ISO/TC 163/SC 2 - Calculation methods

ISO 12631:2017 specifies a method for calculating the thermal transmittance of curtain walls consisting of glazed and/or opaque panels fitted in, or connected to, frames. The calculation includes: - different types of glazing, e.g. glass or plastic; single or multiple glazing; with or without low emissivity coating; with cavities filled with air or other gases; - frames (of any material) with or without thermal breaks; - different types of opaque panels clad with metal, glass, ceramics or any other material. Thermal bridge effects at the rebate or connection between the glazed area, the frame area and the panel area are included in the calculation. The calculation does not include: - effects of solar radiation; - heat transfer caused by air leakage; - calculation of condensation; - effect of shutters; - additional heat transfer at the corners and edges of the curtain walling; - connections to the main building structure nor through fixing lugs; - curtain wall systems with integrated heating. NOTE Table 1 in the Introduction shows the relative position of ISO 12631:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 52016-1:2017 specifies calculation methods for the assessment of: a) the (sensible) energy need for heating and cooling, based on hourly or monthly calculations; b) the latent energy need for (de-)humidification, based on hourly or monthly calculations; c) the internal temperature, based on hourly calculations; d) the sensible heating and cooling load, based on hourly calculations; e) the moisture and latent heat load for (de-)humidification, based on hourly calculations; f) the design sensible heating or cooling load and design latent heat load using an hourly calculation interval; g) the conditions of the supply air to provide the necessary humidification and dehumidification. The calculation methods can be used for residential or non-residential buildings, or a part of it, referred to as "the building" or the "assessed object". ISO 52016-1:2017 also contains specifications for the assessment of thermal zones in the building or in the part of a building. The calculations are performed per thermal zone. In the calculations, the thermal zones can be assumed to be thermally coupled or not. The calculation methods have been developed for the calculation of the basic energy loads and needs, without interaction with specific technical building systems, and for the calculation of the system specific energy loads and needs, including the interaction with specific systems. The hourly calculation procedures can also be used as basis for calculations with more extensive system control options. ISO 52016-1:2017 is applicable to buildings at the design stage, to new buildings after construction and to existing buildings in the use phase. NOTE Table 1 in the Introduction shows the relative position of ISO 52016-1:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO/TR 52019-2:2017 contains information to support the correct understanding and use of ISO 6946, ISO 10211, ISO 13370, ISO 13786, ISO 13789 and ISO 14683. ISO/TR 52019-2:2017 does not contain any normative provision.

ISO 13786:2017 specifies the characteristics related to the dynamic thermal behaviour of a complete building component and provides methods for their calculation. It also specifies the information on building materials required for the use of the building component. Since the characteristics depend on the way materials are combined to form building components, ISO 13786:2017 is not applicable to building materials or to unfinished building components. The definitions given in ISO 13786:2017 are applicable to any building component. A simplified calculation method is provided for plane components consisting of plane layers of substantially homogeneous building materials. Annex C provides simpler methods for the estimation of the heat capacities in some limited cases. These methods are suitable for the determination of dynamic thermal properties required for the estimation of energy consumption. These approximations are not appropriate, however, for product characterization. NOTE Table 1 in the Introduction shows the relative position of ISO 13786:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO/TR 52016-2:2017 contains information to support the correct understanding and use of ISO 52016‑1 and ISO 52017‑1. These documents give calculation methods for the assessment of: - the (sensible and latent) energy load and need for heating and cooling, based on hourly calculations; - the (sensible and latent) energy need for heating and cooling, based on monthly calculations (ISO 52016‑1); - the internal temperature, based on hourly calculations; and - the design (sensible and latent) heating and cooling load, based on hourly calculations. ISO/TR 52016-2:2017 does not contain any normative provisions. NOTE A description of the rationale behind the reorganization of the cluster of strongly related and partly overlapping ISO and CEN standards is given in Annex H.

ISO 10077-1:2017 specifies methods for the calculation of the thermal transmittance of windows and pedestrian doors consisting of glazed and/or opaque panels fitted in a frame, with and without shutters.

