Design considerations for window performance

Orientation

Window orientation impacts how much solar radiation will enter during different times of the day and during different seasons of the year. Window orientation may significantly affect energy use, although windows with lower solar heat gain coefficients (SHGC) tend to reduce the impact of orientation on energy performance.

South-facing windows

Heat gain from the low winter sun is best achieved by concentrating windows on southerly orientations. South-facing windows are also candidates for unwanted solar heat gain during the cooling season, but they can be shaded from the high summer sun by overhangs or other top shading.

East-and west-facing windows

During the summer months, when the sun rises early and sets late, east- and west-facing windows may bear the brunt of solar heat. As the sun path moves further south during the winter, solar radiation from the east and west decreases, limiting the potential for beneficial solar heat gain.

North-facing windows

Although north-facing windows receive no direct solar radiation, diffuse radiation and possible reflections from neighboring buildings contribute some solar heat. Oftentimes, north windows allow a good view to a sunlit outdoors.

Orientation Comparison

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

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

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