Are Solar Passive Homes Becoming Popular?
Timothy Peters
No, solar passive homes are not being built in massive numbers across the United States…yet. But are they becoming more popular? Yes. According to a recent Ecohome magazine report, “retrofits, solar power and water conservation [are] seen as some of the top issues this year.”
Let’s back up a minute and talk about what a solar passive home is. It’s a home that is designed to maintain heat and light, at a comfortable temperature throughout the day and night, using building and landscaping design in concert with the sun as the primary source of power. A good passive solar home design is estimated to be able to cut heating energy consumption by up to 90%.
By design, solar passive homes are well insulated and air tight. They work with natural resources to capture and apply the solar energy efficiently, and they use as few active power systems as possible to generate power. In a passive solar home, most of the windows face south. As the sunlight hits and passes through these windows, it is absorbed by high density “thermal mass” material like concrete, stone, brick, or adobe. Because these materials absorb energy rapidly and reradiate it slowly, the solar passive solar home stays at an even temperature throughout the day and night.
A good passive solar home design normally has an open floor plan so solar heat can move from the south side of the house throughout the rest of the building. Although not always necessary, small fans are sometimes used to aid air distribution, particularly if the floor plan isn’t completely open.
There are two primary types of passive solar home designs…direct gain, and indirect gain. Direct gain is considered the simplest passive solar design technique. It is the design that brings sunlight in through the south-facing windows, where it is absorbed by the thermal mass…concrete, stone, brick or adobe…typically of a dark color, and thereafter radiated into the building as the air cools. Sometimes water is used as thermal mass, because it stores twice as much heat as masonry materials per cubic foot of volume. Water thermal storage tanks, however, require carefully designed structural support and some maintenance to prevent microbial growth, and therefore are not quite as popular.
Indirect gain, otherwise referred to as Trombe walls, has thermal storage between the south-facing windows and the living space. The Trombe wall consists of an 8 to 16 inch masonry wall on the south side of the house which is painted a dark color on the outside surface. Then, either a single or double layer of glass is placed an inch or less in front of the wall’s surface, and solar heat, absorbed and stored, migrates through the wall, and later radiates into the living area.
Regardless of which design is used, passive solar buildings include the following five design elements:
* A collector – the south-facing windows through which sunlight enters
* An absorber – dark surface of the storage element that absorbs solar heat
* Thermal mass – concrete, stone, brick, adobe or water
* Distribution method – Conduction, convention or radiation method through which heat moves from the warmer material to the through material until equalized
* Control mechanism – either overhangs or awnings or other device used to regulate how much sunlight comes in.
The U. S. Energy Information Administration says that buildings are responsible for 48% of all the greenhouse gases emitted annually. Their statistics also say that 76% of all electrical power generated is for buildings.
If we are truly committed to reducing greenhouse emissions, one of the very fastest…and easiest ways to accomplish this is by adding incentives for solar energy home construction. Passive solar home construction costs are said to add an additional 10 to 15% to construction costs, and while those costs are quickly paid back with energy savings, special financing for solar passive construction would make the popularity of this building technique go up overnight.
Timothy Peters is a renewable energy enthusiast and author. He lives in Spokane, WA and enjoys teaching others how to save money on their utility bill and to help the planet through solar energy. If you want to find out more information on solar passive homes, then check out his site at: www.HomeSolarPowerExplained.com
