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re: hair brained solar cistern???
thu, 09 jan 2003
 wrote:

> one assumes that those swedish-code-compliant houses also use some
> form of mechanical ventilation (e.g., heat recovery ventilator),
> whereas it was pretty clear to me when i read kachadorian's book that
> he was not assuming such.

well, page 46 says:

   let there be no misunderstanding about where the fresh air makeup
   is coming from. the walls and roof of your home should be very
   tightly constructed... fresh air will enter your home through
   controlled or deliberate openings... not through gaps in the insulation
   or poorly sealed windows and doors.

a 3,000 ft^2 house with 2/3 ach has 267 cfm, enough for 18 full-time
occupants, using the 15 cfm/occupant ashrae standard.

k. doesn't mention heat recovery, although he talks about an
"air exchange or ventilator system." hrvs seem useless for
most us houses, since the natural air leaks can easily supply
most of the ventilation air. a 3,000 ft^2 house only needs
30x60/(3000x8) = 0.075 ach for 30 cfm. we might turn on
a ventilation fan if the house feels stuffy or the rh exceeds
60% in wintertime...

>> his solar slab is one good way to store overnight heat from
>> inexpensive passive air heaters or a low-thermal mass sunspace
>> that can add valuable floorspace to a house.

> in my mind, this is really the key point of the book...

we might store more heat with better room temp control by
circulating 100 f air from a sunspace under the floor...

>> one drawback is dust--it's hard to clean the rough passages in
>> the hollow concrete blocks.

> i've often wondered if it wouldn't be possible to make it easy to
> expose the ends of the rough passages (e.g, have the passages open
> into a sunspace that is a few steps down from the main level, have
> them normally covered with decorative venting of some ilk, but make
> the vent covers easy to remove). assuming such is possible, it seems
> like dealing with dust problems could be as easy as calling your local
> "monster vac" duct cleaner folks once a year. (or does the "roughness"
> of the passages make this less viable?)

that might help, but the concrete block holes are rough. some people
suggest casting 4" pvc pipes into a concrete floor...

>> a vertical thermal mass (eg a chimney with extra flues open at
>>top and bottom) might store and release heat to a house with
>>no fan power at all...

> i suspect that many people view the obsession with completely passive
> systems (i.e., no fans or pumps) as a little bit over the top, and
> would be more than willing to employ a fan or pump (and still enjoy a
> very good coefficient of performance).

if a solar house needs, say, $200 per year of electrical energy
to operate, we might heat a superinsulated house at the same cost,
and forget about fans and mass and glass...

nick






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