Daylight factor components:

The daylight reaching a particular point inside a room is made up of three principal components. The three components arrive at the same point by different types of path, as indicated in the following figure.

1. Sky component (SC):
   The light received directly from the sky.
   
2. Externally reflected component (ERC):
   The light received directly by reflection from buildings and landscape outside the room.
   
3. Internally reflected component (IRC):
   The light received from surfaces inside the room.
   

Figure-Components of daylight factor

The use of daylight factor components is a step towards predicting the daylight factors at a point. The three components can be analysed and calculated separately. The final daylight factor is the sum of the three separate components, so that:

                  DF = SC + ERC + IRC

where
DF = Daylight factor

SC= Sky component

ERC = Externally reflected component

IRC = Internally reflected component