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QUESTION:I was wondering if someone could help me. I'm looking for information on an
outdoor woodburner. I was a subscriber to the Mother Earth News, years ago
before it got so commercial, and they had an advertiser that offered plans
for an outdoor burner they called a Hasha, or Hasa. I've used search engines
for hours trying to find something on the subject. The idea was a
cinderblock building which housed the firebox. Sand surrounded the firebox
on all but of course the front side and you could thread copper tubing
through the sand for hot water. Ducts carried the hot air into the home and
was thermostatically controlled. Do you have any links to information to any
type of outside woodburners or to this "hasa?" We are about to close on our
ANSWER: I dismember the ad you are talking about. IIRC, the company was in Louisiana,
which puzzled me, since it isn't as cold as the northern tier states.
The idea has two primary flaws.
First, the insulation on the pipes has to be really good. If you are pushing
hot air, you have to push it to and from the furnace, X feet from the house.
This is not a good thing. If you push one-way from the furnace, the humidity
of the air will quickly drop to zero. Also, not a good thing. Hot air pipes
have a large exposed surface compared to hot water pipes.
Second, sand as a thermal sink is not as efficient as water. It may have been
used because of ease of construction, low cost, and to get around "boiler"
ordinances, but it just isn't the best material for the job.
What would make more sense is a similar structure, highly insulated, but
containing a semi open tank of water mixed with anti-oxidants. The tank cannot
be completely closed because of the danger of a boiler explosion on a home
built tank. The tank would then supply hot water only to baseboard heating in
the home.
The size of the tank is up to you, and there are redily available formulas on
how much heat it can hold.
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