This International Standard 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:
a) the heat transfer by transmission and ventilation of the building zone when heated or cooled to constant internal temperature;
b) the contribution of internal and solar heat gains to the building heat balance;
c) the annual energy needs for heating and cooling, to maintain the specified set-point temperatures in the building - latent heat not included;
d) the annual energy use for heating and cooling of the building, using input from the relevant system
standards referred to in this International Standard and specified in Annex A.
The building can have several zones with different set-point temperatures, and can have intermittent heating and cooling.
The calculation interval is either one month or one hour. For residential buildings, the calculation can also be performed on the basis of the heating and/or cooling season.
This International Standard 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. This International Standard provides, for instance, common rules for the boundary conditions and physical input data, irrespective of the calculation approach chosen.
Special attention has been given to the suitability of this International Standard for use within the context of national or regional building regulations. This includes the calculation of an energy performance rating of a building, on the basis of standardized conditions, for an energy performance certificate. The result can have legal implications, in particular when it is used to judge compliance with minimum energy performance levels, which can, for instance, be required to obtain a building permit. For such applications, it is important that the calculation procedures be unambiguous, repeatable and verifiable. A special situation is the calculation of the energy performance in the case of old existing buildings, if gathering the full required input would be too labour-intensive for the purpose, relative to the cost-effectiveness of gathering the input. In this case, it is important that the calculation procedures provide the right balance between accuracy and data collection costs. To accommodate the application for these and other situations, this International Standard offers different choices. It is up to national bodies whether or not to choose a specific option for mandatory use, e.g. depending on the region in the country, the type of building and its use, and on the purpose of the
assessment.
Annex H provides some information on the accuracy of the method.