BRE 209: SITE LAYOUT PLANNING
Diffuse Daylight to Windows
BRE Digest BR209: "Site Layout Planning for Daylight and Sunlight" provides methods for assessing the daylight availability within interiors during the planning stage of a building, through measuring the vertical sky component (VSC) - direct sky component - at the centre of each window.
It is deemed that the daylight availability will be adversely affected by a development if the VSC is less than 27% and/or less than 0.8 times the former value.
Sunlight availability to Windows
BR209 also provides a sunlight availability tests for windows within 90 degrees of due south. Windows should receive 25% of the total Annual Probably Sunlight Hours (APSH), with at least 5% being during the winter months.
Sunlight availability will be adversely affected if the total sunlight hours fall below this target and are less than 0.8 times the former value.
At Lighting Analysts we use the latest software technologies to accurately analyse the VSC and APSH receivable at the centre of windows and can quickly and efficiently optimise the proposed building envelope to ensure compliance with the BRE guidance.