Summer Energy Efficiency

Summer Proofing Your Home


     We thought winter would never end, but the heat will soon have us longing for the cooler temps we just left behind. Before the heat turns up, consider these energy-efficient projects that will keep the heat at bay:

Ventilate the attic – Check to see if you have enough soffit vents and attic vents. If not, add more. These vents will release some of the hot air that can accumulate in the attic -- as much as 150 degrees Fahrenheit for dark-shingled houses. The vents can knock the temperature below 110 degrees and also prevent moisture buildup. Keep the vents clear of insulation.

Add window fans - Window fans are another means of ventilating your house. The U.S. Department of Energy says to install them in windows facing away from the prevailing wind to exhaust hot air from your home. To cool as much of your home as possible, tightly close windows near the fan and open windows in rooms far from the fan, preferably on the windward side of your home. Windows near cooler, shaded outdoor areas provide the best intake air.

Add a ceiling fan - If you use air conditioning, a ceiling fan will allow you to raise the thermostat setting about 4 degrees Fahrenheit and still be comfortable.

Upgrade your door - Install a storm door that allows you to use its screen feature on cool evenings and turn off the air conditioning.

Shade your windows – According to the Missouri Division of Energy, sunny windows make air conditioners work two to three times harder. To keep out the sun, install drapes, blinds, exterior shades and other window coverings. Applying solar control window films to existing glass is another effective method to reduce solar light and heat.

Seal your ducts - Those out-of-sight ducts can leak like sieves and account for 25 percent of your cooling costs. First seal ducts that run through the attic, crawlspace, unheated basement or garage. Use duct sealant (mastic) or metal-backed (foil) tape to seal the seams and connections of ducts. After sealing the ducts in those spaces, wrap them in insulation to keep them from getting hot in the summer or cold in the winter. Next, look to seal any other ducts that you can access in the heated or cooled part of the house. Note that if you're installing a new central air conditioner, your ducts have to be inspected anyway.

Seal out the hot air – Weather strip, caulk and insulate to keep the hot air out. The same winter insulation rules apply to summer insulation.  Here are the most important areas to insulate:

  •       Ceilings and finished attic walls
  •       Wall to unheated garage
  •       Crawl spaces
  •       All exterior walls, including basements
  •       Under floors and slabs
  •       Cathedral ceilings
  •       Dormers
  •       Around air conditioning ducts in unconditioned spaces

Have your AC ready to go – Change filters. Clean and shade your condensing unit, and remove dead leaves and grass that could block air flow. Ask your heating, ventilation and air conditioning contractor about installing dampers to restrict the flow of cooled air to rooms you rarely use and talk with the contractor about whether closing doors or registers in those rooms will affect your system’s efficiency.

Reverse fan blades - Reverse the blades on your ceiling fan so they turn counterclockwise and blow air downward.

Repaint your house lighter – If your house has a dark-colored exterior, paint it lighter to reflect more of the sun’s radiant energy. A dark color absorbs 70 to 80 percent of light rays. Same goes for shingles. Next time you have to re-roof, go lighter.

Window treatments to block summer heat

Let's say 2015 is the year you're going to improve the efficiency of your home's windows, short of actually replacing them. In summer, unprotected windows suck in heat and create the heat gain that is so uncomfortable and expensive. Here are some ideas from the U.S. Department of Energy that can reduce energy loss through windows and also can improve the appearance of your home.

Weather strip and caulk - By far the most effective thing you can do is to stop air leaks. Simple caulking and weather stripping is a do-it-yourself project for most home owners.

Awnings - Window awnings can reduce solar heat gain in the summer by up to 65 percent on south-facing windows and 77 percent on west-facing windows. That's amazing! You can use an awning to shade one window or have an awning custom made to shade the entire side of your house.

Choose an acrylic or polyvinyl laminate fabric that is water-repellent, resistant to mildew and fading, opaque and tightly woven. The lighter the awning, the more sunlight it will reflect. And make sure the awning has openings that release otherwise trapped hot air.

Blinds - Window blinds — vertical or horizontal slat-type — are more effective at reducing summer heat gain than winter heat loss. With interior blinds, you can adjust the slats to control light and ventilation. For example, when completely closed and lowered on a sunny window, highly reflective blinds can reduce heat gain by about 45 percent. Exterior roller blinds are usually made of wood, steel, aluminum or vinyl and mounted above the window. When you lower these blinds completely, their slats meet and provide shade. If partially raised, the blinds allow some air and daylight to enter through windows.

Drapes - A drape's ability to reduce heat loss and gain depends on several factors, including fabric type (closed or open weave) and color. During summer, close drapes on windows receiving direct sunlight. Studies demonstrate that medium-colored draperies with white-plastic backings can reduce heat gains by 33 percent. Drapes also stay cooler in the summer than some other window treatments because their pleats and folds lose heat through convection.

