Build a Solar Home and Let the Sunshine In

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3. Orient the longest wall of the house so it faces true south. Rectangular floor plans minimize the exposure of east and west walls to summer sun, which is especially helpful in hot climates. The front, back, or side of the house can be the south wall. (True south is not the same as the magnetic south shown by compasses. Check with a local surveyor's office to find out how many degrees to adjust from magnetic south.)

Can you deviate from a due south orientation? Sure, but you'll pay a price in dollars and thermal comfort. Straying from a solarsouth design reduces wintertime heat gain and may increase summertime solar gain, leading to overheating.

The more rooms that have some south windows, the better. This helps eliminate the need for fans or ducts to move warm air from one area to another. Place rooms that require less heat, such as workshops, bedrooms and kitchens, on the north side of the house.

4. Maximize windows on the south side. South glass should be a minimum of 7 percent of the house's square footage for a sun-tempered home and a maximum of 12 percent for fully passive-solar designs. Don't go wild on windows. North, east and west windows should follow the "Window Allocation Guidelines". Exceeding the 12 percent guideline for south windows may cause the home to overheat in summer, and may allow excess heat loss from the windows during the night and during long, cold, cloudy periods.

Coleman recommends choosing south glass carefully for your climate. Many of the new low-emissivity (low-e) coatings reduce heat loss and gain, but for south windows you do not want glass that keeps out the solar heat. She recommends south glass that has a Solar Heat Gain Coefficient (SHGC) of at least 0.5. In warmer climates with properly designed south overhangs, uncoated double-parre glass is preferred.

5. Design the roof overhangs to shade windows properly from the high summer sun. Overhangs are key to successful solar homes. Judkoff says the exact geometry of overhangs is critical for balancing the need to admit maximum sunlight in winter and minimize solar heat gain in summer. Generally, the warmer and sunnier the climate, the deeper the overhang should be. A 2-foot overhang nicely shades an 8- to 9-foot wall in most locations. Coleman recommends the Wet) site www.susdesign.com/overhang/index.html to help you design overhangs properly. If overhangs aren't possible, use insulated shutters to keep out the summer sun.

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