EN ISO 13789 : Thermal performance of buildings - Transmission and ventilation heat transfer coefficients - Calculation method (ISO 13789:2017).

This standard establishes a method and conventions for calculating, under steady-state conditions, the heat transfer coefficients resulting from transmission and air exchange for whole buildings or parts of buildings. It covers heat losses when the indoor temperature is higher than the outdoor temperature, as well as heat gains in the opposite case. For its application, the temperature of the heated or cooled space is assumed to be uniform.