Glass > Light transmission and reflection

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Categories: Performance: Glass


The light transmittance and reflection of the glass should be calculated using the properties of the glass and of the surfaces including coatings

The values calculated are those at normal incidence of radiation and do not take into account the angular dependence of transmission or reflectance of materials.

The calculation includes any shading device within an IGU.


EN 410Glass in building – Determination of luminous and solar characteristics of glazing


Method of test

There is no method of test. A value is declared on the basis of calculation.


There is no classification for the radiation properties of the glass. The Product Standard requires the solar energy transmission to be declared as a value.

CE Marking

The Regulations do not give explicit limits to the light transmission. Light transmission is not explicitly regulated, however it is used in the whole building energy calculation (SBEM or similar) and is therefore an important property of the glazing. The allowable use of No Performance Determined (npd) is as follows:

Locationnpd allowed
England and WalesProbably not
ScotlandProbably not
Northern IrelandProbably not