|
|
re: how to rehab radiators (old house)
12 sep 1996
jerry fountain wrote:
>next summer we plan to replace the old arco boiler (is this company still in
>business?) to improve the efficiency. according to the oil company who had
>the old account, the consumption was between 1100 and 1400 gal of #2 for
>each of the last two winter seasons (at $1.039/gal == ouch!). this for a
>1200 sq ft brick bungalow just to the north of chicago. insulation and
>weatherstripping are our priorities before this winter.
good idea.
>any help or suggestions (books recommendations!) would be appreciated.
ok. toss that boiler and radiators. my nrel solar radiation data manual for
buildings says that an average of i=740 btu/ft^2/day of sun falls on a south
wall in chicago in december, when the average outdoor temp is t=26.6 f. in
january you get 910 btu, and the average temp is 21 f. december is the more
difficult month for solar heating, since i/(68-t)=17.9 for december and 19.4
for january.
caulking and insulating seems like a good idea, since your house now uses
about 1250 gallons of oil during your 6536 dd heating season, so its current
thermal conductivity is about 1250gx100kbtu/g/24/6536=800 btu/hr-f. atrocious.
cover the outside with 2" of dri-vit or insul-aid or polyurethane spray foam
with a mastic paint to reduce this to (1130+1250)ft^2/r10 = 220 btu/hr-f? put
even more insulation in the 1250 ft^2 ceiling? the 1995 cabo model energy code
suggests r38 for chicago ceilings, and an average r-value for walls, including
windows, of 1/(0.2188-hddx0.00001555) = 8.5 (yuck.)
how much sunspace glazing will you need to heat the house on an average day?
a square foot of single-glazed polycarbonate sunspace or "solar siding" on the
south or se or sw wall might gather 680 btu/ft^2 during 6 hours of sun on an
average december day (30% more with snow or a frozen reflecting pond in front)
and lose 6hr(80f-34f)1ft^2/r1 = 204 btu for a net gain of 476 btu/ft^2, and on
that day your newly insulated house will need 24hoursx(68-26.6)220 = 220k btu
to keep warm (less, really, since the south wall will be warmed by the sun),
so you need about 220k/476 = 460 ft^2 of low-thermal mass sunspace glazing.
(wow, that's a lot. south windows help, of course. should you count your
electrical consumption as internal heat, or use more insulation, or make the
south roof transparent, or move to sunny el paso, texas, where i/(68-t)=60?)
the brick should keep the house warm overnight, with insulation on the outside,
but for a cloudy week, you'd want 5x220k/25k = 44 drums full of water in your
solar closet. more, if you want to make hot water by warmwater convection with
with some fin tube pipe near the closet ceiling and a water heater upstairs.
gotta go,
nick
|
|
