Sunlight availability to Windows

Sunlight is measured in terms of how many hours of sun a window will receive over the course of a year.

The BRE sunlight tests are only applicable to windows which face within 90 degrees of due south. The
BRE guidance recommends that main windows should receive at least 25% of the total annual probable
sunlight hours, including at least 5% of the annual probable sunlight hours in the winter months between
21st September and 21st March. Sunlight availability will be adversely affected if the total number of
sunlight hours falls below these targets and is less than 0.8 times the amount prior to the development.

We use computer modelling techniques which trace the path of the sun through the sky for each day of
the year. The final result is an accurate assessment of the number of sunlight hours a window will receive
both before and after the development.


Diffuse daylighting to windows
Sunlight availability to open spaces and gardens