A few years back my family took a non-credit class on sustainable housing
through Portland Community College. There were field trips to cob, straw
bale, rammed earth, and underground homes. There was also a "stealth
solar" home/office that looked conventional from the street. The back of
the house, however, revealed the solar nature of the design. Large
south-facing windows allowed passive solar gain and warmed the concrete
floor of the first floor office. Solar panels on the roof pre-heated water
that was sent to linked natural gas hot water heaters in the garage space
on the north (street) side of the first floor. The water from these
heaters was piped through plastic tubing under the upstairs floor to heat
the living space. I seem to remember that the sun was able to do 60
percent of the water heating, even though most of the sixty-some sunny days
a year we get in Portland do not come during the heating season. The
system appeared to be much as Eric described having in his house. The
difference is that the downstairs office, which is used primarily in the
day time, does not have the tubing in the floor. It uses simply passive
solar with a concrete floor for thermal storage. There was some kind of
back up heat for the office. Might have been a small woodstove, but I
simply don't remember.
Carol (and Brodie)
-----Original Message-----
From: eric + michiko [SMTP:[EMAIL PROTECTED]]
Sent: Tuesday, April 06, 1999 10:51 PM
To: [EMAIL PROTECTED]
Subject: [ecopath] Heating Ideas
To save time, I'll edit my previously posted desciption of our system and
add what I'd do next time at the bottom.
We are heating the our down stairs (880 s.f.), and not heating the
upstairs, with hot water circulating in some fancy plastic tubing through a
thin (1.5 inch) mortar bed on a raised wood sub floor which is over a crawl
space. We are using a domestic 50 gal. natural gas hot water heater to
provide the heat, with the thought that in the future we could use a solar
(batch?) collector / heater to provide pre-heating or possibly all of the
heat some of the time. We have a circulating pump that circulates hot
water from the water heater through a heat exchanger, which transfers heat
to the water in the floor tubing. A sophisticated electronic device (by
Tekmar) senses the tubing water temperature, indoor temperature and outdoor
temperature and switches on the floor circulating pump when heat is needed
in the house and switches on the exchanger circulating pump when the water
in the floor tubing is not warm enough. It can sense changes in the need
for heat and adjust the floor tubing water temperature within one degree.
The exchanger pump rarely comes on as the loop it is on thermosyphones
enough to keep the tubing water warm. The floor circulating pump usually
runs during the night when the house had cooled off. During most days,
except the coldest and cloudiest, the sun can warm the house to at least 70
degrees. Unheated the house would cool during the night to about the low
60's, which is tolerable. With a stretch of sunny weather, it is possible
to turn the heating system down or off and live with more temperature
swing. Continuous cloudy weather, which is common in the winter here,
slowly (2 -3 days) cools the house off below a tolerable level. Our
utility bills for heating the house this winter have averaged about $23 per
month (about 42 or 43 therms of natural gas @ $0.525 / therm).
That's how it works. For someone who wants a thermostat controled,
don't-need-to-think-about system, this is a good one. Use the solar
preheat idea, make the system easy to service when necessary, use good
materials and components, think about a tankless water heater (you'll need
to make sure the circulating pump will turn on the pressure switch),
maximize the passive solar design and you'd do very well. It would be a
good improvement over current common systems.
If I did it again I wouldn't want to use such a sophisticated system.
Because I can not make or repair all parts of the system myself (or imagine
a neighbor being able to do so either) and because I think we need to learn
to minimize our use of resources and our impact on Nature, I would like to
avoid an electronic / mechanical system. I would build a house to minimize
heat loss, far beyond what is considered "adaquate" (insulated window
coverings, maximum wall and ceiling insulation (type?), few, in any,
non-south facing windows, etc.). I would rely more heavily on the passive
design to maximize direct solar gain (south windows and Trombe walls?). I
would also look into ways to heat the floor (walls, too?) through indirect
solar gain via warm water or air thermosyphoning from a collector to the
floor. Back up heat, if needed, could be provided by wood burning (masonry
stove?), possibly tied into the indirect / thermosyphone design. No
mechanical devices or electricity would be needed to do this. I'd like to
avoid parts burried in concrete, moving parts, computer chips, fossil
fuels, etc. It would, however, require daily management (opening and
closing windows and window coverings, starting a fire, etc.) of the house
for optimum heating. This kind of system, if well understood by the
occupants, could easily be adjusted, repaired, etc. and can be done under
sustainable conditions if done thoughtfully.
Well, that's about it. Anybody out there with other suggestions? What
works for you?
Eric:
