Windows are one of the oldest passive building subsystems used in the built environment. They have been used for centuries as light sources, ventilation, heating, cooling, and communications with the outside environment. Windows have been considered. a necessary part of buildings so long that designers have neglected evaluating the benefits as a function of costs. and included them with little or no thought of cost effectiveness.

The era of subsidized low-priced energy in this country led the designers to the conclusion that the benefits of completely controlled environments were worth the energy costs to produce them. Consequently, cost effective passive subsystems, such as operable windows, high ceilings with large windows, and sun controls were replaced with convenience subsystems consuming manufactured energy. When the OPEC countries decided to place oil and gas in direct economic competition with other resources and in effect stop subsidizing energy prices, several misconceptions of energy conservation developed.