DIN V Date: 2007 February

Transcription

1 Date: 2007 February DIN V 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 :

2 Contents Page Foreword...6 Introduction Scope Normative references Terms and definitions, symbols and units Terms and definitions Symbols, units and subscripts Relationship between the parts of the DIN V series of prestandards Input parameters from other parts of the DIN V series of prestandards Output parameters for other parts of the DIN V series of prestandards Determination of the energy use for various types of technical building systems according to the DIN V series of prestandards Monthly balance calculation method Principle of balance calculation method Balance boundaries and calculation period Heat sources and heat sinks Utilization of heat sources and heat sinks Factors affecting the heat sources and heat sinks Balance equations for calculating the energy needs of a building zone for heating and cooling General Balance equations for calculating the energy need for heating Balance equations for calculating the energy need for cooling Accounting for weekend and holiday-period operation Balance of the energy need for heating Balance of the energy need for cooling Monthly values and annual values Heat sinks General Transmission heat sinks Ventilation heat sinks Internal heat sinks Heat sinks due to radiative heat transfer Heat storage Heat sources General Heat sources due to solar radiation Transmission heat sources Ventilation heat sources Internal heat sources Utilization of the heat sources General (Thermal) time constant of the building zone Utilization factor Determination of individual parameters for the monthly balance Room temperature assumptions Reference internal temperature for calculating the energy need for heating Reduced heating at night Reduced heating operation during weekends and holiday periods

3 Partial heating (spatially reduced heating operation) Combination of partial heating and reduced heating Reference internal temperature for cooling Temperature of an adjacent unheated or uncooled zone General Approximate method using temperature correction factors to determine the mean temperatures in unheated zones Detailed calculation of the temperature in an unheated or uncooled building zone Temperature of an adjacent heated or cooled zone Transmission heat sinks/heat sources Direct transmission to the external environment Calculation of the heat sinks and sources due to transmission to the external environment Calculation of coefficients of heat transfer to the external environment (assuming a standard allowance for thermal bridges) Calculation of coefficients of heat transfer to the external environment (using linear thermal transmittance) Transmission through unheated or uncooled spaces to the external environment Transmission to adjacent heated or cooled building zones Transmission through the ground Ventilation heat sinks/sources Infiltration Determination of the infiltration air change rate Evaluation of infiltration of zones with mechanical ventilation systems Window airing Determination of air change rate due to window airing Usage-dependent minimum air exchange with external air Mechanical ventilation Determination of the mean air change rate due to ventilation systems Air change due to supply air from mechanical ventilation systems Extract air change due to mechanical ventilation systems Supply air temperature of mechanical ventilation Note on the evaluation of ventilation systems with extract air/supply air heat exchangers for use in residential buildings Ventilation in unheated or uncooled building zones Air exchange between building zones Supply air change rate from adjacent building zones Extract air change rate into adjacent zones Radiation heat sources and sinks Heat sources due to solar radiation entering through transparent surfaces Solar heat gains via opaque building elements Solar heat gains via unheated or uncooled sunspaces (glazed annexes) Direct solar heat gains in the building zone Heat gains affecting the unheated or uncooled sunspace (glazed annex) Calculation of balances for glass double façades Internal heat sources and sources of cold Internal heat sources in residential buildings

4 6.5.2 Heat sources due to persons Heat sources and sinks due to machinery and equipment Internal heat sources/heat sinks due to movement of materials Heat sources due to artificial lighting Heat sources and sinks due to heating, cooling, domestic hot water supply and ventilation systems Taking into account stored heat between days of usage and non-usage Utilization factors of heat sources Effective heat capacity (thermal mass) (Thermal) time constant Utilization factor Limits for the utilization factor Annex A (normative) Shading factors and movable solar protection devices A.1 General A.2 Correction factors for external shading A.3 Evaluation of movable solar protection devices Annex B (normative) Maximum heating power in the building zone B.1 General B.2 Calculation of the maximum heating power Q h,max for a design reference day (without mechanical ventilation) B.3 Design conditions B.4 Maximum heating power, taking into consideration a mechanical ventilation system Annex C (normative) Maximum cooling power in the building zone C.1 General C.2 Calculation of the required maximum cooling power C.3 Design conditions C.4 Calculation of heat sources and sinks under design conditions C.4.1 Heat transmission to the external environment C.4.2 Heat transmission through the ground C.4.3 Other transmission heat flows C.4.4 Heat flows due to infiltration C.4.5 Heat flows due to window airing C.4.6 Heat flows due to supply air from a mechanical ventilation system C.4.7 Heat flows due to air entering from adjacent zones C.4.8 Solar heat gains via transparent building elements C.4.9 Solar heat gains via opaque elements C.4.10 Solar heat gains via building elements with transparent thermal insulation C.4.11 Solar heat gains via unheated sunspaces (glazed annexes) C.4.12 Internal heat sources and heat sinks C.5 Cooling power required in a building zone equipped with a mechanical ventilation system Annex D (normative) Calculation of monthly heating and cooling times D.1 General D.2 Monthly heating time D.3 Monthly cooling time Annex E (informative) Default values of volume flow of HVAC systems E.1 General E.2 Default values for the permissible volume flow Bibliography Figures Figure 1 Overview of the parts of DIN V Figure 2 Content and scope of DIN V (schematic diagram)

