How much light is admitted to the room is determined by several factors - the size of the window used, the number of windows used, the position of the windows and how the internal reveals are formed.

It is of course obvious that a bigger window admits more daylight, but it is worth considering that by strategically placing more, smaller windows a better overall effect can be achieved.

Also it can be shown that by splaying the reveals to the window considerably more light can be admitted than by the traditional 90degree return. A correctly splayed opening has the further advantage of allowing heat to pass freely over the surface of the window and thus reduce potential condensation areas.