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<DIV><STRONG><FONT size=2 face="Courier New">"Bob Waldrop"
writes</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">>>... we came up with the
present plan (which included replacing the south <BR>>> wall of our
utility room with glass to add some passive solar)<BR>> <BR>>>Have
you considered turning this 24/7 heat-losing passive solar glass into
<BR>>>an air heater with little heat loss at night >and on cloudy
days?<BR>> <BR>> I have been reading this forum for some time and your
frequent contributions <BR>> on the subject, but the math generally escapes
me</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Windows only lose heat
during times when there's a temperature difference </FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">between
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">one side
and</FONT></STRONG><STRONG><FONT size=2 face="Courier New">
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">the other, so solar air
heaters or windows on a low-mass</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">sunspace
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">that gets cold
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">at night
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">lose no
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">heat
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">at night. (If a sunspace
contains</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">lots </FONT></STRONG><STRONG><FONT
size=2 face="Courier New">of thermal mass, </FONT></STRONG><STRONG><FONT size=2
face="Courier New">it doesn't get very cold at night, so it loses lots of
heat</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">at night.)</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">NREL says 1340 Btu/ft^2 of sun
falls on a south wall on an average </FONT></STRONG><STRONG><FONT size=2
face="Courier New">35.9 F January</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">day with a 46.7 high in Oklahoma
City. A 1 ft^2 U0.25 window </FONT></STRONG><STRONG><FONT size=2
face="Courier New">with 50% solar transmission</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">on a 65 F living space would gain
0.5x1340 = 670 Btu and lose 24h(65-35.9)1ft^2xU0.25</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">= 175, for a net gain of
670-175 = 495 Btu/day. A less-expensive U0.5 window with
</FONT></STRONG><STRONG><FONT size=2
face="Courier New">80%</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">solar transmission on a low-mass
sunspace that's 80 F for 6 hours per day would
</FONT></STRONG><STRONG><FONT size=2
face="Courier New">gain</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">0.8x1340 = 1072 Btu and lose
6h(80-35.9)1ft^2xU0.5 </FONT></STRONG> <STRONG><FONT size=2
face="Courier New">= 132, for a net gain of </FONT></STRONG><STRONG><FONT size=2
face="Courier New">940 Btu/day.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">On a cloudy day, the living-space
window loses 175 Btu. The sunspace </FONT></STRONG><STRONG><FONT size=2
face="Courier New">window loses 0 Btu.</FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> it hasn't been
clear exactly what you would advocate in this situation. It
is</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> a space about
20' long, and 6' wide, with doors at either end (no east or
west</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> windows).
The windows are stock double paned patio doors, plus two double
hung</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> windows for summer
ventilation. I am always interested in anything that will
</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> help us stay warm in the
winter for less effort.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Sounds like you might a)
use the utility room as a low-mass sunspace and
circulate</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2
face="Courier New">warm </FONT></STRONG><STRONG><FONT size=2
face="Courier New">air through the house living spaces during the day and let
the utility room </FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">get cold at night, or b) turn
these utility room windows into passive solar air</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">heaters in wintertime by darkening
the south side of the R20 window insulation </FONT></STRONG><STRONG><FONT
size=2 face="Courier New">and</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">allowing solar-warmed air to flow
out of the slot during the day, automatically,</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">with no need to move the insulation
twice a day.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Patio doors and conventional
windows are OK for sunspace glazing, but they cost</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">more and
have </FONT></STRONG><STRONG><FONT size=2 face="Courier New">more wood and
less glass with lower solar transmission than some</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">other forms of glazing, eg
4'x8' 10 mil HP92W polycarbonate glazing panels with</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">2x4 frames, slightly inflated with
argon, with a tire valve. I've made about 20</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">of these
with </FONT></STRONG><STRONG><FONT size=2 face="Courier New">butyl rubber
tape seals, but I just bought one of these $400 band</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">sealing machines <A
href="http://www.simplesealers.com/fr900-horizontal-heat-sealer.html">http://www.simplesealers.com/fr900-horizontal-heat-sealer.html</A>,</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">which should make the job a lot
easier.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2
face="Courier New">Nick </FONT></STRONG> </DIV></BODY></HTML>