Design considerations for window performance
Shading Conditions
Some shading elements, such as trees or nearby buildings, may precede the design process. Intentional shading elements, such as overhangs and shade trees, can be added to block some solar radiation. Blocking the sun's radiation before it reaches the windows is the most effective way of reducing solar heat gain. However, some shading conditions reduce the access of daylight and winter solar heat gain, so a balance is desirable that depends on climate, orientation and window type. Windows with low solar heat gain properties decrease the need for shading but also reduce the potential for winter solar heat gain.
Trees and landscaping
Deciduous trees can also provide seasonal shading. Trees and bushes are particularly useful for shading east and west facing windows from low sun angles that would not be blocked by any overhang. Besides providing shade, trees and other vegetation have also been found to reduce the summer air temperature around them by as much as 9° F due to evaporation of moisture.
Shading Comparison
The three examples below provide a comparison of annual energy costs depending on shading conditions and climate as well as on the window used.
- Shading in the Northern Zone (Heating Dominated)»
- Shading in the Central Zones (Heating and Cooling)»
- Shading in the Southern Zone (Cooling Dominated)»
Back to Design Consideration Steps»