June 2007
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Heat from the sun shining through windows and on roofs is a major reason for needing mechanical cooling systems. The most effective way to reduce solar heat is simply to block it, using shade trees, vines and trellises, metallized window films, awnings, sun screens and bright roof coatings.
Shade trees and trellised vines provide effective shading. They don’t allow the sun’s rays to reach the home and they create cool buffer zones near the home…
Effective shading can also be gained from reflective roof coatings, window films, interior window treatments, sun screens, awnings, low-e glass and reflective glass.
Reflective roofs and walls
Dark colors are inappropriate for walls and roofs in hot climates, because they absorb too much solar heat. The exterior walls and roof should be reflective to reflect unwanted solar heat.
If you repaint your exterior walls, choose white or a very light color.
When you reroof your home, choose a reflective roofing or roof coating. The most common reflective coatings are asphalt-based coatings, mixed with aluminum particles and mineral fibers. They reflect about 60 percent of solar heat hitting the roof. These reasonably-priced asphalt coatings vary in quality, mainly due to the amount of aluminum particles in each five-gallon container. The better coatings, which are more expensive, contain more aluminum and are more reflective. Be sure to stir this asphalt/aluminum coating vigorously and often during its application.
Bright white latex rubber coatings reflect up to 75 percent of solar heat. These latex coatings are more dependent on proper surface preparation than asphalt coatings. The roof surface must be clean and dry before application. Some latex coatings require a primer coat.
Most large hardware stores and lumber yards carry both asphalt and latex roof coatings. Follow the manufacturer’s instructions for surface preparation and application.
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