Is Passive Solar A Viable Home Heating Option In Cold Areas?
Passive solar can be used to heat a home in colder areas, but you have to go into it with reasonable expectations. While the cold climate is a hurdle, the real issue is going to be the length of time the sun beats down upon your property. If your home receives only four or five hours of direct sunlight a day, forget it. You will never produce enough energy to keep the home warm for sufficient periods of time.
Passive solar design is very popular in warm to mild climates because it is more or less a free method for warming a home. The manipulation of the position of the home and placement of large windows in the south facing wall is typical strategies for dealing with the issue. Obviously, large windows in a cold climate are going to result in significant heat loss regardless of the quality with which they are built. So, what can you do?
There are two primary approaches to creating a passive solar design that works in the winter. One is the use of a large Trombe Wall and the other is the greenhouse approach. Let’s take a look.
Trombe Walls are popular in passive solar designs because they effectively convert sunlight to heat and are interesting from an aesthetic view point. Typically, a Trombe Wall is 8 to 12 feet in length on the south facing wall of a home. In significantly colder areas, the wall is going to need to be much larger, perhaps the full length of the home depending upon energy analysis and the cold weather expected. An energy audit of the home is the only to arrive at a definitive answer.
You are also going to have to incorporate a flip strategy for the heat. As the sun enters the glass plate and heats up the masonry of the wall, you risk losing vast amounts of it through the glass surface. This means you need to create an air circulation method whereby you draw the hot air into a secondary space behind the wall. This can simply be a closed off room or a space intended for the purpose. The circulation should be done on a timer similar to the solar thermostats used on solar hot water panels. The point is to keep the built up heat from escaping back into the environment.
The greenhouse approach simplifies matters. The essential idea is to build an insulated greenhouse to collect and store the heat of the sun during the day. Often called a sunspace, the greenhouse is similar to those used for plants. Even in cold climates, the sun will produce a magnificent amount of heat. Again, the problem is keeping the heat from escaping once it has built up. Since the sun has to come in through a transparent surface, you inevitably have the problem of the heat escaping through the same. The best option is to use a controlled timer to blow the air through to the house once certain temperatures are reached. It is not very efficient, but you have little choice.
An alternative to passive solar heating in very cold areas is biomass. Corn burning furnaces are popular. They are a much cheaper solution as are the corn kernels. This biomass energy is also much more reliable and, personally, it is the way I would go.
