Curtain Walling: Light Transmission
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Principles
The current Product Standard does not include light transmittance. It will be a requirement of the revised Product Standard.
The determination of the light tansmittance of translucent glazings should be carried out in accordance with EN 410, or if relevent, with EN 13363-1 or 13363-2.
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. Where glazings with different radiation properties are used in the curtain wall an area-weighted average value should be given.
Standards
| EN 410 | Glass in building – Determination of luminous and solar characteristics of glazing |
| EN 13633-1 | Solar protection devices combined with glazing – Calculation of solar and light transmittance – Part 1: Simplified method |
| EN 13633-2 | Solar protection devices combined with glazing – Calculation of total solar energy transmittance and light transmittance – Part 2: Detailed calculation method |
Method of test
There is no method of test. Classification is on the basis of calculation.
Classification
There is no classification for the radiation properties of the curtain wall. The Product Standard requires the light transmission to be declared.
CE Marking
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 |