ISO 52010-1:2017 specifies a calculation procedure for the conversion of climatic data for energy calculations. The main element in ISO 52010-1:2017 is the calculation of solar irradiance on a surface with arbitrary orientation and tilt. A simple method for conversion of solar irradiance to illuminance is also provided. The solar irradiance and illuminance on an arbitrary surface are applicable as input for energy and daylighting calculations, for building elements (such as roofs, facades and windows) and for components of technical building systems (such as thermal solar collectors, PV panels). Other parameters of climatic data needed to assess the thermal and moisture performance of buildings, building elements or technical building systems [like wind, temperature, moisture and long-wave (thermal) radiation] are to be obtained according to the procedures in ISO 15927‑4. These data are listed in ISO 52010-1:2017 as input and passed on as output without any conversion. NOTE 1 The reason for passing these data via ISO 52010-1:2017 is to have one single and consistent source for all EPB standards and to enable any conversion or other treatment if needed for specific application. NOTE 2 Table 1 in the Introduction shows the relative position of ISO 52010-1:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 13370:2017 provides methods of calculation of heat transfer coefficients and heat flow rates for building elements in thermal contact with the ground, including slab‐on‐ground floors, suspended floors and basements. It applies to building elements, or parts of them, below a horizontal plane in the bounding walls of the building situated - at the level of the inside floor surface, for slab‐on‐ground floors, suspended floors and unheated basements; NOTE 1 In some cases, external dimension systems define the boundary at the lower surface of the floor slab. - at the level of the external ground surface, for heated basements. ISO 13370:2017 includes calculation of the steady‐state part of the heat transfer (the annual average rate of heat flow) and the part due to annual periodic variations in temperature (the seasonal variations of the heat flow rate about the annual average). These seasonal variations are obtained on a monthly basis and, except for the application to dynamic simulation programmes in Annex D, ISO 13370:2017 does not apply to shorter periods of time. NOTE 2 Table 1 in the Introduction shows the relative position of ISO 13370:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 13789:2017 specifies a method and provides conventions for the calculation of the steady‐state transmission and ventilation heat transfer coefficients of whole buildings and parts of buildings. It is applicable both to heat loss (internal temperature higher than external temperature) and to heat gain (internal temperature lower than external temperature). For the purpose of ISO 13789:2017, the heated or cooled space is assumed to be at uniform temperature. Annex C provides a steady‐state method to calculate the temperature in unconditioned spaces adjacent to conditioned spaces. NOTE Table 1 in the Introduction shows the relative position of ISO 13789:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 6946:2017 provides the method of calculation of the thermal resistance and thermal transmittance of building components and building elements, excluding doors, windows and other glazed units, curtain walling, components which involve heat transfer to the ground, and components through which air is designed to permeate. The calculation method is based on the appropriate design thermal conductivities or design thermal resistances of the materials and products for the application concerned. The method applies to components and elements consisting of thermally homogeneous layers (which can include air layers). ISO 6946:2017 also provides an approximate method that can be used for elements containing inhomogeneous layers, including the effect of metal fasteners, by means of a correction term given in Annex F. Other cases where insulation is bridged by metal are outside the scope of ISO 6946:2017. NOTE Table 1 in the Introduction shows the relative position of ISO 6946:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000‑1.

The set of EPB assessment standards produces a great number of overall and partial EPB indicators as outputs, which can be used for different purposes. ISO 52018-1:2017 deals with the use as requirement of partial EPB indicators related to the fabric and related to the thermal balance of the building. Thermal balance aspects concern both the heating and cooling needs and the free floating temperatures, especially with respect to overheating or too cold indoor temperatures. ISO 52018-1:2017 can support both private parties and public regulators (and all stakeholders involved in the regulatory process) with the "post-processing" of these outputs. ISO 52018-1:2017 provides standardized tables for reporting, in a structured and transparent manner, the choices that are to be made with respect to the partial EPB requirements covered by ISO 52018-1:2017. The tables are non-restrictive, thus allowing for full regulatory flexibility. NOTE Table 1 in the Introduction shows the relative position of ISO 52018-1:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 10211:2017 sets out the specifications for a three-dimensional and a two-dimensional geometrical model of a thermal bridge for the numerical calculation of - heat flows, in order to assess the overall heat loss from a building or part of it, and - minimum surface temperatures, in order to assess the risk of surface condensation. These specifications include the geometrical boundaries and subdivisions of the model, the thermal boundary conditions, and the thermal values and relationships to be used. ISO 10211:2017 is based upon the following assumptions: - all physical properties are independent of temperature; - there are no heat sources within the building element. ISO 10211:2017 can also be used for the derivation of linear and point thermal transmittances and of surface temperature factors. NOTE Table 1 in the Introduction shows the relative position of ISO 10211:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO/TR 52022-2:2017 contains information to support the correct understanding and use of ISO 10077‑1, ISO 10077‑2, ISO 12631, ISO 52022‑1 and ISO 52022‑3. This technical report does not contain any normative provision.

