loga, Kahlert, Laidig, Lude: Räumlich und zeitlich eingeschränkte Beheizung (Spatially and time-relatedly reduced heating), Institut Wohnen und Umwelt; December 1999

[2] VDI 2078, Cooling load calculation of air-conditioned rooms (VDI cooling load regulations)

[3] Bestimmung des solaren Energiegewinns durch Massivwände mit transparenter Wärmedämmung (Determination of solar energy gains through solid walls with transparent thermal insulation) Fachverband Transparente Wärmedämmung e. V. (Association of transparent thermal insulation), Gundelfingen i. Br. (2000)

DIN 277-1, Areas and volumes of buildings — Part 1: Terminology, bases of calculation

DIN 410, Glass in building — Determination of luminous and solar characteristics of glazing

DIN 4108 Supplement 2, Thermal insulation and energy economy in buildings — Thermal bridges — Examples for planning and performance

DIN V 4108-2, Thermal insulation and energy economy in buildings — Part 2: Minimum requirements to thermal insulation

DIN EN 673, Glass in building — Determination of thermal transmittance (U-value) — Calculation method

DIN EN 674, Glass in building — Determination of the thermal transmittance (U-value) — Guarded hot plate method

DIN EN 675, Glass in building — Determination of the thermal transmittance (U-value) — Heat flow meter method

DIN EN 12524, Building materials and products — Hygrothermal properties — Tabulated design values

DIN EN 13779, Ventilation for non-residential buildings — Performance requirements for ventilation and room-conditioning systems

DIN EN 13829, Thermal performance of buildings — Determination of air permeability of buildings — Fan pressurization method

E DIN EN ISO 10077-2, Thermal performance of windows, doors and shutters — Calculation of thermal transmittance –Part 2: Numerical method for frames

DIN EN ISO 12567-1, Thermal performance of windows, doors and shutters — Determination of thermal transmittance by hot box method — Part 1: Complete windows and doors

E DIN EN ISO 12567-2, Thermal performance of windows, doors and shutters — Determination of thermal transmittance by hot box method — Part 2: Roof windows and other projecting windows

DIN EN ISO 14683, Thermal bridges in building construction — Linear thermal transmittance — Simplified methods and default values

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