5 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 Tables Table 1 Symbols and units...13 Table 2 Subscripts...15 Table 3 Temperature correction factors for various building elements...43 Table 4 n 50 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 energyrelevant part of the solar radiation spectrum...70 Table 7 Default values for lighting heat gain coefficients µ L for air-handling luminaires...77 Table A.1 Partial shading correction factors F h for various horizon angles and surface surface angles...84 Table A.2 Partial shading correction factors F o for horizontal overhangs and various surface angles...86 Table A.3 Partial shading correction factors F f for lateral shading...88 Table A.4 Parameter a for evaluating the effect of the activation of manually operated or timeroperated 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

6 Foreword This prestandard has been prepared by DIN Joint Committee NA 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 containing a table of the data, to nabau@din.de. A template for this table is provided on the Internet under the URL or as hard-copy to Normenausschuss Bauwesen (NABau) im DIN Deutsches Institut für Normung e. V., Berlin, Germany (office address: Burggrafenstrasse 6, Berlin, Germany). The DIN V 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 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 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. 6

7 independent of the behaviour of individual users and of the local climatic data) to determine the energy needs are specified. The DIN V 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 : in that it has been revised in form and content. Previous editions DIN V :

8 Introduction When an energy balance is calculated in accordance with the DIN V 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 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

9 1 Scope The DIN V 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 DIN V 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 , 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 series of prestandards (e.g. energy gains due to artificial lighting as described in DIN V , uncontrolled heat gains due to the heating system as described in DIN V , 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. 9

10 The energy needed for heating and, 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 to DIN V 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 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 (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 , 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 , 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 10

11 DIN V , 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 , 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 , 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 , 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 , 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 , 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 , 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 , 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 , Thermal insulation and energy economy in buildings Part 4: Hygrothermal design values DIN , 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 , Thermal performance of windows, doors and shutters Calculation of thermal transmittance Part 1: General DIN EN ISO , Thermal bridges in building construction Heat flows and surface temperatures Part 1: General calculation methods DIN EN ISO , Thermal bridges in building construction Calculation of heat flows and surface temperatures Part 2: Linear thermal bridges DIN EN , Solar protection devices combined with glazing Calculation of solar and light transmittance Part 1: Simplified method 11

12 DIN EN , Solar protection devices combined with glazing Calculation of solar and light transmittance Part 2: Detailed calculation method DIN EN ISO 13370: , Thermal performance of buildings Heat transfer via the ground Calculation methods E DIN EN ISO 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 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 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) 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) 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 12

13 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 A B Reference area m 2 c C wirk Specific heat capacity Effective heat capacity of a building zone kj/(kg K), Wh/(kg K) kj/k, (W h)/k d mth Number of days in the month d/mth d nutz (Mean) number of usage days in the month d/mth d we (Mean) number of days with weekend or holiday period operation in the month d/mth e wind Wind shielding coefficient f NA f tb Correction factor to account for reduced heating operation at night time Correction factor to account for reduced heating operation in certain spaces f V,mech Factor for evaluating infiltration in the case of mechanical ventilation f wind Wind shielding coefficient f we Correction factor to account for reduced heating operation over several days F Factor F f Radiation-effective form factor between element and sky, or partial shading correction factor for fins F F Frame factor F S Shading coefficient F u Temperature correction factor for elements adjacent to unheated spaces F V Dirt depreciation factor F w Correction factor to account for oblique incidence of solar radiation F x Temperature correction factor for element type x g eff Effective total energy transmittance g tot Total energy transmittance taking into account solar protection devices g Total energy transmittance for perpendicular incidence of solar radiation h r External radiative heat transfer coefficient W/(m 2 K) 13

