Glass > Light transmission and reflection
Open full view...Categories: Performance: Glass
Principles
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.
Standards
| EN 410 | Glass 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.
Classification
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:
| Location | npd allowed |
| England and Wales | Probably not |
| Scotland | Probably not |
| Northern Ireland | Probably not |