The Walden Effect: Farming, simple living, permaculture, and invention.

How to get wood stove heat to a lower floor

Blocking off the attic with bubble wrap panels

Warm air being heated in a sleeve around the wood stove chimneyOur movie star neighbor's home is three stories tall, and the wood stove is in the main living space on the second floor.  He made bubble-wrap partitions (see the top photo) to close hot air out of the seldom-used third floor while letting light shine down into the living room.  But his bathroom is downstairs, so he is stuck with the difficult question --- how do you make hot air go down?

A couple of years ago, he installed a heat pump, but his experience matches my research --- heat pumps are only marginally effective in cold weather in our region.  Still, the heat pump turned out to be the solution.  Our neighbor built a sleeve around the chimney pipe of his wood stove and tapped it into the return air duct for the heat pump.  Then, when he wants to heat the downstairs, he simply turns on the fan for the heat pump.  The fan sucks hot air from above the stove, through the sleeve where it is heated even more, then down to the lower floors.  Voila --- hot air running downhill!

Ducts pull hot air from around the stove and pipe it downstairs

Looking for another ingenious invention to make your  homesteading life simpler?  Our homemade chicken waterer can save you hours of time per week.

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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I like the bubblewrap partitions; cheap and effective. Ingeneous.

But in this case I wonder about the added value of a heat pump? IMO a fan should do the trick just as well. (of course a smaller pipe filled with water would do a much better job of transferring heat, but I digress)

With regard to your conclusions about heat pumps;

heat pumps are only marginally effective in cold weather in our region.

It is too generalistic, IMO. I'm assuming you are talking about a system where air or water is fed through a relatively shallow underground loop and a heat pump is used to extract heat from it. But with things like this the devil is in the details.

A heat pump is just a device that transforms energy from a lower to a higher temperature. A specific heat pump usually has a limited temperature difference that it can generate and a limited power. Besides a heat pump, a heating system as described above installation also needs an energy collector outside and a radiator inside.

And when sizing such a system you need to have at least an idea what kind of power you'll need for heating. A thorough understanding of thermo- and fluid dynamics and the specific performance of the components used is a requirement to get a successful result.

With around 8000 MW installed world-wide(1), there can be no question that geothermal energy works.

A shallow underground heat collector is indeed by definition not very efficient because of the relatively low temperature differences involved. That does not mean that the concept of using a loop plus heat pump for heating is not worthwhile. In this case the efficiency of the loop matters little because the supplied heat is free. It just means that you'll have to use a bigger collector to get a greater heat flow! The choice of heat transfer medium will also have a big influence. E.g. water is much better at absorbing and storing heat than air. (for a quick test; hold one hand in the air and stick the other hand in a bucket of room temperature water. Which feels colder?)

Comment by Roland_Smith Mon Dec 27 15:21:31 2010

You're definitely right --- I should have been clearer and said that heat pumps as generally installed are only moderately efficient in our region. If you upgrade to producing a large-scale geothermal system, of course they would be more effective, but that costs orders of magnitude more money to install and requires a lot of flat ground, etc. When people talk about putting in a heat pump, that's generally not what they're talking about. They tend to call that a geothermal system.

Our neighbor doesn't turn on the heat pump when he's blowing hot air downstairs, just the fan. He has the heat pump for the milder part of the year, so it makes sense to use the system that's already in place to blow the hot air down even when it doesn't make sense to run the heat pump. If he didn't have the heat pump, using fans and ducts would make more sense.

Comment by anna Mon Dec 27 16:14:17 2010
A slight correction. Although geothermal is not cheap, it doesn't take a lot of space. All that is needed is room to drill a well. One could be done in your mom's back yard.
Comment by Errol Wed Dec 29 14:21:51 2010
That's a good point. I was thinking of the cheaper method of burying pipes in more of a septic field-like arrangement, rather than going straight down, but of course you're right that a well would suffice.
Comment by anna Wed Dec 29 15:05:40 2010
great idea to catch heat, in big cities codes do not allow even a screw in the pipe as this is susceptible to carbon monoxide leaking from the pipe, to create a return pressure outside this pipe will still create a negative pressure pulling and mixing carbon monoxide in with the breathable air, as licensed mechanical contractors out oath is to condemn anything reading 32ppm+ of co, i would seriously consider a really good co test (not lowes or home depots plug in carbon monoxide detectors dont pick up and sound until 80ppm+). Dr Air
Comment by Lee ONeill Sun Sep 6 11:35:50 2015

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