|
|
re: how small is a "small house" ?
3 aug 2003
larencorie wrote:
>...i will quit cutting my firewood when i'm too old to, not because
>i want to act too old to.
then again, wood is work.
>besides, i can easily design a small super insulated passive
>solar house that can be heated with not a lot more than burning
>the junk mail, or a few sticks on the coldest winter days.
why not now? small is good, for superinsulation. a 24'x32' house with 64 ft^2
of r4 windows and rv walls and ceiling and 20 cfm of air leaks has a thermal
conductance g = 36+1600/rv. nrel data indicate it needs 24h(65-30)g btu/day
to stay 65 f on an average january day in phila.
with 0.5x32ft^2x1000 = 16k btu/day of sun entering 32 ft^2 of south windows
with 50% solar transmission and 3360 and 1680 and 760 btu entering 16, 8 and
8 ft^2 of e/w/n windows and 600 kwh/month (68.2k btu/day) of electrical usage,
24h(65-30)g = 68.2k+21.8k makes g = 107 btu/h-f, so rv = 22. you might use 6"
r24 sips with a 0.2 ach builder's guarantee.
you might burn 21.8k/10k = 2.2 pounds of junk mail or wood on a cloudy day,
eg 2200 pounds of wood (about 1/2 cord) over a 200 day heating season with
cloudy-day coin flips and overnight heat storage inside the house, or 1100
pounds with 2 days of heat storage, or 550 pounds with 3, or 275 with 4...
storing heat for d days in a row with a house temp dropping from 65 to 60 f
requires c = 2145d btu/f, eg 10725 pounds of water for 5 cloudy days in a row.
you might put 2.6" of water poly film ducts over a suspended ceiling, with
a slow ceiling fan and a thermostat, or keep 8x less water at 100 f using
warm air from a low-thermal-mass sunspace.
or just keep chopping wood. bad for the atmosphere. good for the soul.
nick
|
|
