[harshita]

Components of Daylight Factor
Daylight factor is the sum of all the daylight reaching on an indoor reference point from the following sources:
1.Direct sky visible from the point, expressed as the sky component (SC),
2.External surfaces reflecting light directly to the point , expressed as the externally reflected component (ERC),
3.Internal surfaces reflecting and inter-reflecting light to the point, expressed as the internally reflected component (IRC).
DF = SC+ ERC+IRC

Design variable for SC

• Area of sky  visible from  point
  
• Average altitude angle
  
• Window size
  
• Window position in relation to point
  
• Thickness of window frame member
  
• Quality of glass
  
• External obstruction 
  

Design variable for ERC

• The Area of external surface visible from the point
  
• Reflectance of external surface
  

Design variable for IRC

• Size of Room
  
• The ratio of wall etc.
  
• Surface in relation to window area
  
• Reflectance of indoor surfaces
  

To know more about illumination read .... Components of Daylight Factor
Illumination in architecture