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<DIV>Depending on where the home you're modeling is located, thermal mass in exterior walls may or may not have a significant impact on the energy use of the home. Generally speaking, thermal mass in exterior walls has the greatest impact on energy use in climates with large diurnal temperature swings that cross the interior balance point of the home. This tends to occur most often in high desert climates.</DIV>
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<DIV>Because REM/Rate does not employ hourly simulation, it cannot explicitly model the dynamic effects of mass in exterior walls. However, there is an attempt to account for the impact of mass in exterior walls in REM/Rate using climate-specific U-value adjustment factors from 2003 and previous versions of the IECC.</DIV>
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<DIV>Dave</DIV>
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<DIV>David R. Roberts, P.E.<BR>Senior Engineer<BR>Architectural Energy Corporation<BR><BR>>>> "Christian Stalberg" <cstalberg@southern-energy.com> 1/17/2008 12:57 PM >>><BR><IMG class=shape style="DISPLAY: none; WIDTH: 0px; HEIGHT: 0px" height=0 src="cid:QESTKLGJTOHZ.IMAGE_7.gif" width=0 v:shapes="_x0000_Mail" v:src="cid:image001.gif@01C85918.D7A39BD0"> </DIV>
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<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN style="FONT-SIZE: 10pt; COLOR: navy">I’m doing a modeling comparison in REM/Rate of two identical houses except one has 8” insulated core masonry block walls whereas the second has 4” wood stud insulated walls. Both walls end up having comparable U values. REM/Rate shows negligible difference in energy usage. I am suspicious that REM/Rate does not model the thermal bridging and mass features very well. Would I be better served performing this comparison in DOE-2 or would the results not be that much different?<o:p></o:p></SPAN></FONT></P></DIV></BODY></HTML>