ISO 52017-1:2017 specifies the general assumptions, boundary conditions and equations for the calculation, under transient hourly or subhourly conditions, of the internal temperatures (air and operative) and/or the heating, cooling and humidification and dehumidification loads to hold a specific (temperature, moisture) set point, in a single building zone. No specific numerical techniques are imposed by ISO 52017-1:2017. Specific calculation procedures based on the generic calculation procedures of ISO 52017-1:2017 are given in ISO 52016-1. The specific simplifications, assumptions and boundary conditions in ISO 52016-1 are tailored to the respective application areas, such as the energy need for heating and cooling and for humidification and dehumidification, hourly internal temperature, design heating and cooling and humidification and dehumidification load. NOTE Table 1 in the Introduction shows the relative position of ISO 52017-1:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 52022-1:2017 specifies a simplified method based on thermal, solar and light characteristics of the glazing and solar and light characteristics of the solar protection device, to estimate the total solar energy transmittance, direct energy transmittance and the light transmittance of a solar protection device combined to a glazing.

ISO/TR 52018-2:2017 refers to ISO 52018‑1. ISO 52018‑1 gives a succinct enumeration of possible requirements related to thermal energy balance features and to fabric features. It also provides tables for regulators to report their choices in a uniform manner. ISO/TR 52018-2:2017 provides many background considerations that can help both private actors and public authorities, and all stakeholders involved, to take informed decisions. ISO/TR 52018-2:2017 does not contain any normative provision.

ISO 10077-2:2017 specifies a method and gives reference input data for the calculation of the thermal transmittance of frame profiles and of the linear thermal transmittance of their junction with glazing or opaque panels. The method can also be used to evaluate the thermal resistance of shutter profiles and the thermal characteristics of roller shutter boxes and similar components (e.g. blinds). ISO 10077-2:2017 also gives criteria for the validation of numerical methods used for the calculation. ISO 10077-2:2017 does not include effects of solar radiation, heat transfer caused by air leakage or three-dimensional heat transfer such as pinpoint metallic connections. Thermal bridge effects between the frame and the building structure are not included. NOTE Table 1 in the Introduction shows the relative position of ISO 10077-2:2017 within the set of EPB standards in the context of the modular structure as set out in ISO 52000-1.

ISO 52022-3:2017 specifies a detailed method, based on spectral data of the transmittance and reflectance of the constituent materials (solar protection devices and the glazing), to determine the total solar energy transmittance, the total light transmittance and other relevant solar-optical data of the combination. If spectral data are not available, the methodology can be adapted to use integrated data.

ISO/TR 52010-2:2017 contains information to support the correct understanding and use of ISO 52010‑1. ISO/TR 52010-2:2017 does not contain any normative provision.

ISO 15758:2014 specifies a method for calculating the density of the water vapour flow rate in cold pipe insulation systems, and the total amount of water diffused into the insulation over time. The calculation method presupposes that water vapour can only migrate into the insulation system by diffusion, with no contribution from airflow. It also assumes the use of homogeneous, isotropic insulation materials so that the water vapour partial pressure is constant at all points equidistant from the axis of the pipe. ISO 15758:2014 is applicable when the temperature of the medium in the pipe is above 0 °C. It applies to pipes inside buildings as well as in the open air.

ISO 13788:2012 gives simplified calculation methods for: The internal surface temperature of a building component or building element below which mould growth is likely, given the internal temperature and relative humidity. The method can also be used to assess the risk of other internal surface condensation problems. The assessment of the risk of interstitial condensation due to water vapour diffusion. The method used does not take account of a number of important physical phenomena including the variation of material properties with moisture content; capillary suction and liquid moisture transfer within materials; air movement from within the building into the component through gaps or within air spaces; the hygroscopic moisture capacity of materials. The time taken for water, from any source, in a layer between two high vapour resistance layers to dry out and the risk of interstitial condensation occurring elsewhere in the component during the drying process.

