Passive solar building design works year round to save on utilities. It is a cost-effective way to take a home or building 50% or more off the grid, thus making the addition oif PVs a much more affordable option for going completely off the grid. Windows, walls and floors are designed to collect, store and distribute solar energy in the form of heat in the winter and to reject solar heat in the summer. Passive solar is an economical choice because unlike PVs, it doesn't involve the use of electrical or mechanical devices.
The first animation demonstrates no solar gain at the summer solstice. A south-facing home can be sheltered from the summer sun with sheltering overhangs. This reduces heat build-up during the day, and shifts the peak cooling load to later in the evening as the sun is going down. The air-conditioning savings can be dramatic. The second animation demonstrates the full solar gain at winter solstice that can be utilized in passive solar design. During the winter, as the sun rides lower in the sky, the sun bathes walls facing southwest, south, and southeast in light -- to warm the home throughout the day.
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