Two drapes hung together will create a tighter air space than just one. One advantage is that the room-side drape will maintain around the same temperature as the interior space, adding to a room's comfort.

High-reflectivity films - These films, which you can apply over existing windows, help block summer heat gain. They are best used in climates with long cooling seasons, because they also block the sun's heat in the winter.

Their effectiveness depends on size of window glazing area, window orientation, climate, building orientation and whether the window has interior insulation. Silver, mirror-like films typically are more effective than the colored, more transparent ones. East- and west-facing windows, because of their greater potential for heat gain, can benefit the most from these films.

Insulated panels - An insulating window panel or pop-in shutter typically consists of a core of rigid foam board insulation. You can push or clip it into the interior of a window. The panels are made so their edges seal tightly against the window frame. Seals can be made from magnetic tape or Velcro. No hardware, such as hinges or latches, is required. These panels have R-values between 3.8 and 7.

Mesh window screens - These screens can diffuse solar radiation, reducing heat gain in the summer. Screens should be mounted in an exterior frame and should cover entire windows. They are particularly effective on east- and west-facing windows.

Overhangs - Properly sized and installed roof overhangs can most effectively shade south-facing windows from the summer heat. If oriented properly, overhangs will allow the sunlight in through the windows during the winter, providing more warmth to a house. Adding overhangs to an existing house can be difficult and not always effective, so save this idea for a house under construction.

Shades - When properly installed, window shades can be one of the simplest and most effective window treatments for saving energy. Mount them as close to the glass as possible with the sides of the shade held close to the wall to establish a sealed air space. Lower shades on sunlit windows in the summer. For greater efficiency, use dual shades — highly reflective (white) on one side and heat absorbing (dark) on the other side — that can be reversed with the seasons. The reflective surface should always face the warmest side — outward during the cooling season and inward during the heating season, and they need to be drawn all day to be effective.

Shutters - Window shutters — both interior and exterior — can help reduce heat gain and loss in your home. Interior shutters need a clear space to the side of the window when they're opened.  Properly designed exterior shutters may provide the best possible window insulation system. They usually include a mechanical crank, rod or motor to allow operation from indoors.

Like window blinds, louvered shutters work best for summer shading. Movable or fixed louvers allow ventilation and natural daylight to enter a room while blocking some direct radiation. However, they won't provide much insulation against heat loss in the winter.

Storm Panels - When added to a single-pane window, a storm panel can reduce heat loss by as much as 50 percent.  Panels can be exterior or interior.  Enterior panels can be singles that you put up in the fall and take down in the spring or combination, which consists of two windowpanes and a permanent screen over the window.

Interior panels consist of flexible or rigid plastic. They are easy to install and don't have to be custom-made like exterior panels.

Shade those windows naturally

One of the best things you can do to beat heat gain in your house is to cover and shade windows. Now you can do it with manmade shutters, drapes, awnings and shades or you can do it naturally with trees and shrubs.

Shading your house with trees can reduce the solar gain that comes from dark roofs, inadequate insulation and poor attic ventilation by as much as one third, says the Iowa Energy Center. Simply by shading your house, you can reduce air conditioning costs by as much as 50 percent.

Some points to remember:

  • Plant native deciduous trees on the south and west to keep out solar heat.
  • The more shade, the more effectively you can use natural ventilation. Shade makes the air around the house cooler and prevents solar heat from being conducted indoors.
  • Temperatures directly under trees can be up to 25 degrees Fahrenheit cooler than air temperatures around asphalt.
  • Use light-colored mulch or ground cover to reflect heat away from your house.
  • Trees are a good investment. Studies by real estate agents and professional foresters estimate trees raise a home’s resale value up to 20 percent. In addition, your home’s roof and siding will last longer due to reduced exposure to ultraviolet rays.
  • Plant low bushes and shrubs to help direct summer breezes toward your house.

Ventilate now to beat the heat

Your roof can absorb a tremendous amount of heat, especially if you have dark shingles. Without proper ventilation and insulation, your attic temperature could reach 150 degrees Fahrenheit! Some of that heat is going to seep into your conditioned space and make your air conditioner work harder.

Properly ventilating your attic can help keep the attic temperature below 110 degrees. Check to see if your home’s soffit vents and attic vents are adequate, and if not, add more. The vents and louvers also will prevent moisture buildup.

Window fans are another means of ventilating your house. The U.S. Department of Energy says to install them in windows facing away from the prevailing wind to exhaust hot air from your home.  To cool as much of your home as possible, tightly close windows near the fan and open windows in rooms far from the fan, preferably on the windward side of your home. Windows near cooler, shaded outdoor areas provide the best intake air.

In multi-level houses, locate the fan on the upper level and the open windows on the lower level. If that's not practical, you may want to independently ventilate each level of your home with separate fans. Depending on the layout of your home, use several window fans working together to pull the air through your home. For instance, fans in several upstairs bedrooms will insure each bedroom is cooled and will work together to pull air in through the rest of your home.