ISO 18292:2011 specifies a procedure for calculation of the energy performance of fenestration systems used in residential buildings, for rating of fenestration systems, doors and skylights, including the effects of frame, sash, glazing, and shading components. ISO 18292:2011 specifies procedures for the calculation of the heating and cooling energy use in residential buildings, internal and external climatic conditions, and relevant building characteristics. These procedures can accommodate all climatic conditions and installation details. It is the responsibility of the appropriate regulatory authority to identify the clauses of ISO 18292:2011 to be applied in their area of jurisdiction and the climatic data and reference building specification(s) to be used.

ISO 15927-3:2009 specifies two procedures for providing an estimate of the quantity of water likely to impact on a wall of any given orientation. It takes account of topography, local sheltering and the type of building and wall. The first method, based on coincident hourly rainfall and wind data, defines the method of calculation of the annual average index, which influences the moisture content of an absorbent surface, such as masonry, and the spell index, which influences the likelihood of rain penetration through masonry and joints in other walling systems. The second method, based on average wind data and a qualitative recording of the presence and intensity of rain (the present weather code for rain), defines a method for calculating the spell length during which an absorbent material such as masonry is moistened, having a 10 % probability of being exceeded in any year (commonly referred to as having a mean return period of 10 years). ISO 15927-3:2009 provides a comparison between the two methods. ISO 15927-3:2009 gives procedures to correct the results of both methods for topography, local sheltering and the type of building and wall. The methods included in ISO 15927-3:2009 do not apply in mountainous areas with sheer cliffs or deep gorges, in areas in which more than 25 % of the annual rainfall comes from severe convective storms, and in areas and during periods when a significant proportion of precipitation is made up of snow or hail.

ISO 15927-2:2009 gives the definition, and specifies methods of calculation and presentation of the monthly external design climate to be used in determining the design cooling load of buildings and the design of air conditioning systems.

ISO 12241:2008 gives rules for the calculation of heat-transfer-related properties of building equipment and industrial installations, predominantly under steady-state conditions. ISO 12241:2008 also gives a simplified approach for the treatment of thermal bridges.

ISO 23993:2008 gives methods to calculate design thermal conductivities from declared thermal conductivities for the calculation of the thermal performance of building equipment and industrial installations. These methods are valid for operating temperatures from -200 °C to +800 °C. The conversion factors, established for the different influences, are valid for the temperature ranges indicated in the relevant clauses or annexes.

ISO 10456:2007 specifies methods for the determination of declared and design thermal values for thermally homogeneous building materials and products, together with procedures to convert values obtained under one set of conditions to those valid for another set of conditions. These procedures are valid for design ambient temperatures between -30 °C and +60 °C. ISO 10456:2007 provides conversion coefficients for temperature and for moisture. These coefficients are valid for mean temperatures between 0 °C and 30 °C. ISO 10456:2007 also provides design data in tabular form for use in heat and moisture transfer calculations, for thermally homogeneous materials and products commonly used in building construction.

ISO 15927-6:2007 specifies the definition, method of computation and method of presentation of data on accumulated temperature differences, used for assessing the energy used for space heating in buildings. These are normally expressed in degree‑hours or degree-days, and such data are often referred to simply as "heating degree-hours" or "heating degree-days". ISO 15927-6:2007 includes approximate methods for calculating accumulated temperature differences based on hourly or daily mean temperatures and for estimating monthly values to any base temperature, for use when data computed directly from meteorological air temperature records are not available. In some countries, a threshold temperature different from the base temperature is used. ISO 15927-6:2007 does not cover this.

ISO 15927-4:2005 specifies a method for constructing a reference year of hourly values of appropriate meteorological data suitable for assessing the average annual energy for heating and cooling. Other reference years representing average conditions can be constructed for special purposes. The procedures in this part of ISO 15927-4:2005 are not suitable for constructing extreme or semi-extreme years for simulation of, for example, moisture damage or energy demand in cold years. Meteorological instrumentation and methods of observation are not covered.

ISO 15927-5:2004 specifies the definition, method of calculation and method of presentation of the climatic data to be used in determining the design heat load for space heating in buildings. These include the winter external design air temperatures and the relevant wind speed and direction, where appropriate. Heat loss through the ground, which also contributes to the heat load for buildings, depends on longer-term temperature changes; methods for calculating ground heat loss are given in ISO 13370.

