Zonal cavity lighting method
This method is used for the calculation of luminance flux transfer between surfaces in an interior/space.
This method calculates average horizontal luminance as per ICS.
To obtain average luminance we need to determine the total luminance flux reaching the working plane.
Component of flux
- Direct Component - Flux which comes directly from the luminances to the working plane.
- Reflected Component - Flux which reflected from room surface and reaches the working plane.
In the zonal cavity lighting method, a fraction of the initial lamp lumen that ultimately reaches the working plane called as coefficient of utilization.
Luminaries and room surfaces becomes less clear with time and some lamps may burn out.
This effect is called light loss factor (LLF).
- Average luminance is calculated as,
E = Φ1*COU*LLF / A
Φ = Initial lamp lumens
A = Work plae area
LLF = Light loss factor
COU = Coefficient of utilization
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