re: freedom & independence
30 nov 2005
> wrote in message
>> ... "mass and glass," with a masonry floor and windows on the living
>> space... works, but there's lots of heat loss at night and on cloudy
>> days. it's better to put the windows on a low-mass sunspace or use
>> some sort of air heater, eg $1/ft^2 polycarbonate "solar siding," with
>> no airflow and no loss of heat at night.
>> where i live near phila a square foot of r2 double pane south window
>> on a living space gains about 800 btu/ft^2 per day and loses about
>> 24h(65-30)1ft^2/r2 = 420, for a net gain of 380. the same window on
>> a low mass sunspace would only lose about 6h(65-30)1ft^2/r2 = 105,
>> for a net gain of 695. the r1 solar siding would gain 900 and lose
>> 210, for a net gain of 690.
>... what is a low mass sunspace?
one without a lot of thermal mass. the (wretched) passive solar industry
council aka sustainable building industry council guidelines are heavily
influenced by brick and masonry salesmen, so they suggest putting lots of
thermal mass in a sunspace: masonry, bricks, water drums, and so on, but
that cripples the solar heating performance by storing solar heat overnight
in the sunspace and making it lukewarm all winter vs hot during the day
and cold at night, with little heat loss through the windows at night.
you can get a lot more useful house heat by not deliberately filling up
a sunspace with thermal mass. just make an insulated wall between it
and the living space and let air circulate between them during the day
and stop the air circulation at night. a passive plastic film one-way
damper ("the 7 cent solution") can do this, a dry cleaner bag, hinged
at the top, able to swing into the living space from an open window
near the top of the sunspace during the day, with some sort of screen
or mesh (chicken wire lends a nice ambiance) on the other side of the
window to keep it from swinging back into the sunspace at night. you
also need a hole near the bottom of the sunspace to allow house air
to return to the sunspace during the day for rewarming. the lower hole
doesn't need a one-way damper, if the upper one works. you could also
move air with a large window fan and sunspace and room temp thermostats
that turn on the fan when the house is cool and the sunspace is warm.
if you have no use for extra floorspace, the "sunspace" might be only a
few inches deep, eg a single layer of polycarbonate glazing over a dark
south house wall, with vent holes at the top and bottom.
>i would like to gain a better understanding about all this energy saving
>stuff because i'd like to keep my modest little house instead of being forced
>to move to one of those depressing places where so many older people live.
then again, they can mow the lawn and lift our noses out of the cornflakes :-)
>... i've read articles about saving energy but most have been about
>installing new windows, replacing old heating systems, adding insulation,
>and using landscaping to cut wind.
landscaping seems pretty useless. the first step might be airsealing, with
a blower door test. this can be free, with the pa liheap low-income program.
air leaks may account for 50% of the heating bill.
>i'm working on that end but know there are other things that can be done
>to cut my energy bills even more.
zoning is good. heat as little of the house as possible. and
"temporal zoning," eg lower thermostat settings at night.
>my goal is to cut my energy bills. maybe you can give me some ideas that be
>especially useful for my particular situation. i own an post w.w.ii house,
>built in late 40's or early 50's, wood construction, basic rectangle, about
>1,200 sq. feet on one floor, no garage but has basement , and is located
>north of pittsburgh, pa.
december is the worst-case month for solar house heating in pittsburgh...
440 btu/ft^2 of sun falls on the ground and 600 falls on a south wall on
an average 31.5 f day with a 38.6 daily max.
>the house has double-hung windows, most about 3'x5'. some have been
>replaced, but three sides of the house still need new windows, south,
>north and west sides.
they may need caulking as well. you might consider pushing foil-faced
foamboard into a lot of the windows in wintertime, with a slot at the
top for a handle and a sliver of sunlight. warm air rises, so paint
the outside foil dark behind the south windows to make them air heaters
that lose little heat at night.
>i plan to eventually replace the siding...
hey, you might use dynaglas greenhouse roofing as "solar siding" :-)
it costs about $1/ft^2 in 4'-wide corrugated sheets with a 10 year
90% light transmission guarantee and a 20-year expected lifetime. my
640 ft^2 dynaglas roof is doing fine after 8 years of golfball size
hail, 2' snows, high winds, and 130 f attic temps in december. each
square foot might gain 540 btu and lose 6h(65-35)1ft^2/r1 = 180 btu/day
in december, for a net gain of 360. an 8'x32' wall in pittsburgh might
supply 92k btu/day, like 1 therm of gas.
>and add more insulation to the attic. the place has a new 96% high-energy
>efficient gas forced air furnace and air conditioning system. (new furnace,
>ductwork, and air conditioner cut energy costs by 40-45%...
nice. more insulation sounds good.
>but gas prices have doubled so dollarwise i'm paying as much now as before
>installing a new system.)
they will probably keep rising, along with oil and heat pump equivalents...
a quote from the acknowledgements section of the psic/sbic guidelines:
although all the members of psic, especially the technical committee,
contributed to the financial and technical support of the guidelines,
several contributed far beyond the call of duty. stephen szoke, director
of national accounts, national concrete masonry association, chairman of
psic's board of directors during the development of the guildlines; and
james tann, brick institute of america, region 4, chairman of psic's
technical committee during the development of these guidelines...
gave unstintingly of their time, their expertise, and their enthusiasm.