Window areas are a major source of heat loss in winter and heat gain in summer.
Heat loss and heat gain can be reduced:
Through correct placement of the house on the lot in relation to the sun
Through design of the house as regards the amount of glass area and its location in the walls
Through the use of insulating glass.
Heat is lost through glass and through cracks around the sash of operating windows. This loss must be taken into consideration in determining the amount of glass to be used and the design of the heating system. Heat loss may limit the amount of glass in the house, but if insulating-windows are used instead of single-glazed ones, larger glass areas are possible.
This house is not as pleasing in appearance as the one below due to the number of unrelated glass and wall areas.
Windows in this house are sized and placed to form a pleasing relationship between glass and solid wall.
The placement of room-heating units (radiators, oil heaters, etc.) below windows eliminates cold draughts since the glass and the air around the windows are warmed.
In controlling heat gain, the location of glass areas is more important than the amount of glass. The house should be placed on the lot, and if necessary shaded so that the rays of the sun can be admitted during the winter when solar heat is desirable, but excluded during the hottest months of the summer.
Windows 
