Because of the present-day trend to simplify the exterior appearance of houses by eliminating unnecessary and costly decoration, architectural expression in houses is obtained to a large degree by the relationship of window areas to solid-wall areas. The number and placement of windows, and even the type of window, affect the architectural character of the house.

While windows must first be selected, sized and located to satisfy interior requirements, minor adjustments in size and/or location may be necessary to provide an acceptable appearance on the exterior of the house. Windows should be so used that the house gives an appearance of continuity, rather than one of unrelated glass and wall areas.