Most of us who live where summers are hot have been through it: As temperatures rise into the triple digits, we crank the AC—then feel the anxiety as we open our electric bills. Americans want to feel comfortable indoors when outdoor temperatures climb—so much so that we collectively spend more than $15 billion each year on air conditioning (the equivalent of about 140 million tons of CO2 emissions). But the irony is that, while draining our wallets to keep our houses cool, we’re burning enough fossil fuels to help make the world a warmer place. Fortunately, by taking advantage of advances in energy-efficient technology and borrowing some natural cooling wisdom from the days before air conditioning was widely available, you can learn how to keep your house cool without racking up huge energy bills or carbon footprints.
Lessen the Load
The less heat that builds up inside our homes, the less we have to rely on our AC units. Begin with a few simple no- to low-budget changes:
• Close windows and window coverings in the morning before the day heats up, then open them in the evening to flush your house with cooler air.
• Turn off lights when not in use—especially incandescents, which give off a lot of heat. Replace incandescent bulbs with cooler light-emitting diodes (LEDs) or compact fluorescents (CFLs).
• Unplug electronic equipment when not in use, or use a “smart” power strip to completely power off electronics; most electronics use electricity—and generate heat—even when they are turned off.
• Do your laundry, ironing and cooking during the cooler parts of day—or use a clothesline, cook outdoors and opt for meals that don’t require cooking. Precooking large quantities of grains or vegetables in the evening can reduce daytime cooking needs and save time throughout the week.
Next, make it harder for outdoor heat to get into your home. The following changes cost some money, but your local government or utility company may offer rebates, discounts or attractive financing programs for energy-efficiency upgrades. If your summers are only moderately hot, these measures may be all you need to stay comfortable indoors. And even if you still need mechanical cooling, these steps will keep more cool air inside and more hot air outside, reducing air-conditioning needs.
• Beef up the insulation in your attic—your home will become much more comfortable and your utility bills will shrink in both summer and winter. If you already have attic insulation, check how much is there. Many homes have R-11 or R-15 attic insulation; increasing to R-30 or R-40 will make a big difference in comfort and cost. (The higher the R-value, the greater the insulation level.)
• Weatherstrip, seal and caulk leaky doors and windows; seal air leaks between your living space and the attic; and install foam gaskets behind outlet covers to keep hot air from entering and cooled air from leaving your house. Read a DIY guide to weatherproofing your home in “Sealing Air Leaks for Increased Home Efficiency.”
• Seal and insulate your ducts. Prevent cold air from leaking into your attic or crawl space en route to the conditioned areas of your home by sealing the seams between sections of ductwork with mastic sealant and wrapping ducts in insulation.
• Replace an old refrigerator with an energy-efficient model; they give off much less heat, and your local utility may offer rebates on new refrigerators.
• Heat enters homes through our windows, especially if they’re not high-efficiency. You can reduce heat gain by applying a solar-control window film or installing solar screens. You can also improve the overall efficiency of single-pane windows by installing storm windows or by replacing windows with well-insulated, heat-reflecting models.
• If you’re planning to re-roof or paint your home’s exterior, use light colors to reflect the sun’s heat. Consider metal roofs, which help reflect the sun and keep houses cool.
Learn how to keep your house cool naturally by taking advantage of Mother Nature’s tricks—especially shade and breezes. When outdoor air is cooler than indoor air, just opening windows and doors to let air flow through our houses can have a natural cooling effect. For maximum ventilation, open windows high and low in the house, which creates a stack effect, pulling cool air into the house down low and releasing hot air up high. Or open windows at both ends of a house to let air move freely through the whole structure.
Smart shading can also help reduce indoor temperatures. A landscape designed to properly shade a home can reduce air-conditioning bills by 15 to 50 percent. You can shade your home with landscaping including shrubbery, shade trees (this takes time, but it’s worth it) and vine-covered trellises, as well as with awnings and porch roofs. Place shade-casting items where they’ll block the most sun from windows and walls during the hottest parts of the day. Get a guide to landscaping for improved energy efficiency in “Plant Your Way to Energy Savings: Landscaping for Energy Efficiency.”
What if natural breezes aren’t enough? Make your own breeze with fans. Yes, they draw electricity, but fans use much less power than air conditioners, and they may be all you need to help stay cool.
Keep this in mind: Fans cool people, not spaces. Air motion over our skin helps evaporate sweat and transport our body heat away from us, which can help us feel three to four degrees cooler. So make sure to set up fans so occupants are in the path of the moving air, and don’t leave a fan on in an unoccupied room.
You can use many types of fans to keep yourself cool. Ceiling fans, long a staple of Southern summer comfort, are designed to produce a draft throughout the entire room. Table and floor fans are portable, so you can set them up wherever you’ll be. Window fans help move air between indoors and outdoors. As there’s little benefit in pulling hot outdoor air into your house, their best use is for sucking hot air out of the house when outdoor air is cool.
Even better for that job is a whole-house fan; installed in the attic, it draws cool air into the home through windows, forcing hot air out through attic vents. A whole-house fan should be operated in the early morning or after sundown.
Be Smart, Be Cool
In many climates, lessening the load, cooling naturally and using fans could be all you need for summer comfort. But if you have really hot, humid summers, you’ll probably want a boost from an air conditioner. To help you save money on the AC you use, first try setting your thermostat higher when you’ll be out of the house; there’s no point in keeping all that air cool when nobody’s there to enjoy it.
And even when you’re home, try setting the thermostat for a slightly warmer temperature—it pays. According to the American Council for an Energy-Efficient Economy, for each degree you raise your thermostat, you’ll save 3 to 5 percent in cooling costs. That means by setting the temperature five degrees higher, you could save 15 to 25 percent on your energy bills.
Finally, for efficient AC operation, keep up with maintenance:
• Check and clean or replace filters monthly; dirty filters restrict airflow and can cause the system to run longer, increasing energy use.
• Make sure indoor supply and return grilles aren’t blocked by furniture or other objects.
• Every two to three years, hire a professional to inspect, clean and tune your system; this could save as much as 15 percent on your AC costs.
Carol Venolia is a pioneering eco-architect, founder of Come Home to Nature, and coauthor of Natural Remodeling for the Not-So-Green House.
Time to replace?
If your AC unit is more than 12 years old, it’s time to consider replacing it. New energy-efficient air conditioners use up to 40 percent less energy than older models. Here are some shopping pointers:
• Look for the Energy Star label, which indicates the most efficient products.
• Check for a high SEER (seasonal energy efficiency ratio) for central ACs and a high EER (energy efficiency ratio) for room units.
• Hire a pro to properly size your AC; oversized equipment wastes money and energy.
• For hot, dry summers, evaporative coolers (also called swamp coolers)—which cool air using water evaporation—are a simple, relatively inexpensive solution.
• If you also need a new heating system, consider installing a heat pump, which can be more efficient than a standard AC.
• A ductless mini-split system may be appropriate for a room addition, or if you don’t have a ducted central heating system to piggy-back onto; in these systems, each room has its own unit, which allows you to fine-tune the temperature room by room.
American Council for an Energy-Efficient Economy
California Energy Commission Consumer Energy Center
Flex Your Power
U.S. Department of Energy
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