Cooling Your Home Efficiently Although your first thought for cooling may be air-conditioning, there are many alternatives that provide cooling with less energy use. A combination of proper insulation, energy efficient windows and doors, daylighting, shading, and natural ventilation will keep homes cool in most climates. Although natural ventilation should be avoided in hot, humid climates, the other approaches can significantly reduce the need to use air-conditioning. In climates with cool, dry summer nights, nighttime ventilation can reduce or eliminate the need for air-conditioning during the day. Window fans or a whole-house fan provide effective means of exhausting the day's hot air during the night. See the Cooling Your Home With Fans And Ventilation section. However, whole-house fans can cause large heat losses during the winter, so their openings should be well insulated during the heating season. See the Installing and Using A Whole-House Fan section. In all climates, windows and shades should be kept shut during hot days to keep out the hot air and to block the warming effects of the sunshine. Evaporative coolers (also called swamp coolers) are effective in hot, arid climates. As the name implies, these coolers chill the air by evaporating water into it. Because the evaporating water provides a natural cooling effect, evaporative coolers use much less energy than standard air-conditioners. Evaporative coolers need to be covered and insulated during the heating season. See Evaporative Cooling section. If you must use air-conditioning, a central air-conditioning system will cool your house more efficiently than room conditioners. However, if you only need to cool a small portion of your house (for instance, your bedroom), a room air-conditioner may be the best choice. Choose a central air-conditioner with a high seasonal energy efficiency ratio (SEER). Room air-conditioners are labeled with their energy efficiency ratio (EER); choose a unit with a high EER. See Energy efficient Air-conditioning section. | | Passive Solar Cooling You should design buildings for cooling load avoidance. Minimization of cooling loads should be carefully addressed for both solar building and conventional energy efficient building design. Design strategies that minimize the need for mechanical cooling systems include proper window placement and daylighting design, selection of appropriate glazings for windows and skylights, proper shading of glass when heat gains are not desired, use of light-colored materials for the building envelope and roof, careful site orientation decisions, and good landscaping design. Shading Strategies: Install fixed shading devices, using correctly sized overhangs or porches, or design the building to be "self-shading." Fixed shading devices, which are designed into a building, will shade windows throughout the solar cycle. They are most effective on the south-facing windows. The depth and position of fixed shading devices must be carefully engineered to allow the sun to penetrate only during predetermined times of the year. In the winter, overhangs allow the low winter sun to enter south-facing windows. In the summer, the overhangs block the higher sun. Plant trees and/or bushes to shade the windows at the right time of day and season. Deciduous vegetation is often an attractive and inexpensive form of shading, because it follows the local seasons, not the solar calendar. In the warm south, where more shading is needed, trees leaf out earlier, while in the cold north, where solar heat is beneficial late into spring, trees wait until the weather warms up before they leaf out. Trees can be strategically planted on east and west sides to block the rising and setting sun. Bushes can be positioned to block undesirable low sun angles from the east or west. Evergreen trees trimmed so that their canopies allow low winter sun underneath but block the high summer sun can be very effective. Properly placed vegetation can also guide airflows toward buildings for natural ventilation and can block cold winter winds. Vegetation and groundcover also contribute to evaporative cooling around a building. Vegetation used for shading should be properly located so as not to interfere with solar gain to buildings in winter. Deciduous trees can reduce winter solar gain by 20% or more and should not be placed in the solar access zone. Also note that trees require maintenance, pruning, watering and feeding. As they grow they change their shading pattern, and they can be damaged or killed, leaving the building exposed. |
