Backup Heating for Passive Solar Homes

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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:

  • Wall-mounted heaters , which burn propane or natural gas to generate heat.
  • Wood stoves and masonry heaters , which burn renewable fuels to produce warmth.
  • Forced air systems , which push warm air around the home in ducts, with heat supplied by heat pumps, furnaces (wood or otherwise), or solar thermal systems.
  • Radiant floor and baseboard systems , which take heat generated by solar thermal systems, boilers, heat pumps or furnaces and pass it to a mass storage system under the floor, or radiators in the walls.
  • Standard grid-tied systems are possible as well, but are less popular because they're non-renewable and conflict with the renewable, off-grid ideal of solar homes.

Your choice of system will be guided by your home design, your personal preference, and most of all your budget. The good news is that a passive solar home needs a much smaller backup heating setup than a traditional house, since it is only needed to top off the heat generated by the sun. There's no point installing a monster $15,000 heating system to provide $200 of top-up heating every year.

Most people have the same (or very similar) criteria for selecting the backup system. Cost is almost always at the top of the list, followed by a variety of other considerations, as shown below:

  • Cost comes first, almost every time.
  • Total heating output is usually second – matching the right output to your home's needs.
  • Comfort is usually third, including sound and smell, as well as warmth.
  • Reliability follows next. No one wants a heater that gives up in cold weather.
  • Maintenance follows immediately afterwards. If the system does break down, how easy is it to fix? And what about the ease of regular servicing?
  • In the same vein, how automatic is the system? Automation makes life easier. It also ensures a system switches on when you're away and prevents frozen pipes.
  • Response time comes after automation. Some home owners need a system that is slower to respond and delivers less heat, but runs frequently overnight during the cold season. Others need a big, quick burst of heat from time to time just to beat a particularly cold day.
  • Fuel source is, of course, an issue for most people aiming to reduce their environmental footprint and reduce dependence on non-renewable fuels.
  • Efficiency is not as important as you might think, since the system will be small and only used for top-ups. It's still important – no one likes to waste energy – but it's not one of the top priorities.
  • Finally, pollution is a consideration. It's the last item on this list but can grow in