ISO 12567-1:2010 specifies a method to measure the thermal transmittance of a door or window system. It is applicable to all effects of frames, sashes, shutters, blinds, screens, panels, door leaves and fittings.

It is not applicable to edge effects occurring outside the perimeter of the specimen, energy transfer due to solar radiation on the specimen, effects of air leakage through the specimen, and roof windows and projecting products, where the external face projects beyond the cold side roof surface.