Daylight factors and ADF%











The average levels of daylighting within rooms can be assessed in LUA. ADFs are expressed a % ratio of average illuminance falling on the workplane divided by the unobstructed external illuminance.

Best practice minimum % levels have been set within BS 8206-2: Code of Practice for general daylighting are:

– 5% for a well daylit space
– 2% for a partial daylit space

If the % falls below 2% it is likely that artificial lighting will be required.

BS 8206-2 also defines the % minimum levels for housing:

– 2% for kitchens
– 1.5% for living rooms
– 1% for bedrooms

Levels of over 6% may be an indicator for overheating/heat loss problems.


ADF’s are currently being validated against CIE 171