Design considerations for window performance

Window area

When determining the amount, size and placement of windows, factors to consider include the aesthetics of the house, the availability of views, ventilation, daylight and egress, as well as the impact of windows on solar heat gain, heat loss, and comfort.

Window area is often determined by the desire for views, light and natural ventilation. The energy impact of window heat gain and heat loss, on the other hand, may call for a more limited window area. Compared to insulated walls, windows invariably allow more heat loss and solar heat gain. However, a combination of energy-efficient windows with advantageous orientation and shading conditions can minimize the energy penalties while maximizing the benefits of winter solar gain, daylight, views, and ventilation.

Window Area Comparison

The three examples below provide a comparison of annual energy costs by window area depending on the climate and the windows used.

• Window Area in the Northern Zone(Heating Dominated)»
• Window Area in the Central Zones (Heating and Cooling)»
• Window Area in the Southern Zone (Cooling Dominated)»

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