About one-fifth of all the heat that enters the average house comes through windows.... external shading is by far the most efficient method for controlling interior heat build-up. The air-wash between the shading screen and the window is also very effective. The screen should have a light-colored finish... Insulation boards placed next to the window pane at night, will help prevent heat losses through glazed openings. Overhangs and horizontal sunshades placed above south-facing windows serve effectively as heat reducers.

The Owner Built Home: A How-to-do-it Book (1972)