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<DIV><STRONG><FONT size=2 face="Courier New">Corwyn <</FONT></STRONG><A
href="mailto:corwyn@midcoast.com"><STRONG><FONT size=2
face="Courier New">corwyn@midcoast.com</FONT></STRONG></A><STRONG><FONT size=2
face="Courier New">> writes:</FONT></STRONG></DIV><STRONG><FONT size=2
face="Courier New">
<DIV><BR></FONT></STRONG><STRONG><FONT size=2 face="Courier New">>Doug Kalmer
wrote:<BR>>> ... there is a considerable amount of condensation on
cold nights.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> That condensation is releasing
970 BTUs of heat per pound of water to <BR>> the outside as it
condenses...</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">The dew point of 70 F air at 50% RH
is (70+460)/(1-(70+460)ln(0.5)/9621-460</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">= 50.5 F. If a shutter with an Rs
R-value inside an R2 window leaks indoor air</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">on a 30 F night
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">and 50.53 = 30 +
IR2 = 30 + (70-30)2/(Rs+2), condensation</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">will happen if Rs is greater than
1.896. </FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2
face="Courier New">
50.5 F<BR>
Rs
| R2<BR>70 F
---www---------------www--- 30
F<BR>
-------><BR>
I</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Increasing the shutter's
R-value beyond that won't change the dew point</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">temperature at the indoor glass
surface. It can INCREASE </FONT></STRONG><STRONG><FONT size=2
face="Courier New">the heat loss</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">through the window by making
a new condensation heatflow </FONT></STRONG><STRONG><FONT size=2
face="Courier New">path with </FONT></STRONG><STRONG><FONT size=2
face="Courier New">a low</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">thermal resistance in parallel with
the R0.68 slow-moving </FONT></STRONG><STRONG><FONT size=2
face="Courier New">airfilm</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">resistance at the glass
surface, ie by making </FONT></STRONG><STRONG><FONT size=2
face="Courier New">the dry R2 window</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">into </FONT></STRONG><STRONG><FONT
size=2 face="Courier New">a moldy rotting R1.32
window.</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>