This European Standard specifies a calculation method to determine the thermal transmittance of glazing with flat and parallel surfaces. This European Standard applies to uncoated glass (including glass with structured surfaces) coated glass and materials not transparent in the far infrared which is the case for soda lime glass products, borosilicate glass and glass ceramic. It applies also to multiple glazing comprising such glasses and/or materials. It does not apply to multiple glazing which include in the gas space sheets or foils that are far infrared transparent. The procedure specified in this European Standard determines the U value (thermal transmittance) in the central area of glazing. The Standard for the calculation of the overall U value of windows, doors and shutters gives normative reference to the U value calculated for the glazing components according to this standard. In addition, U values are calculated using the same procedure for other purposes, in particular for predicting: - heat loss through glazing; - conduction heat gains in summer; - condensation on glazing surfaces; - the effect of the absorbed solar radiation in determining the solar factor. The main change in this edition is that the internal and external heat transfer coefficients have been amended slightly to avoid any ambiguities. The original annex on the determination of emissivity has been removed and reference is made to EN 12898. The old annex B is now changed into annex A (normative) as the only annex of standard now.