ISO 13790:2004 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: the heat losses of the building when heated to constant internal temperature; the annual heat required to maintain the specified set-point temperatures in the building; 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.