Cooling Your Home Naturally

Keeping cool indoors when it is hot outdoors is a problem. The sun beating down on our homes causes indoor temperatures to rise to uncomfortable levels. Air conditioning provides some relief. But the initial costs of installing an air conditioner and the electricity costs to run it can be high. In addition, conventional air conditioners use refrigerants made of chlorine compounds, suspected contributors to the depletion of the ozone layer and global warming.

An alternative way to maintain a cool house or reduce air-conditioning use is natural (or passive) cooling. Passive cooling uses non-mechanical methods to maintain a comfortable indoor temperature. The most effective method to cool your home is to keep the heat from building up in the first place. The primary source of heat buildup (i.e., gain) is sunlight absorbed by your house through the roof, walls, and windows. Roughly 40% of the unwanted heat that builds up in your home comes in through windows, so covering them will greatly help. Secondary sources are heat-generating appliances in the home and air leakage.

Removing Built-Up Heat

Nothing feels better on a hot day than a cool breeze. Encouraging cool air to enter your house forces warm air out, keeping your house comfortably cool. However, this strategy only works when the inside temperature is higher than the outside temperature. Natural ventilation maintains indoor temperatures close to outdoor temperatures and helps remove heat from your home. But only ventilate during the coolest parts of the day or night, and seal off your house from the hot sun and air during the hottest parts of the day.

The climate you live in determines the best ventilation strategy. In areas with cool nights and very hot days, let the night air in to cool your house. A well-insulated house will gain only 1˚F (0.6˚C) per hour if the outside temperature is 85˚ to 90˚F (29˚ to 32˚C). By the time the interior heats up, the outside air should be cooler and can be allowed indoors.

In climates with day- time breezes, open windows on the side from where the breeze is coming and on the opposite side of the house. Keep interior doors open to encourage whole- house ventilation. If your location lacks consistent breezes, create them by opening windows at the lowest and highest points in your house. This natural “thermosiphoning,” or “chimney,” effect can be taken a step further by adding a clerestory or a vented skylight. In hot, humid climates where temperature swings between day and night are small, ventilate when humidity is not excessive.

Ventilating your attic greatly reduces the amount of accumulated heat, which eventually works its way into the main part of your house. Ventilated attics are about 30˚F (16˚C) cooler than unventilated attics. Properly sized and placed louvers and roof vents help prevent moisture buildup and overheating in your attic.

Reducing Heat-Generating Sources

Often-overlooked sources of interior heat gain are lights and household appliances, such as ovens, dishwashers, and dryers. Because most of the energy that incandescent lamps use is given off as heat, use them only when necessary. Take advantage of daylight to illuminate your house. And consider switching to compact fluorescent lamps. These use about 75% less energy than incandescent lamps, and emit 90% less heat for the same amount of light.

Many household appliances generate a lot of heat. When possible, use them in the morning or late evening when you can better tolerate the extra heat. Consider cooking on an outside barbecue grill or use a microwave oven, which does not generate as much heat and uses less energy than a gas or electric range. Washers, dryers, dishwashers, and water heaters also generate large amounts of heat and humidity. To gain the most benefit, seal off your laundry room and water heater from the rest of the house. New, energy-efficient appliances generate less heat and use less energy. When it is time to purchase new appliances, make sure they are energy efficient. All refrigerators, dishwashers, and dryers display an EnergyGuide label indicating the annual estimated cost for operating the appliance or a standardized energy efficiency ratio. Compare appliances and buy the most

efficient models for your needs.

Saving Energy

Using any or all of these strategies will help keep you cool. Even if you use air conditioning, many of these strategies, particularly reflecting heat and shading, will help reduce the energy costs of running an air conditioner. However, adopting all of these strategies may not be enough. Sometimes you need to supplement natural cooling with mechanical devices. Fans and evaporative coolers can supplement your cooling strategies and cost less to install and run than air conditioners. Ceiling fans make you feel cooler. Their effect is equivalent to lowering the air temperature by about 4˚F (2˚C). Evaporative coolers use about one-fourth the energy of conventional air conditioners. Many utility companies offer rebates and other cost incentives when you purchase or install energy-saving products, such as insulation and energy-efficient lighting and appliances.