ABSTRACT
The original meaning of ‘window’ was an opening in a wall or roof, but even in simple buildings a window has several components. The amount of light transmitted depends on many factors: outside, there are roof overhangs, deep reveals and shading devices; there is the glazing material itself, the dirt on it, the frame supporting it; inside, there may be blinds, curtains, window decorations and all sorts of other objects that partially block the light.
