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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When you read about solar systems, especially solar thermal and passive systems, you may come across the "10-Degree Rule". The rule states that, wherever possible, a building should be constructed with the long axis facing within 10 degrees of true south (not magnetic south).
The reason for this rule is very simple: south-facing walls get the most sun (in the northern hemisphere). You want as much of a building as possible facing that way to gather as much heat and energy as possible.
The best advice is often the advice you hear every time you ask a question. In the case of solar energy, the best advice is always "fix everything you can fix before you start planning your project". If you plug all your leaks, improve your energy efficiency, and insulate your home properly, your solar energy installation can be smaller and will cost you less.
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).
If your home needs air filters to remove airborne pollutants, you should consider very carefully which model you buy. It needs to be big enough, efficient enough, and also good enough to remove problem particles if a home's inhabitants are asthmatic or allergic.
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.
That title might fill you with apprehension and, in many ways, you'd be right: analyzing such a complex thing as a home's energy performance without using software is a daunting task. But it is possible. There are even several books which include worksheets and detailed descriptions of how to build a more accurate assessment than the one we'll outline here.
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.
Analyzing your passive solar home's energy performance by hand is long-winded, cumbersome, and prone to error. Between ten and twenty years ago, a variety of software tools appeared on the market, ranging from DOS-based utilities to basic Windows apps.
Over time, most of these programs have disappeared. Some were discontinued because they weren't popular enough, some vanished because they were based on obsolete operating systems, and others were simply discontinued through lack of support.