It is used by Building Design engineers and architects to predict luminance and/or illuminance within buildings using standardised sun and sky condition climate data for a given geographical location.
It is a different design metric to Daylight factors which only considers the ratio of the light level inside a structure to the light level outside the structure from an overcast sky.
With CBDM, if used considerately, the facade design of a building can be optimised to maximise useful daylight whilst excluding excessive daylight, which otherwise might cause issues with glare, visual discomfort, and/or solar gains which can cause thermal comfort issues.
At the same time reducing reliance and operation of artificial lighting.
CBDM calculations are calculated within Building simulation modelling software tools for each and every hour of the year, or sometimes for smaller increments, which allows for daily and seasonal profiles to be tested and optimised [1] The key metrics reported on within CBDM software are as follows: