The highest heat gain of buildings in the northern hemisphere is from the south and west exposures. The energy-consumption profile is reduced when windows facing these directions are shaded. Internal shading with curtains or blinds helps; external shades do too. The application of solar film on these windows is also useful. The solar film has the benefit of reducing the radiation component of the glass — thus a significant portion of the heat gain—without blocking the natural daylight that is itself an energy saver. Solar screens for critical windows help as well.
__________
Excerpt from Energy Conservation Projects.