ISO 15927-1:2003 specifies procedures for calculating and presenting the monthly means of those parameters of climatic data needed to assess some aspects of the thermal and moisture performance of buildings. Numerical values for any locations should be obtained from the meteorological service in the relevant country. ISO 15927-1:2003 covers the following single climate variables: air temperature; atmospheric humidity; wind speed; precipitation; solar radiation; longwave radiation. Meteorological instrumentation and methods of observation are not covered; these are specified by the World Meteorological Organisation (WMO).

ISO 15099:2003 specifies detailed calculation procedures for determining the thermal and optical transmission properties (e.g., thermal transmittance, total solar energy transmittance) of window and door systems based on the most up-to-date algorithms and methods, and the relevant solar and thermal properties of all components. Products covered by ISO 15099:2003 include windows and doors incorporating: single and multiple glazed fenestration products with or without solar reflective, low-emissivity coatings and suspended plastic films; glazing systems with pane spacing of any width containing gases or mixtures of gases; metallic or non-metallic spacers; frames of any material and design; fenestration products tilted at any angle; shading devices; projecting products.

ISO 13787:2003 establishes a procedure for the determination and verification of declared thermal conductivity, as a function of temperature, of thermal insulating materials and products used for the insulation of building equipment and industrial installations. Informative annex B gives an optional method for establishing the thermal conductivity curve or table from measured values. ISO 13787:2003 is not applicable to thermal insulating products used in building envelopes. For the procedures which are used for these products, see ISO 10456, "Building materials and products - Procedures for determining declared and design thermal values".

This International Standard defines a range of climatological data required for building design, gives guidance on methods of measurement and proposes symbols to designate them. It does not deal with suffixes or concepts combining several types of data, or values derived from basic data such as degree-days or characteristic wind speed. The definitions and symbols given in this International Standard aim to harmonize the expression of climatological data which may be drawn on when drafting regulatory and standard documents and when definitions and symbols are required for building design and construction.

ISO 13792:2011 specifies the required input data for simplified calculation methods for determining the maximum, average and minimum daily values of the operative temperature of a room in warm periods: a) to define the characteristics of a room at the design stage in order to avoid overheating in summer; b) to define whether the installation of a cooling system is necessary or not.

ISO 13791:2011 specifies the assumptions, boundary conditions, equations and validation tests for a calculation procedure, under transient hourly conditions, of the internal temperatures (air and operative) during warm periods, of a single room without any cooling/heating equipment in operation.

ISO 10077-2:2011 specifies a method and gives reference input data for the calculation of the thermal transmittance of frame profiles and of the linear thermal transmittance of their junction with glazing or opaque panels. The method can also be used to evaluate the thermal resistance of shutter profiles and the thermal characteristics of roller shutter boxes and similar components (e.g. blinds). ISO 10077-2:2011 also gives criteria for the validation of numerical methods used for the calculation. ISO 10077-2:2011 does not include effects of solar radiation, heat transfer caused by air leakage or three‑dimensional heat transfer such as pin point metallic connections. Thermal bridge effects between the frame and the building structure are not included.

ISO 13790:2008 gives calculation methods for assessment of the annual energy use for space heating and cooling of a residential or a non-residential building, or a part of it, referred to as “the building”. This method includes the calculation of: the heat transfer by transmission and ventilation of the building zone when heated or cooled to constant internal temperature; the contribution of internal and solar heat gains to the building heat balance; the annual energy needs for heating and cooling, to maintain the specified set-point temperatures in the building – latent heat not included; the annual energy use for heating and cooling of the building, using input from the relevant system standards referred to in ISO 13790:2008 and specified in Annex A. ISO 13790:2008 also gives an alternative simple hourly method, using hourly user schedules (such as temperature set-points, ventilation modes or operation schedules of movable solar shading). Procedures are given for the use of more detailed simulation methods to ensure compatibility and consistency between the application and results of the different types of method. ISO 13790:2008 provides, for instance, common rules for the boundary conditions and physical input data irrespective of the calculation approach chosen. ISO 13790:2008 has been developed for buildings that are, or are assumed to be, heated and/or cooled for the thermal comfort of people, but can be used for other types of building or other types of use (e.g. industrial, agricultural, swimming pool), as long as appropriate input data are chosen and the impact of special physical conditions on the accuracy is taken into consideration. The calculation procedures in ISO 13790:2008 are restricted to sensible heating and cooling. The energy use due to humidification is calculated in the relevant standard on the energy performance of ventilation systems, as specified in Annex A; similarly, the energy use due to dehumidification is calculated in the relevant standard on the energy performance of space cooling systems, as specified in Annex A. ISO 13790:2008 is applicable to buildings at the design stage and to existing buildings. The input data directly or indirectly called for by ISO 13790:2008 should be available from the building files or the building itself. If this is not the case, it is explicitly stated at relevant places in ISO 13790:2008 that it may be decided at national level to allow for other sources of information. In this case, the user reports which input data have been used and from which source. Normally, for the assessment of the energy performance for an energy performance certificate, a protocol is defined at national or regional level to specify the type of sources of information and the conditions when they may be applied instead of the full required input.

