You can save energy and money when you ventilate your home instead of using your air conditioner, except on the hottest days. Moving air can remove heat from your home. Moving air also creates a wind chill effect that cools your body.
Ventilation cooling is usually combined with energy conservation measures like shading provided by trees and window treatments, roof reflectivity (light-colored roof), and attic insulation. Mechanical air circulation can be used with natural ventilation to increase comfort, or with air conditioning for energy savings.
Ventilation provides other benefits besides cooling. Indoor air pollutants tend to accumulate in homes with poor ventilation, and when homes are closed up for air conditioning or heating.
Your body can cool down through three processes: convection, radiation, and perspiration. Ventilation enhances all these processes.
Convection occurs when heat is carried away from your body via moving air. If the surrounding air is cooler than your skin, the air will absorb your heat and rise. As the warmed air rises around you, cooler air moves in to take its place and absorb more of your warmth. The faster this convecting air moves, the cooler you feel.
Radiation occurs when heat radiates across the space between you and the objects in your home. If objects are warmer than you are, heat will travel toward you. Removing heat through ventilation reduces the temperature of the ceiling, walls, and furnishings. The cooler your surroundings, the less heat you’ll attract, and the more of your own excess heat you’ll lose.
Perspiration can be uncomfortable, and many people would prefer to stay cool without it. However, during hot weather and physical exercise, perspiration is the body’s powerful cool- ing mechanism.
As moisture leaves your skin pores, it carries a lot of heat with it, cooling your body. If a breeze (ventilation) passes over your skin, that moisture will evaporate more quickly, and you’ll be even cooler.
Heat accumulates in homes from several sources and can make indoor temperatures higher than outdoors even in the hottest weather. Solar energy—which enters a home primarily through the roof and windows—is a major source of unwanted heat in most climates. Appliances, lights, and occupants generate heat as well.
To use ventilation instead of air condition- ing for cooling, you should prevent heat from entering and accumulating in your home as much as possible. Some preventive measures include installing additional attic insulation, a reflective roof, awnings, and sun-blocking window treatments. Operational changes—such as reducing the use of appliances, lighting, and hot water—will also reduce accumulated heat.
When you’ve prevented as much heat accumulation as you can, develop a ventilating strategy.