Isn’t it ironic that we’re contributing to global warming while cooling our homes? Heating and cooling systems in the U.S. together account for 150 million tons of carbon dioxide (CO2) pumped into the atmosphere each year, according to the U.S. Department of Energy (DOE). But there are ways to make sure your home cooling is at its most efficient:
Windows and fans. It’s the movement of air over your skin that helps you feel cool, says Harvey Sachs, director of Buildings Programs at the American Council for an Energy-Efficient Economy (ACEEE). When it first starts to warm up, don’t rush to turn on the AC. Instead, open a few windows. Fresh air is free! If windows don’t offer enough breeze, fans are much easier on electricity. A ceiling fan might use 100 watts, while an air conditioner can easily consume 30 times that. Of course, if you do air condition your house, you”ll want to make sure all doors and windows are closed and form a tight seal.
Window units. Window units are less efficient if left on in every room, but if they’re used only when needed, they can be more energy friendly than central air, which cools the whole house. To keep your window unit effective, the DOE suggests sealing gaps with foam weather stripping and locating the unit in the shadiest part of the house. Units with the federal Energy Star rating reduce electricity use by at least 10 percent over less-efficient models.
A green option. SoCool’s Mil-lennia hybrid solar air conditioner offers an 80 percent efficiency improvement over standard units, and can be powered by standard house current, solar panels or batteries. It handles a large room with drastically reduced electricity use, SoCool says. The unit is pricey, however, $2,400 to $3,000.
Swamp coolers. If you live in a hot, dry climate, an evaporative cooler (often referred to as a swamp cooler), may be the cheapest, most effective and most environmentally friendly way to cool your home. The units cool outdoor air through evaporation and blow it inside the building. Evaporative coolers cost about half as much to install as central air conditioners and use about a quarter of the energy. They do, however, require more maintenance.
Central air conditioning. As a na-tion, we’re trending toward central air. According to the U.S. Census, 89 percent of homes built in 2005 are equipped with air-conditioning systems. Central air conditioners have two basic parts, with the evaporator coil inside and the condensing unit outside. A chemical refrigerant circulates between the two heat exchangers, and through a series of processes takes heat energy from the inside air and dumps it outside, creating the cool breezes that come out of your air-conditioning ducts. Because there are two parts, you want to make sure that they match each other well and that the size of the total system matches the size of your house. “One of the greatest sins in this country is buying air conditioners like cars—by size—instead of buying them like shoes, what fits,” Sachs says, explaining that an oversized unit will cycle on and off too often, making you less comfortable and using more electricity.
It’s important to check ducts, too. If your second floor is often warmer than your first floor, leaky ducts may be the culprit. In most systems, bad ducts waste 20 to 25 percent of the energy input. Unfortunately, poorly performing ducts are not as noticeable as leaky pipes. The DOE recommends that you install duct work within the conditioned space, not the attic, wherever possible. Locate the condensing unit in the shade. Also keep the filter clear to maximize efficiency.
Unfortunately, to achieve well-matched, well-sized units with good duct work, you’re going to have to rely on a contractor, who will calculate the type of system you need based on the home size, window location, shade and other factors. Get a sense of how much is included in the quote; as with medical procedures, it’s not always best to go with the lowest bidder.
How to Speak Air Conditionese
SEER. Seasonal Energy Efficiency Ratio. This number helps estimate annual efficiency. Look for a SEER of 13 or higher. Old systems can be as low as six or seven.
R-22. Although this refrigerant is common in many air conditioning units, it is known to deplete the ozone layer. In accordance with the Montreal Protocol, it will no longer be allowed in new equipment by 2010.
R- 410a. An alternative to R-22 that does not deplete the ozone layer, R-410a is a blend of hydrofluorocarbons.
RACHAEL JACKSON is a reporter for The Wilmington, Delaware-based News Journal.