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What is Passive Solar?

Jacob Queen
Jacob Queen

Passive solar is an approach to keeping a house warm by taking advantage of the sun’s rays. It differs from other solar technologies because it’s basically a low-tech approach. Passive solar simply takes the warmth from the sun directly and keeps it inside the house for heating purposes, primarily using windows and good insulation. A passive solar system can keep a house warm enough to drastically reduce heating costs, and in some areas, it can completely replace other heating methods.

The most fundamental aspect of most passive solar designs is a focus on windows. Usually, designers will install a huge number of windows facing to the south to capture as much heat as they can during daylight. The windows are also usually made of special glass that takes in as much heat as possible and keeps it in the house as long as it is able.

Windows are often the key to home-based passive solar heating.
Windows are often the key to home-based passive solar heating.

Another aspect of passive solar designs is keeping the heat during nighttime hours, and this is usually done by installing a concrete wall or floor or sometimes both. Bricks and materials like adobe will also work. The heat-collecting walls or floors are typically installed in the same areas where the windows are located. These materials absorb heat and release it very slowly. That means that once night falls, the concrete will still be radiating heat constantly for a good portion of the evening, and making the house warmer in the process.

In some cases, designers may also use a special kind of wall called a trombe with a glass pane in front of it. The basic idea behind a trombe is to capture heat inside the gap between the wall and the glass. These generally work more efficiently than simply using concrete. Designers also sometimes paint their concrete walls black so they’ll be more absorptive, or they may even put water containers, which can also capture heat, inside walls made of other materials.

Sometimes houses that use passive solar design are built in a more open way so that more heat can get from the windows to other parts of the structure. They also occasionally make the window area one large room and connect it to every other room in the house if possible. In order to keep houses from getting too hot in the summer, designers may install awnings that can block the sun when desired and design the house for easier ventilation.

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    • Windows are often the key to home-based passive solar heating.
      By: Iriana Shiyan
      Windows are often the key to home-based passive solar heating.