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re: selection of heat source
8 nov 1997
greg visser wrote:
>hi y'all,
hi greg,
>...we are not opposed to heat pumps if they are truly the best choice,
>but want to consider all of the alternatives.
you might consider adding a lean-to sunspace onto the south side of the
house. mine is 32' long and 12' deep and 16' tall, made from about $500
worth of standard greenhouse components, mostly 9 $36 24' long curved
galvanized pipes and 9 $10 ground stakes for the pipes bolted to a
pressure-treated perimeter board. (commercial plastic film greenhouse
materials cost about 50 cents per square foot, and the standard labor
to put up a 30 x 100' greenhouse from scratch in a field is 3 people-1 day.
more like a tent than a house. the building inspector calls my sunspace
"hvac space," meaning more floorspace, of a sort, but no tax increase.)
my glazing is about $50 worth of uv polyethylene film in 3 large pieces.
that film is cloudy, but i'm looking forward to replacing it in a few years
with $100 worth of very clear bayer urethane film with a 10 year guarantee.
a single layer of very clear replex polycarbonate plastic is another option.
that comes in rolls 49" wide and costs about $1.25 per square foot and has
lower ir loss and a 10 year light transmittance guarantee.
my sunspace has a $200 32' x 24' woven black plastic 80%-sun-blocking
greenhouse shadecloth cover, now rolled up on top for the winter. in
the spring, i'll roll it down, using several ropes looped around the
cover and roller inside, which is 36' of 4" pvc drainpipe. i'd also like
to try replacing the thin-walled pipe with schedule 40 pipe, and adding
a couple of automobile rims to the ends, and a couple of small winches
under the eaves of the house, so i can roll the cover up and down
automatically to control the house temperature. (my house has stone walls,
with insulation outside the walls.)
the average temperature in bristol, tn in january is 34 f, with an average
daily high of 43.7, and 960 btu/ft^2/day of sun falls on a south wall. if
the sun arrives over 6 hours when the sunspace is 80 f, a square foot of r1
glazing would lose about 6(80-40)/r1 = 240 btu and gain about 0.9x960 = 860,
for a net gain on the order of 600 btu/ft^2 per day, in the form of warm air
that circulates between the sunspace and the house during the day when the
house windows are open or a fan runs. the airflow would stop at night, when
the sunspace gets cool. the house wall of my sunspace is covered with
charcoal-colored typar housewrap over fiberglass insulation, and the low-
thermal-mass floor is shredded oak ("playground mulch" at $20/yard^3) over
black poly film.
nick
nicholson l. pine system design and consulting
pine associates, ltd. (610) 489-0545
821 collegeville road fax: (610) 489-7057
collegeville, pa 19426 email: nick@ece.vill.edu
computer simulation and modeling. high performance, low cost, solar heating and
cogeneration system design. bsee, msee. senior member, ieee. registered us
patent agent. solar closet paper: http://leia.ursinus.edu/~physics/solar.html
web site: http://www.ece.vill.edu/~nick
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