NBN EN 674:1998

This European Standard specifies a measurement method to determine the thermal transmittance of glazing with flat and parallel surfaces. Structured surfaces, e.g. patterned glass, can be considered to be flat. This European Standard applies to multiple glazing with outer panes which are not transparent to far infrared radiation, which is the case for soda lime glass products, borosilicate glass and glass ceramics. Internal elements may be far infrared transparent.