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.