14 Symbol Table 1 (continued) Meaning Common unit H Heat transfer coefficient, general W/K H T Transmission heat transfer coefficient for the entire building zone W/K H T,D Heat transfer coefficient for transmission between the heated building zone and external air H T,s Heat transfer coefficient for transmission through the ground W/K H V Ventilation heat transfer coefficient W/K H V,inf Infiltration heat transfer coefficient W/K H V,win Heat transfer coefficient for window airing W/K H V,mech Heat transfer coefficient for mechanical ventilation W/K H V,mech,ϑ Temperature-weighted heat transfer coefficient for mechanical ventilation W/K I s 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 n 50 Air change rate at a pressure difference of 50 Pa h 1 Q Heat, quantity of heat according to DIN EN ISO 7345 W/K Wh, kwh Wh/a, kwh/a Q & Mean heating power W, kw Q sink Heat sinks Wh, kwh Q source Heat sources Wh, kwh Q S Solar heat gains, radiation heat Wh, kwh Q I Internal thermal gains (heat or cold) Wh, kwh Q h,b Balanced energy need for heating of the building zone Wh, kwh Q c,b Balanced energy need for cooling of the building zone Wh, kwh Q S,tr Solar heat gains from transparent surfaces Wh Q S,op Solar heat gains/losses by/from opaque surfaces Wh R Thermal resistance, surface resistance (m 2 K)/W t Time, time period h t V,mech Daily operating time of the mechanical ventilation system h U Thermal transmittance W/(m 2 K) V Net volume of the space (ventilated volume) m 3 V Volume flow m 3 /s, m 3 /h α Absorption coefficient for solar radiation (opaque surfaces) α sp Solar radiation absorption coefficient of the partition between the unheated sunspace and the core building 14

15 Symbol Table 1 (continued) Meaning Common unit ϑ e External air temperature C ϑ i Reference internal temperature C ϑ i,c,soll Internal set-point temperature for cooling during periods of use ( usage periods ) ϑ i,h,soll Internal set-point temperature for cooling during usage periods C ϑ V,mech Supply air temperature of a mechanical ventilation system C ϑ u Air temperature in an unheated or uncooled zone C ϑ z Reference internal temperature of an adjacent heated or cooled zone Δϑ er Difference between the external air temperature and sky temperature K λ Thermal conductivity W/(m K) η η V,mech Utilization factor 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 τ e Radiation transmittance ρ e Radiation reflectance ρ Density; bulk density kg/m3 Table 2 Subscripts C Index a a ABL b B c C e eff elektr Meaning Year (annum), e.g. 1/a = annual Air Extract air (of a mechanical ventilation system) Net energy (as in energy need ) Solar protection device (e.g. blind) Cooling Relating to heat storage External, or from a specified layer outwards to the ambient air Effective Electrical 15

16 Index f F fac g goods h i I in inf iu L mth max mech min NA nutz op op out p Table 2 (continued) Meaning Lateral shading or with effect on radiation between a building element and the sky Frame Due to appliances, machinery and equipment Glazing Due to movement of goods (and/or materials) Space heating Internal (or from a specified layer inwards to the internal air) Internal, inside the building or space Input, entering Infiltration From a heated building zone to an unheated building zone Light Month, e. g, per month, 1/mth; mth = Jan, Feb, March, Apr, May, June, July, Aug, Sept, Oct, Nov, Dec Maximum, largest Mechanical (ventilation system) Minimum, smallest Reduced heating operation (night-time set-back) During usage hours; usage-dependent Opaque Operating, operation Output, leaving Partition between building zone and sunspace p At constant pressure (for c p,a ) P res S s sink source T tb TI tot Caused by or relating to persons, metabolic Resulting Solar, due to solar radiation Ground Heat sink Heat source Transmission Partially heated Transparent thermal insulation Total, overall 16

17 Table 2 (continued) Index tr u ue V V,mech WB win wirk we x z ZUL j,k,l Meaning Transparent Unheated or uncooled space or building zone From unheated building zone to external air (also refer to subscript e ) Ventilation Mechanical ventilation Thermal bridge Window Effective Weekend or holiday-period operating mode Represents states, elements or zones Adjacent building zone Supply air of a mechanical ventilation system Serial variables NOTE European standardized symbols and subscripts are used in Tables 1 and 2. 4 Relationship between the parts of the DIN V 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 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 series of prestandards The following are required for the balance estimates: Internal set-point temperature for heating ϑ i,h,soll see DIN V Internal set-point temperature for cooling ϑ i,c,soll see DIN V Average monthly external temperature ϑ e see DIN V Permitted internal set-back temperature for reduced operation Δϑ i,na see DIN V Ratio of indirectly heated areas to the total area α tb see DIN V

