Diffuse daylighting to Windows

Diffuse daylight is the light received from the sun which has been diffused through the sky. Even on a
cloudy day when the sun is not visible a room will continue to be lit with light from the sky. This is diffuse
daylight.

The BRE daylight calculations measure the percentage of the sky visible from the centre of each main
window. This is known as the Sky Component. The diffuse daylighting will be adversely affected if after a
development the Sky component is both less than 27% and less than 0.8 times its former value.

The diffuse daylight test is undertaken on a window by window basis. Special techniques are used to
assess daylight to rooms which have more than window.


Sunlight availability to windows
Sunlight availability to open spaces and gardens