re: frugal heating this winter??
8 oct 2004
rod speed wrote:
>> serendipity wrote:
>>>...eliminate air leaks.
>> these might be 30-50% of a typical fuel bill.
>but hardly ever are in modern houses.
modern houses seem to add insulation faster than airtightness (with some
exceptions, eg sweden and canada), which lowers the overall heat loss,
but makes air leakage a larger fraction.
for instance, a 40'x60'x8' tall "modern house" in the us might have r30
walls and an r60 ceiling and 200 ft^2 of r4 windows and 0.3 ach of natural
air leakage, with 40x60/r60 = 40 btu/h-f for the ceiling + 200/4 = 50 for
windows + 1400/30 = 47 for walls + about 0.3x40x60x8/60 = 96 for 96 cfm of
air leakage, with air leaks as 100x96/(40+50+47+96) = 41% of the fuel bill.
to minimize heat loss, seal most of the leaks, then add positive ventilation,
eg a) a bathroom exhaust fan in series with a $5 humidistat or b) a reversing
fan in a central partition wall that turns all the cracks and crevices in
the house envelope into very efficient bidirectional heat exchangers.
we might use grainger's $73.25 4tm66 16" reversible fan (61 watts at 3240 cfm
on low speed), with their 2a179 $88.15 programmable cycle timer and its $4.37
5x852 octal socket. h&r (800) 848-8001 http://www.herbach.com sell a nice
$4.95 navy surplus humidistat, item number tm89hvc5203, with a 20-80% range,
a 3-6% differential, and a 7.5a 125v switch that can be wired to open or
close on humidity rise.