Passive solar heating is a great way to provide much of your home’s heating for free. Almost every home gets some solar energy coming through the windows, but there is a vast difference between the average house and a home heated with passive solar energy.
Building a new house that is passively solar heated is not significantly more expensive than building a normal house. This makes passive solar the most cost-effective form of solar power for the new home. Every new home should be built using passive solar techniques because home heating and cooling needs can be reduced greatly – potentially to zero in certain circumstances.
All this sounds wonderful, but there is one caveat: you must find a good architect who understands passive solar design. Some architects do not understand how to do it properly and mistakes made during the building process may prove costly later.
Passive solar heating covers a wide range of strategies, including passive solar thermal hot water heaters such as the batch and thermosyphon, but it’s usually used to describe heating the house air and structure.
Direct Passive Solar Heating
The simplest form is direct passive solar heating. This involves big windows on the south side of the house. The sunlight falls onto a dark surface with a high heat storage capacity such as a masonry floor or wall painted a dark color. Water is sometimes used instead – this involves water contained in glass or transparent plastic. It has slightly different properties than solid walls, but the basic idea is the same. The wall or floor absorbs energy on sunny days, and releases it at night or on cloudy days when things get cooler.
Of course, you don’t want the house to overheat in the summer. This is generally avoided by building overhangs over the windows. In the winter the sun is at a low angle and comes in the window. In the summer, especially near midday, the sun strikes the overhang and doesn’t come into the room. This leaves the room much cooler.
Trombe Walls (Indirect Gain) and Solar Spaces (Isolated Gain)
There are two other major passive solar heating strategies, Indirect Gain and Isolated Gain. The most common Indirect Gain method is the Trombe Wall, and the most common Isolated Gain method is the solar space.
Trombe walls involve a thick wall painted a dark colour. An inch or so in front of it is glass. Sunlight enters through the glass and is absorbed as heat by the wall. The glass helps prevent heat loss, and wall slowly releases the heat into the rest of the house. Again, a Trombe wall is placed on the south side of the house.
A solar space is basically a glassed-in space on the south side of the house. They are also sometimes known as solar rooms or solaria. Solar spaces can act as greenhouses, and they are sometimes referred to as greenhouses. However, they are not the same as greenhouses designed to grow plants.
The glass is vertical, and there usually isn’t glass overhead. This is so that the glass can be shaded in the summer to avoid overheating. It also means the plants that grow there have less light than they would in a true greenhouse, although more than they would in your house. Since they are attached to the house, you may not want to grow large numbers of plants in it if you’re allergic to mildew. However, if you’ve always wanted a greenhouse,why not use it to grow plants?
These three types of passive solar heating are the most commonly used. While the systems describes here are simple and this overview is simple, there’s a lot more to passive solar design when you really start looking deeply into the subject.