Blocking the Heat

The most effective ways to block heat from entering your home are insulation, reflective barriers and shading.

Insulation: Insulating, caulking and weatherstripping are essential to keeping your home warm in cold climates, but they also help keep your home cool in hot weather. The attics of most homes absorb heat through the roof, and insulating the attic floor will keep this heat from radiating down into the house. Fiberglass insulation, at least R-30, is easy to install. The cost will be recouped quickly in lower energy bills throughout the year.
Caulking and weatherstripping doors and windows will also prevent warmer outside air from seeping into your home. The cost of these materials is very low and application is simple.

Reflective Barriers: An important consideration in passive cooling is house color. Dark-colored home exteriors absorb 70% to 90% of the radiant energy from the sun that strikes the home's surfaces. Some of this absorbed energy is transferred into your home by way of conduction, resulting in heat gain. In contrast, light-colored surfaces effectively reflect most of the heat away from your home.
Another method for reflecting incoming heat is to install a radiant barrier. This foil-faced paper can be stapled to the roof rafters on the underside of your roof. To install, start by placing a few planks over the ceiling joists, which are the 'floor' of the attic; these serve as foot-boards to stand on while stapling the foil to the rafters above. You'll have to move the foot-boards as you progress. Be careful not to step between the ceiling joists or you may fall through the ceiling; also be careful to not step near the ends of the foot boards or they'll flip up. When stapling the foil to the rafters, space the staples about 2 to 3 inches (5 to 8 cm) apart to prevent air circulation from loosening or detaching the radiant barrier.

Shading: Shading is the simplest, most effective way to cool your home and reduce energy consumption. Up to 40% of the costs of cooling can be saved by shading techniques such as landscaping, and working the drapes and blinds.

Landscaping: Trees, vines and shrubs can be used to shade your home and reduce your energy bills.

  • Trees: Just three trees, properly placed around the house, can save an average household between $100 and $250 in energy costs annually. To be most effective, trees should be strategically located on the south and west sides of your home. Deciduous trees are best, because they shade in summer and allow light and radiant heat to pass through in the winter. When choosing deciduous trees, ask your local nursery to recommend varieties which are native to your environment, fast growing and tall enough to be effective.
 
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  • Vines: Provide shading and cooling, and are quick to grow. Trellises should be placed on the hottest side of the house, and blocked out at least 6" from the wall to protect the wall and provide a buffer of cool air. Certain vines, such as deciduous clematis and wisteria, grow well in containers where open ground is unavailable. Ask your local nursery which vines are best suited to your climate and needs.

  • Shrubs: protect the lower portions of walls from heat gain by blocking sunlight. They also act as a windbreak in winter to help protect the house from cold air. Choose shrubs which are low maintenance and grow to a fixed height. Local varieties will do best.

Take care to locate trees or large bushes where their roots will be clear of underground wires, sewer lines or septic tanks , or the house foundation.

 

Drapes and Blinds: Drapes and curtains made of light-colored fabrics reflect much of the sun's rays and help reduce heat gain. The tighter the curtain is to the wall, the better it will reduce heat gain. Two-layered drapes are most effective for both summer cooling and winter heating. Blinds, although not as effective as drapes, can be adjusted to let in some light while reflecting the bulk of the sun's heat. The more reflective side of the blinds should face outward.

Shade Screens: Exterior shade screens, also called "sun screens" "shade cloths" or "solar shields", prevent sun from entering a window. These can be installed on windows exposed to direct sunlight. Shade screens are lightweight, durable and easy to install. Unlike insect screens, shade screens are specially made to block between 50 and 90 percent of the energy striking the outside of the window. The term "shading coefficient" describes the amount of heat that penetrates the screen: lower numbers mean less energy gets through. While you can see through a shade screen, the view is obscured.

   
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