CEN/TC 89/WG 4 - Energy use of buildings

Energy labelling of buildings requires a method valid for both new and existing buildings, and treating them in an equivalent way.
In new buildings all required information exists to compute energy use, when necessary using conventional occupancy data; but the actual energy use is not available. In existing buildings, actual energy use is known in some cases from energy meters, but often some information, such as U-values of components or actual air change rate is missing. Since energy use for space heating and cooling strongly depends on occupants' behaviour and that different uses are involved, actual energy use cannot be used for energy labelling of the building without correction.
Therefore, a methodology should be developed to get the same results from different sets of data. The work will propose a methodology to assess missing data and to calculate a "standard" energy use for space heating and cooling. This work item also includes a methodology that allows determining the energy effectiveness of possible improvements.

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.

This European Standard specifies:
a)   overall indicators to express the energy performance of whole buildings, including heating, ventilation, air conditioning, domestic hot water and lighting systems. This includes different possible indicators;
b)   ways to express energy requirements for the design of new buildings or renovation of existing buildings;
c)   procedures to define reference values;
d)   ways to design a procedure for building energy certification.
The standard can be applied to a group of buildings, if they are on the same lot, if they are serviced by the same technical building systems and if no more than one of them has a conditioned area of more than
1 000 m2.
This European Standard provides different options at different levels. When this European Standard is used to set up national or regional methods for expressing energy performance and/or for energy certification of buildings, the choices between the options is not made by the individual user, but by authorized national or regional bodies.

This standard gives a simplified calculation method for assessment of the annual energy use for space heating of a residential or a non-residential building, or a part of it, which will be referred to as "the building".
It does not apply to buildings with air conditioning systems likely to provide space cooling during the heating season.
This method includes the calculation of:
1. the heat losses of the building when heated to constant internal temperature;
2. the annual heat required to maintain the specified set-point temperatures in the building;
3. the annual energy required by the heating system of the building for space heating, using heating system characteristics which are to be found in specific European or International standards, or, by default, in national documents.
The building can have several zones with different set-point temperatures, and can have intermittent heating.
The calculation period is the month. For residential buildings the calculation can also be performed for the heating season. Monthly calculation gives correct results on an annual basis, but the results for individual months close to the beginning and the end of the heating season can have large relative errors. Annex J provides some information on the accuracy of the method.

This standard gives a simplified calculation method for assessment of the heat use and energy needed for space heating of a residential building, or a part of it, which will be referred to as "the building". This method includes the calculation of: 1) the heat losses of the building when heated to constant temperature; 2) the annual heat needed to maintain the specified set-point temperatures in the building; 3) the annual energy required by the heating system of the building for space heating. The building may have several zones with different set-point temperatures.

This standard specifies a method and provides conventions for the calculation of the transmission heat loss coefficient of buildings and parts of buildings. For the purpose of this standard, the heated space is assumed to be at uniform temperature. Heat loss by ventilation is not within the scope of this standard. However, in order to evaluate transmission heat loss through unheated spaces, this standard gives conventional values of air change rates of such spaces. Annex A provides a steady state method to calculate the temperature in unheated  spaces adjacent to heated buildings.

This Standard definies the characteristics related to dynamic thermal behaviour of complete building components and gives method for their calculation. It also specifies the information on building materials required for its use. Since the characteristics depend on the way materials are combined to form building elements, the standard is not applicable to building materials, or to unfinished building components.