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Ventilation for a solar heated building with a large thermosyphon air heater - Page 2

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Posted by David Delaney on October 31, 2003, 7:15 pm
On 30 Oct 2003 18:49:37 -0800,
oiledleather@yahoo.com (Michael D) wrote:


If the two streams mix significantly, it is likely
they will mix very turbulently, and that will be
the end of efficiency as the temperature of the
glazing rises and air exchange with the heat store
slows down dramatically. A high volume air
exchange with the heat store (and air heater
efficiency) requires organized separate flows of
hot and cool air.

Yes, a desirable result. Otherwise the air heater
would lose a lot of heat to the exterior. The
colder the night, the more stable the division
between the cold heavy air in the air heater and
the hot light air in the heat store. In the
absence of sun the temperature of the air heater
will quickly descend close to the temperature of
the exterior even without ventilation slots. The
slots will just speed that up.

I cannot visual it unless you are deploring leaks
in the house, which must exist, of course, but it
is the designers and builders job to build a tight
house to limit such leaks. It is also the job of
the designer to make a conservative estimate of
the leaks and include them in the heat budget.

Of course, but again we are talking about the
degree of leaking and the tightness built into the
non-air-heater part of the house. The combination
of modern tight building practice, baffles on the
ventilation slots, and the heaviness of the cold
air in the air heater, mean that there will not be
large gusts of cold air into the air heater or
house from the air heater.

Again, obviously so, but also obviously limited by
the tightness of the house. Your suggestion has
the same validity whether or not there are
ventilation slots.

I want a house that will remain livable in the
absence of purchased energy or any electricity,
purchased or not. This is *not* the same as
designing a house not to use purchased energy or
electricity. (My wife would not consent to that.)
How will the basement be heated? With fans and/or
electric resistance heat? A wood stove? Irrelevant
to my first goal. The answers will be overlays on
the solution to the first goal, and secondary in
importance in my priority set. My questions are 1)
Can a superinsulated house with an unheated
basement be comfortable otherwise without
purchased energy or electricity? I believe it can.
Would it be better if the basement were heated in
those circumstances? Of course it would. So,
relative to my goal, the questions of interest to
me are 1) Can the current proposal be improved to
heat the basement without fans or purchased heat?
If not, what are the competing proposals that heat
the basement and the rest of the house without
purchased energy or fans?

David Delaney, Ottawa

Posted by Michael D on October 31, 2003, 9:17 pm

If you send me a copy of your picture in bitmap format, I could draw a
few possible changes and send it back to you.


Posted by David Delaney on November 4, 2003, 1:15 am
 On Tue, 28 Oct 2003 17:11:59 -0500, David Delaney

I added the following text and a drawing to the
web site today.

Several advantages could be gained by replacing
the ventilation openings at the top and bottom of
the glazing by well baffled large openings low in
the east and west walls of the air heater. Warm
stale air would exit the upper half of each
opening.  Cold fresh air would enter the lower
half of each opening, forming a pool on the bottom
of the air heater. The hot absorber would pump
fresh air into the building circulation by heating
some of the air in the pool. See the following

Ventilation openings in the east and west walls
would much simpler to implement than slots in the
top and bottom of the glazing. The glazing framing
would be greatly simplified by the absence of the
ventilation slots. The wall openings would be much
more flexible than the slots, being easier to tune
for optimum performance by partly covering the
opening.  The wall openings would be easier to
screen against insects. Stale air would be
exhausted only after having been given an
opportunity to heat the glazing, slightly
increasing the efficiency of the air heater. The
openings could be well baffled against gusts of
wind by covering them with a suficient number of
layers of furnace filter. Additional baffling
could be provided by external shrouds.

David Delaney, Ottawa

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