As with all forms of solar power – solar thermal, PV panels, solar chimneys and others – the amount and quality of sunlight to which a home is exposed is extremely important in holistic home design. Thankfully, again in common with many other forms of solar power, even areas that might appear at first sight to be far too gloomy can, in fact, provide enough energy to reduce heating bills by 50% or more.
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Sunspaces – especially those attached outside the main home – are extremely popular. However, like all things, you need to carefully consider the benefits and disadvantages rather than just jumping in and building one.
Almost every passive solar building has a backup heating system, whether it's really needed or not. It is possible to design a passive solar home that heats itself, but it may not pass local building regulations. It will also be very hard to sell, as most home buyers simply won't believe that the house needs no heater other than the sun!
There are five options commonly available as backup heating for passive solar homes:
It is one of life's cruel ironies that the most common heating system in the USA is also one of the least environmentally friendly. Forced-air heating installations are present in over 60% of homes in the country. Of course, some are better than others – these systems have heat generated by solar thermal systems, heat pumps, and furnaces of all types (oil-fired, gas-fired, electric, or wood).
Regardless of what kind of backup heating system you put in your passive solar home – forced-air, radiant floor, baseboard hot-water, or something else – you're going to need a source of heat. And that means a high-efficiency boiler or furnace.
If your passive solar home is properly designed and everything is optimized, one of the most cost-effective backup heating systems available may be wall-mounted space heaters. For homes which only need an occasional top-up of heat or for infrequently-used rooms, they are ideal.
Modern wood stoves are not simple metal boxes to burn fuel in. They are much more efficient than traditional fireplaces and can be just as attractive. Stoves also rely on a renewable source of energy. Most modern wood stoves fit into one of two categories: radiant or circulating.
Masonry heaters are wood stoves with the welded steel or cast iron casing replaced by bricks and mortar. They are very efficient at warming an entire house, producing much higher temperatures from their fuel than standard metal stoves. Like all forms of heating, they have certain benefits and drawbacks.
A big part of the passive solar home equation resides in cutting down on how much heating and cooling you need. The lower your demands, the bigger the percentage you can cover with renewable solar energy. There are two main culprits of internal heat gain in the average home:
If you're designing a direct gain passive solar home, you will need to maintain a careful balance between two vital parts: the amount of glazing on each side of the house and the amount of thermal mass available inside to store and later release heat. Getting the glass-to-mass ratio wrong will result in too much or too little heating.