ISO 6946:2007 provides the method of calculation of the thermal resistance and thermal transmittance of building components and building elements, excluding doors, windows and other glazed units, curtain walling, components which involve heat transfer to the ground, and components through which air is designed to permeate. The calculation method is based on the appropriate design thermal conductivities or design thermal resistances of the materials and products for the application concerned. The method applies to components and elements consisting of thermally homogeneous layers (which can include air layers). ISO 6946:2007 also provides an approximate method that can be used for elements containing inhomogeneous layers, including the effect of metal fasteners, by means of a correction term given in Annex D. Other cases where insulation is bridged by metal are outside the scope of ISO 6946:2007.

ISO 13786:2007 specifies the characteristics related to the dynamic thermal behaviour of a complete building component and provides methods for their calculation. It also specifies the information on building materials required for the use of the building component. Since the characteristics depend on the way materials are combined to form building components, ISO 13786:2007 is not applicable to building materials or to unfinished building components. The definitions given in ISO 13786:2007 are applicable to any building component. A simplified calculation method is provided for plane components consisting of plane layers of substantially homogeneous building materials. Annex A specifies simpler methods for the estimation of the heat capacities in some limited cases. These methods are suitable for the determination of dynamic thermal properties required for the estimation of energy use. These approximations are not appropriate, however, for product characterization. Annex B gives the basic principle and examples of applications of the dynamic thermal characteristics defined in ISO 13786:2007. Annex C provides information for programming the calculation method. Annex D gives an example of calculation for a building component.

ISO 13370:2007 provides methods of calculation of heat transfer coefficients and heat flow rates for building elements in thermal contact with the ground, including slab-on-ground floors, suspended floors and basements. It applies to building elements, or parts of them, below a horizontal plane in the bounding walls of the building situated for slab-on-ground floors, suspended floors and unheated basements, at the level of the inside floor surface; for heated basements, at the level of the external ground surface. ISO 13370:2007 includes calculation of the steady-state part of the heat transfer (the annual average rate of heat flow) and the part due to annual periodic variations in temperature (the seasonal variations of the heat flow rate about the annual average). These seasonal variations are obtained on a monthly basis and, except for the application to dynamic simulation programmes in Annex D, ISO 13370:2007 does not apply to shorter periods of time.

ISO 10211:2007 sets out the specifications for a three-dimensional and a two-dimensional geometrical model of a thermal bridge for the numerical calculation of: heat flows, in order to assess the overall heat loss from a building or part of it; minimum surface temperatures, in order to assess the risk of surface condensation. These specifications include the geometrical boundaries and subdivisions of the model, the thermal boundary conditions, and the thermal values and relationships to be used. ISO 10211:2007 is based upon the following assumptions: all physical properties are independent of temperature; there are no heat sources within the building element. ISO 10211:2007 can also be used for the derivation of linear and point thermal transmittances and of surface temperature factors.

ISO 13789:2007 specifies a method and provides conventions for the calculation of the steady-state transmission and ventilation heat transfer coefficients of whole buildings and parts of buildings. It is applicable both to heat loss (internal temperature higher than external temperature) and to heat gain (internal temperature lower than external temperature). For the purpose of ISO 13789:2007, the heated or cooled space is assumed to be at uniform temperature.

ISO 14683:2007 deals with simplified methods for determining heat flows through linear thermal bridges which occur at junctions of building elements. ISO 14683:2007 specifies requirements relating to thermal bridge catalogues and manual calculation methods. Default values of linear thermal transmittance are given in Annex A for information.