When the summer heats up, staying cool can be a challenge. While air conditioning provides relief, these units use a significant amount of energy. Natural or passive cooling—where unwanted heat is reflected, blocked, or removed—is an environmentally friendly alternative. While new homes can be designed for passive cooling, you can use passive cooling techniques in your current home to live more sustainably and reduce your summer energy costs.

Reflecting heat

Roof. Your roof gets hot in the summer and much of that heat filters into your home. Reflective roof coatings block the sun’s ultraviolet rays, reducing surface temperatures as much as 80°F. This helps lower summer cooling costs while making your home more comfortable. Install ENERGY STAR rated cool roof products. ENERGY STAR products can reduce your cooling energy use by 10 to 15 percent.

Windows. Much of the unwanted heat that builds up in your home on hot summer days enters through the windows. Reflective window films deflect up to 97 percent of infrared heat while helping to prevent the fading of furniture, draperies, and carpeting.

Blocking heat

Landscaping. Leafy trees planted on the south and west sides of your home will provide cooling shade in summer and reduce heat gain through your roof and windows. A six- to eight-foot tree planted near your home will provide shade for windows during the first year. Depending on the species and the roof, a tree will provide roof shading within 5 to 10 years. For more information, see Landscaping from the U.S. Department of Energy.

Shading devices. Exterior shading devices—awnings, louvers, and shutters—block direct sunlight, which helps to reduce solar heat gain. Awnings installed on windows that have a southern exposure can reduce solar heat gain as much as 65 percent. Interior shading devices—draperies, blinds, or shades—are also effective at preventing solar heat gain.

Removing heat

Natural ventilation. A cool breeze feels great on a hot day. It also helps to force warm air out of your home. Open windows during the coolest part of the day or night and close them during the hot afternoon. Ventilated attics reduce accumulated heat, and are up to 30°F cooler than unventilated attics. Louvers and roof vents, when properly sized and placed, help prevent heat buildup and moisture in your attic.

Heat buildup. Heat generated from lights and appliances can add to your cooling costs and reduce comfort. Conventional incandescent light bulbs give off much of their energy as heat. Replace them with compact fluorescent lamps (CFLs) or light-emitting diodes (LEDs) which emit less heat. Avoid using heat-generating appliances, such as clothes dryers and stoves during the hottest part of the day. Also, make sure those appliances are vented properly.

While passive cooling methods can provide some cost-effective relief from the heat, most homes require supplemental cooling. Operate ceiling fans to circulate air and make rooms feel cooler. Consider installing a whole-house fan, which brings in cool air through open windows while pulling hot, humid air into the attic and outside.

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