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<p class=MsoNormal><span style='color:#1F497D'>Sounds right to me.
I’ve wondered about the relatively low “U” for basements, too.
My best guess for ASHRAE’s rationale is that the additional heating load
is balanced by reduced cooling load……<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal align=center style='text-align:center'><b><span
style='font-size:13.5pt;font-family:"Times New Roman","serif";color:#1F497D'>The
Building Performance Team<br>
</span></b><b><span style='font-size:12.0pt;font-family:"Times New Roman","serif";
color:#1F497D'>James V. Dirkes II, P.E., LEED AP<br>
</span></b><span style='font-size:12.0pt;font-family:"Times New Roman","serif";
color:#1F497D'>1631 Acacia Drive NW<br>
Grand Rapids, MI 49504<br>
616 450 8653<o:p></o:p></span></p>
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<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b>On Behalf Of </b>James
Hansen<br>
<b>Sent:</b> Tuesday, March 30, 2010 8:18 AM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> [Bldg-sim] C-factors<o:p></o:p></span></p>
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<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>I wanted to run something by
everyone to see if this is how most people model underground
walls: <o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>For my climate zone (4A), the
required C-factor for Underground Wall is 1.140 (no U-value listed).<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>If you go to Appendix A of
90.1-2004, specifically sections A4.1 and Table A4.2, I *<b>think</b>* that you
come to the conclusion that the baseline underground walls should be modeled as
8 inch medium weight concrete block with a density of 115 lb/ft3, solid grouted
cores, and NO INSULATION. This is what A4.1 says, and the published
C-factors in Table A4.2 indicate that a C-factor of 1.140 is obtained using this
wall and no framing / no insulation.<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>If you then refer to Table A3.1C,
for that wall type, sure enough a C-factor of 1.140 is listed with a
corresponding U-value of 0.58.<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>When I run my baseline model with
an underground wall construction having a U-value of 0.58, I end up with way
more cooling hours and energy that my proposed model, which has R-13
insulation. This is presumably because those underground spaces are
constantly losing heat thru the poor wall construction to the 55 degree earth
heat sink (or whatever eQuest calculates it as).<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>I’m not complaining, as it
makes the proposed system look that much more efficient, but I just wanted to
double check that I’m doing this right.<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>On a side note, I’m having a
tough time reducing my unmet load hours for the underground VAV system, but
that’s besides the point…<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>Thanks!<o:p></o:p></p>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'><b><span style='font-family:"Arial","sans-serif";
color:teal'>GHT Limited<br>
</span></b><b><span style='font-family:"Arial","sans-serif"'><ns0:PersonName><span
style='color:black'>James Hansen</span></ns0:PersonName></span><span
style='color:black'>, PE, LEED AP<o:p></o:p></span></b></p>
<p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:10.0pt;
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