Window Shading

Radiant or solar heat gain through windows can cause occupant discomfort and increased air conditioning costs. The more glass your building has, especially on the east, west and south exposures, the more important window shading is to improving comfort and reducing air conditioning bills.

Shading Options

There are many choices of shading materials and placement. Interior shading devices include venetian blinds, shades and draperies. These devices can block up to 65% of the existing solar radiation striking the window. Interior shading can be used to improve the aesthetics of the room as well as the comfort. Insulated drapes or shades can be used to reduce heating needs in the winter and summer heat gain. Keep in mind that interior lighting may have been designed to take advantage of daylighting. Reducing or eliminating daylighting may require some additional interior lighting.

Exterior shading can block up to 95% of the existing solar radiation. Horizontal overhangs, awnings, tinted and reflective films and louvers are commonly used for exterior shading. Tinted or reflective films placed directly on the glass do not change the exterior appearance of the building. Some films also make the glass more difficult to break, thus making this an ideal choice for security reasons as well. An awning might be preferred for reducing solar gains when building identification or aesthetic improvements are desired.

Any shading device that can be removed during winter and non-air conditioning months is desirable over a permanent device. Otherwise, heating bills may increase slightly. Interior shading has the disadvantage of not being utilized when it should be by occupants in the room, reducing the building situation and business needs.