If you live in a cooling-dominated zone and are building new or replacing a roof, choose a roofing material with high reflectivity, like white and light-colored metal roofs or ceramic tiles. Most asphalt and fiberglass composite shingles, even light-colored ones, still absorb quite a bit of solar radiation. With these materials, installing radiant barriers directly underneath the roofing material or in your attic can minimize heat gain through your roof and ceiling.
Some places—for instance, South Carolina—have legislation that requires installing cool roofs on residences. The CRRC maintains a list of state codes, standards, and voluntary programs, organized by state (see Access).
No matter what climate you live in, weather-stripping and caulking leaky windows and cracks to prevent air infiltration is a good idea. Next, check insulation levels—the more insulation your home has, the better. Insulation is relatively inexpensive, durable, and works year-round. The 2012 International Energy Conservation Code (IECC) has boosted its minimum insulation requirements for all but the mildest climates (see “2012 IECC Minimum Insulation Levels” table). If you have a limited budget for improvements, most experts recommend adding insulation to a home’s attic first, since it is a major contributor to a home’s heat gain.
According to the National Renewable Energy Laboratory, shading your home can decrease indoor temperatures by at least 20°F. Shading may be accomplished naturally (shrubs, vines, and trees) or with built structures.
Trees and other plants placed around the house can provide seasonal shade and help lower the localized air temperature, since the leaves absorb heat and remove it through transpiration. But plan your planting wisely—placing vegetation against a wall stifles airflow, making your house even warmer, and also can damage siding. For cooling purposes, shrubs and small trees can work well to shade east- and west-facing windows. If your goal is also to capture passive solar gain in the winter, keep trees out of your solar window to the south. Even bare branches can create significant shade, reducing your solar gain in the wintertime. Deciduous vines, planted close to but not up against your home, may be a better choice, as their seasonal leaf loss, die-back, and much finer branches may not block passive solar gain during the winter.
Exterior shades and (to a lesser degree) interior shades can also help prevent overheating, although exterior shades are generally superior because they block sunlight before it enters a home. Another option that fits both summer passive cooling and winter passive heating goals is adjustable overhangs, such as retractable awnings. Rolling panels and shutters attached to the wall on either side of a window can also filter out some of the sun’s energy, although they’ll also restrict views. Other shading options include roll-up shades, which are best mounted on the home’s exterior to prevent heat buildup inside the building.
Creating a cooling checklist—which lists each strategy and the estimated expense of implementing it—can help you identify the most cost-effective strategies for your home. Even if you can’t retire your air conditioner for good, incorporating some of these methods can still save you energy and money—and make it easier to keep your cool.
Home Power managing editor Claire Anderson keeps her cool in her passive and active solar home in southern Oregon.
Portions of this article were adapted from “Be Cool” (HP108).
CRRC • coolroofs.org • Cool roofs
NCDC • ncdc.noaa.gov • Climate data