<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=unicode" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 9.00.8112.16450"></HEAD>
<BODY style="PADDING-LEFT: 10px; PADDING-RIGHT: 10px; PADDING-TOP: 15px"
id=MailContainerBody leftMargin=0 topMargin=0 CanvasTabStop="true"
name="Compose message area">
<DIV><FONT face=Courier>Alan Abrams <alan@abramsdesignbuild.com>
wrote:<BR><BR>> I came across a claim that a 12" thick AAC block wall
achieves R-22 (more than double the rated per unit R-value of the material
itself) in the Washington, DC climate... I am skeptical of the claim mentioned
above, and would not want to count on it for the not unusual three weeks of late
January when the daytime temp never gets out of the 20's... am I
alone?<BR><BR>No. This works best when the outdoor highs and lows are less than
and greater than 68 F...<BR><BR>On a day with average exterior temp T, a 68 F
concrete<BR>house with 2" R10 Styrofoam walls will lose or gain about |68-T|/R10
Btu/h.<BR>With min and max temps Tmin and Tmax, a frame house in the same
location<BR>with walls with an equivalent R-value might lose (68-Tmin)/R all
night and <BR>gain (Tmax-68)/R all day, with an equivalent R-value of
5(Tmax-Tmin)/|68-T|.<BR><BR>Here is a list of US locations and equivalent
R-values, based on NREL
data:<BR><BR>location
month Tmin
T Tmax equivalent
R-value<BR><BR>Philadelphia
June 61.8
71.8 81.7 26.2<BR>Phoenix,
AZ April
55.3 69.9 84.5
76.8<BR>Flagstaff
July 50.5
66.3 81.9
92.3<BR>Prescott
June 49.9
67.2 84.5
216.3<BR>Albuquerque September
55.2 68.6 81.9 222.5<BR>San
Diego
October 60.9 67.7
74.6
228.3<BR>Houston
April 58.1
68.3 78.4 338.3<BR>Ely,
NV
July 48.0
67.5 87.0 390.0<BR>Colorado Springs
August 55.2 68.3
81.3 435.0<BR>Las
Vegas
October 54.3 68.3
82.1 463.3<BR>Elkins,
WV
August 56.2 67.8
79.3 577.5<BR>Bakersfield
October 54.8 67.8
80.7 647.5<BR>Rock Springs, WY
July 52.8
68.0 83.1 infinite!</FONT></DIV>
<DIV><FONT face=Courier><BR>Nick</FONT></DIV></BODY></HTML>