The indoor illumination requirement for a building is 350 Lux. If the daylight factor is 2.7

Q. The indoor illumination requirement for a building is 350 Lux. If the daylight factor is 2.7 and the design sky illuminance is 9000 Lux, then the required supplementary artificial lighting is________Lux.

Ans: 107 to 107

Sol:

The three components contributing to daylight factor are: (a) sky component (SC), (b) externally reflected component (ERC), and (c) internally reflected component (IRC).
Thus, DF = SC + ERC + IRC
Daylight factor is also defined as the ratio of indoor illumination to the corresponding outdoor illumination can be taken as constant.
This constant ratio, expressed in percentage, is the daylight factor (DF), given by :

where, E_i = indoor illumination at the point of consideration & E_o = outdoor illumination from unobstructed sky.
Here, DF = 2.7, Eo = 9000 Lux.
Assume the existing indoor illumination (E_i) = ‘P’ Lux.