18 Minimum external air volume flow per unit area V & A see DIN V Usage dependent minimum air change rate with external air n nutz see DIN V Daily operating time of the ventilation system t V,mech see DIN V Daily operating time of the heating system t h,op,d see DIN V Number of usage days d nutz see DIN V Number of days in the month d mth see DIN V Heat dissipated by persons, appliances, machinery, equipment and lighting (residential use) q I see DIN V Heat dissipated by persons (metabolic heat) q I,p see DIN V Heat dissipated by appliances, machinery and equipment q I,fac see DIN V Mean solar irradiance for the respective month I S see DIN V Dirt depreciation factor F V see DIN V System-specific minimum supply air temperature ϑ V,mech,RLT see DIN V Supply air temperature of the ventilation system of a residential building ϑ WLA see DIN V Electrical energy for artificial lighting Q i,l,elektr see DIN V In addition, the following are needed for the final balance calculations: Uncontrolled internal heat gains due to the heating system Q I,h see DIN V Uncontrolled internal heat gains due to mechanical ventilation Q I,rv see DIN V Uncontrolled cold gains due to mechanical ventilation Q I,rv,c see DIN V Uncontrolled heat gains due to mechanical ventilation Q I,vh see DIN V Uncontrolled heat gains due to the cooling system/cold generation Q I,ch see DIN V Uncontrolled cold gains due to the cooling system (cooling and condenser water) Q I,c see DIN V Uncontrolled cold gains due to mechanical ventilation Q I,v,c see DIN V Uncontrolled heat gains due to the domestic hot water system Q I,w see DIN V

19 The following are additionally needed for the design balance calculations: Minimum internal temperature of heating operation for design calculations ϑ i,h,min see DIN V Maximum permitted internal temperature on a design reference day for cooling ϑ i,c,max see DIN V Daily mean external temperature on a design reference day for heating ϑ e,min see DIN V Daily mean external temperature on a design reference day for cooling ϑ e,max see DIN V Maximum hourly solar irradiance on a design reference day I S,max see DIN V Daily operating time of the cooling system t c,op,d see DIN V Output parameters for other parts of the DIN V series of prestandards Energy need of the building zone for heating and estimated energy need for heating Q h,b,mth DIN V DIN V DIN V Energy need of the building zone for cooling and estimated energy need for cooling Q c,b,mth DIN V DIN V DIN V Maximum heat load, maximum heating power Q h,max, Q h,max,res DIN V DIN V DIN V DIN V Maximum cooling load, maximum cooling power Q c,max, Q c,max,res DIN V DIN V Heating hours (in the respective month) t h DIN V DIN V DIN V Cooling hours (in the respective month) t c DIN V Minimum air volume flow of the mechanical ventilation system V mech,b DIN V Reference internal temperature for determining the energy need for heating ϑ i,h DIN V Reference internal temperature for determining the energy need for cooling ϑ i,c DIN V

20 Air temperature in an adjacent unheated or uncooled building zone ϑ u DIN V Determination of the energy use for various types of technical building systems according to the DIN V 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 series, depending on the type of system involved: for static (water-based) heating systems, in DIN V ; for ventilation systems for residential buildings, in DIN V ; for HVAC and cooling systems, in DIN V ; for combined heat and power (cogeneration) systems, in DIN V The energy needs for heating and cooling shall be subdivided 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 The calculations for pre-conditioning of the air in systems of this kind shall involve the handling of external air up to the point 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 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 , DIN V or DIN V , 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 ); 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 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. 20

21 5 Monthly balance calculation method 5.1 Principle of balance calculation method 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 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 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 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. 21

22 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) 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 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. 22

23 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 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 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. Q h,b = Q sink η Q source ΔQ C,b (1) Q h,b Q sink Q source ΔQ C,b is the energy need of the building zone for heating: Q h,b,nutz for usage days, and Q h,b,we for days of non-usage; is the sum of the heat sinks in the building zone under the given boundary conditions, as described in 5.3; is the sum of the heat sources in the building zone under the given boundary conditions, as described in 5.4; is the heat escaping from building elements during periods of reduced operation at weekends and during holiday periods, according to (ΔQ C,b = 0 for continuous operation); 23

24 η is the monthly utilization factor of the heat sources (for heating purposes), calculated according to 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. Q c,b = (1 η) Q source (2) Q c,b Q source is the energy need of the building zone for cooling: Q c,b,nutz for usage days and Q c,b,we for days of non-usage; 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 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)) 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: 24

25 In the balance for days with normal usage or with continuous usage: in equation (1) ΔQ C,b = ΔQ C,b,nutz = 0 and in equation (11) ΔQ C,sink = ΔQ C,sink,nutz shall be assumed as specified in 6.6. In the balance for days with weekend or holiday operation: in equation (1) ΔQ C,b = ΔQ C,b,we shall be assumed as specified in 6.6 and in equation (11) ΔQ C,sink = ΔQ C,b,we = 0 NOTE In order to determine the stored heat, the balance for the weekend should be calculated first 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: Q c,b,we = 0 (3) Transfer of heat between the days of usage and non-usage is neglected. In equation (11) ΔQ C,sink = 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: Q h,b,mth = d mth Q h,b (4) Q c,b,mth = d mth Q c,b (5) d mth Q h,b Q c,b is the number of days in the month; is the balanced energy need of the building zone for heating; 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. Q h,b,mth = d nutz Q h,b,nutz + d we Q h,b,we (6) Q c,b,mth = d nutz Q c,b,nutz + d we Q c,b,we (7) 25