Passive Cooling and Fans

In practice, passive cooling means creating an environment that controls and lowers the amount of heat gain in the home without using electrical equipment such as A/C or fans. The U.S. Department of Energy (DOE) estimates that passive cooling measures can reduce energy bills by up to 40%.  Reducing your cooling or heating use saves you money because you can purchase a smaller cooling or heating system. The most effective passive cooling and or heating measures, in order of increasing cost, are:

1. Natural ventilation. By opening windows at night, you can cool the home by flushing out heat and moisture that accumulates in the home during the day;
2. Minimize indoor heat generation. For example, using energy-saving light bulbs, reducing hot water use, using smaller and more efficient appliances, and scheduling heat-producing tasks—like clothes drying—for cooler hours of the day;
3. Insulation and weatherization. Adding insulation to your home and sealing air leakages reduces convective heat transfer. It also helps prevent moisture infiltration, and makes living spaces draft-free.
4. Window shading and glazing. Solar radiation passing through windows can contribute 20% of heat gain in hot-humid climates. Window shading devices and glazing technology minimize heat gain while transmitting daylight, which reduces electrical lighting.
5. Cool roofs and attic ventilation. These are two effective ways to reduce heat gain by either reflecting heat away from the roof with special coatings or flushing heat out through the attic using vents and fans.
6. Trees and landscaping. Planting broad, leafy shade trees that block the sun will reduce the amount of solar radiation absorbed by the house. Consider that trees are water intensive to grow in dry or desert climates, and it takes many years for a tree to mature and provide adequate shade.

Cool yourself off, not your room

Fans are an important supplement to air conditioning because they remove heat by creating air movement in the room rather than mechanically pumping in cold air.  The convective air movement keeps people cool, not the room, so be sure to turn fans off when you leave the room. If you're spending time in only a few spaces in your home, using a portable fan is more efficient than firing up the central A/C system that will cool unused spaces.  You can save a substantial amount of energy by using portable or ceiling fans first, rather than relying solely on energy intensive A/Cs.  Window fans are also very effective at blowing in cool morning or evening air into a home.  Portable fans are a much smaller investment, both in purchase price and energy use over their lifetime, than air conditioning. They can greatly supplement, and in some cases, replace A/C use. When purchasing a new ceiling fan, look for ones with an ENERGY STAR® label. They typically use 20-50% less energy than standard ceiling fans.

Try using fans instead of A/C from 11 a.m. to 6 p.m. on Reduce Your Use days and you may earn a bill credit. Sign up for alerts or learn more.