Understanding Passive Solar Heating and Cooling

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Passive solar design has come a long way since the ’70s. Modern solar houses are attractive as well as energy efficient.
Passive solar design has come a long way since the ’70s. Modern solar houses are attractive as well as energy efficient.
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Sun spaces are a great way to take advantage of solar heat. Open the doors between the house and the sun space during the day to add heat to the house. Close the doors at night to prevent warm air from escaping.
Sun spaces are a great way to take advantage of solar heat. Open the doors between the house and the sun space during the day to add heat to the house. Close the doors at night to prevent warm air from escaping.

Being passive isn’t always a bad thing, especially when it’s passive solar heating and cooling. The idea behind passive solar is to design buildings that take advantage of natural heat from the sun in winter; and shade and wind and in the summer. Although the concept has been used in many cultures for centuries, passive solar design principles recently have been refined a great deal, even since the 1970s.

Passive solar, on it’s most basic level, works like this: Rays from the sun enter a building through windows, heat the air and are absorbed by floors, walls, furniture, etc. Some materials, such as stone, brick and plaster, more effectively absorb the heat. As the air cools at night, the absorbed heat releases into the building and maintains a comfortable temperature.

How Passive Solar Works

Kelly Lerner, architect and author of Natural Remodeling for the Not-So-Green House, says there are four things to consider when designing or remodeling a building to most effectively utilize solar energy: south-facing glass (glazing), shading, insulation and thermal mass.

“In most North American climates, the right amount of south-facing glass is 7 to 12 percent of the floor area of the building — a lot less than you might think if you’ve seen solar home designs from the ’70s,” she says. “In the ’70s, we really used too much glass with too little thermal mass, so instead of passive solar heat, we had something more like ‘passive-aggressive’ solar heat, creating buildings that were too hot during the day and too cool at night. Too much glazing can be a detriment on cold winter nights, allowing heat to escape.”

  • Published on Apr 16, 2008
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