If you are planning to build a new home, you can take tips from some of the historic homes in your region. In the South, wide porches, tall windows, and high ceilings all play a role in helping keep a home and its occupants cool(er). In the Southwest, thermal mass in the envelope (adobe brick walls) provides a buffer against the intense summer sun. In more temperate climates, a mix of these strategies married with a high-performance envelope can result in a home that needs very little, if any, mechanical cooling.
In most regions of the United States, “ranch-style” homes that orient their long axis east to west can be most successful when it comes to passive cooling and heating. This design minimizes the home’s direct gain from the summer sun while maximizing its winter solar exposure.
Once the home’s external shape has been determined, consider thermal zoning—placing living spaces based on the building’s natural susceptibility to heat gain. In extremely hot climates, cluster main living spaces along the cooler north and east sides. Place buffer zones, such as garages or porches, on your home’s west side to protect interior living spaces from gaining too much heat.&
Carefully consider window placement and window type. Identifying the dominant summer wind direction at your site can be critical in your passive cooling plans, since you can tailor your window schedule to your site’s specifics and use the prevailing breezes to your advantage. For example, casement, jalousie, and awning windows can act as air scoops, channeling breezes into a home. Windows placed on opposite sides of the house aid in cross-ventilation, routing air through the home instead of letting it stagnate.
Depending on the climate, it’s possible to do away with whole-house mechanical cooling. That’s the strategy behind Passivhaus, but you don’t necessarily have to build to these standards to be successful. The author’s home in southern Oregon, where summertime maximum temperatures regularly climb into the 90s (and even top 100°F), was purposefully designed without a central cooling system. It has a reflective metal roof; 12 inches of ceiling insulation; and high-performance windows that were placed to capture prevailing winds. Thermal mass in the concrete floor and, to a lesser degree, in earthen plaster-coated walls, act in concert to create an envelope that is more resistant to thermal fluctuations. The active systems include ceiling fans in each room and nightly heat “flushing,” which is accomplished by opening most of the windows in the house, including three clerestory windows that sit at the top of the north wall and a series of low awnings on the south wall. When the temperature outside starts to drop, windows are opened to let in the cool night breezes When temperatures start to climb in the morning, windows are shut, capturing the “coolth”—for free.
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