To create a well-balanced luminance distribution the luminance of all surfaces shall be taken into consideration and will be determined by the reflectance and the illuminance on the surface. To avoid gloom and to raise adaptation levels and comfort of people in the buildings, it is highly desirable to have bright interior surfaces particularly the walls and ceilings.
The lighting designer shall consider and select the appropriate reflectance and illuminance values for the interior surfaces based on the guidance below.
- Reflectance of surfaces
Recommended reflectance’s for the major interior diffuse surfaces are:
- ceiling: 0.7 to 0.9
- walls: 0.5 to 0.8
- floor: 0.2 to 0.4
The reflectance of major object (like furniture, machinery etc) should be in the range of 0.2 to 0.7.
- Illuminance on surfaces
In all enclosed places the maintained illuminance on the major surfaces shall have the following values:
- Emavg > 50 lx with U0 >= 0.10 on the walls and
- Emavg>30lx with U0 >= 0.10 on the ceiling.
In some enclosed places such as offices, education, healthcare and general areas of entrance, corridors, stairs etc, the walls and ceiling need to be brighter. In these places it is recommended that the maintained illuminances on the major surfaces should have the following values: Em>75 lx with U0>=0.10 on the walls and Em>50lx with U0>=0.01 on the ceiling
There are standard values for interior as well as exterior lighting. Always note to know the standard lux levels for the application before doing the lighting design.