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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Jaigath,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Karen is right on. Lower window U-values and additional
insulation in walls and roofs can cause a net energy increase in buildings with
high internal heat gains. If you look at the month-by-month consumption, you
may see that the “better” envelope helps out in winter and summer,
but hurts in spring and fall. The overall net effect over the year is sometimes
negative.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>When the air outside is cooler than inside, then some of the
internal heat can get out of the building through the envelope. A more
insulated envelope slows the heat escaping through the envelope, so more of the
heat has to get out of the building through the HVAC system, resulting in more
cooling energy. If there is an economizer (“free cooling”), the
effect is not as severe the net effect of more insulation could be positive.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>________________________________</span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><ns0:PersonName><span
style='color:#1F497D'>Keith Swartz</span></ns0:PersonName><span
style='color:#1F497D'>, P.E., LEED AP</span></span><span style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'><br>
Energy Engineer / Senior Project Manager<br>
</span><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><ns0:PlaceName><span
style='color:#1F497D'>Energy</span></ns0:PlaceName><span style='color:#1F497D'>
</span><ns0:PlaceType><span style='color:#1F497D'>Center</span></ns0:PlaceType><span
style='color:#1F497D'> of </span><ns0:place><ns0:State><span style='color:#1F497D'>Wisconsin</span><span
style='color:#1F497D;font-weight:normal'><br>
</span><span style='font-weight:normal'></ns0:State></span></ns0:place></span></b><ns0:Street><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'><ns0:address><span
style='color:#1F497D'>455 Science Drive, Suite 200, </span></ns0:address></ns0:Street></span><ns0:place><span
style='font-size:10.0pt;font-family:"Arial","sans-serif"'><ns0:City><span
style='color:#1F497D'>Madison</span></ns0:City><span style='color:#1F497D'>, </span><ns0:State><span
style='color:#1F497D'>WI</span></ns0:State><span style='color:#1F497D'> </span><ns0:PostalCode><span
style='color:#1F497D'>53711<br>
</span></ns0:PostalCode></ns0:place></span><span style='font-size:10.0pt;
font-family:"Arial","sans-serif";color:#1F497D'>Phone: 608.238.8276 x123<br>
Fax: 608.238.0523<br>
<br>
</span><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>The Buildings Team</span></b><span style='color:#1F497D'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>Design decisions through energy, economics and emissions
analysis.</span></i><span style='color:#1F497D'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D'><a href="http://www.ecw.org/Buildings">www.ecw.org/Buildings</a>
<o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='color:#1F497D'><br>
</span><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><ns0:place><ns0:PlaceName><span
style='color:#1F497D'>Energy</span></ns0:PlaceName><span style='color:#1F497D'>
</span><ns0:PlaceType><span style='color:#1F497D'>Center</span></ns0:PlaceType><span
style='color:#1F497D'> </span><ns0:PlaceType><span style='color:#1F497D'>University<br>
</span></ns0:PlaceType></ns0:place></span></b><i><span style='font-size:10.0pt;
font-family:"Arial","sans-serif";color:#1F497D'>Your gateway to sustainable
design training and online education programs.<br>
</span></i><span style='color:#1F497D'><a href="http://www.ecw.org/university/"
title="http://www.ecw.org/university/"><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>www.ecw.org/university/</span></a></span><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><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"'> Karen Walkerman
[mailto:kwalkerman@gmail.com] <br>
<b>Sent:</b> Friday, September 24, 2010 6:15 AM<br>
<b>To:</b> Jaigath Chandraprakash<br>
<b>Cc:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] Unusual Result<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>If most of your cooling loads come from internal loads as
you said, then having windows with a higher U-value allows the building to lose
heat to the outside any time it is cooler outside than inside. If you
look at ASHRAE 90.1, the requirements for windows changes dramatically as you
move from colder to warmer zones. In warmer zones, the allowed U-value is
higher, but the SHGC is lower.<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>Also, it is usually good to verify that this is actually the
case, often installed equipment runs only a fraction of the day, or at a
fraction of the peak energy use. If your internal loads are not actually
as high as you are modeling, this could change things.<o:p></o:p></p>
</div>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>Lastly, does the building have an economizer? This may
make sense for this particular project.<o:p></o:p></p>
</div>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>--<o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'>Karen<o:p></o:p></p>
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<p class=MsoNormal>On Fri, Sep 24, 2010 at 5:59 AM, Jaigath Chandraprakash <<a
href="mailto:cjaigath@yahoo.com">cjaigath@yahoo.com</a>> wrote:<o:p></o:p></p>
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<p class=MsoNormal>The project I am working on is an office building that
operates 20 hrs per day with most of the loads occuring at night and low
occupancy on daytime. It is a cooled by a DX roof unit and has a very high
internal load. No heating equipment is required because the building is in
Climate 1. I was surprised that when I changed my window U-value from 0.3 to
0.7 I got less cooling consumption. I always thought that getting
low u-value will give me less coling consumption. Can somebody tell me why
I am getting less cooling when I use a higher window U-value?<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>Thanks,<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>Jaigath<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><br>
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