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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The difference in energy consumption becomes especially apparent
when you have a shutoff VAV system with reheat (like I do with this particular
model). If, for example, a ground floor interior zone called for heating
after-hours because of heat loss thru the slab, and you only had one system for
the whole building that has to operate, the energy consumption is significantly
more than if you have a system for each floor.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If LEED gives you the option to use Addenda or not use Addenda,
then in my case, I would more than likely NOT choose to use it. As long as
this is acceptable, which it appears it is, I can take significant credit for
having multiple AHUs in lieu of a single RTU system.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>It sort of feels like cheating to do this, but ASHRAE is very
specific on how you are to model the Baseline building, and I’m not doing
anything “wrong”, per se, by using a single system for the Baseline building.
For what it’s worth, there are a lot of buildings that use package penthouse
AHUs…<o:p></o:p></span></p>
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style='color:black'>, PE, LEED AP<o:p></o:p></span></b></p>
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<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><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"'> George Hu
[mailto:george.hu@awe-e.com] <br>
<b>Sent:</b> Wednesday, December 10, 2008 1:20 PM<br>
<b>To:</b> 'Bill Talbert'; James Hansen; equest-users@lists.onebuilding.org<br>
<b>Subject:</b> RE: [Equest-users] FW: Number of systems required by 90.1?<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>It seems odd to me that 90.1-2007 requires the baseline building
to have one system per floor (system types 5, 6, 7 & 8).</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>These are all VAV systems, where you have individual VAV boxes
responding to different thermal zones. Why would different</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>number of AHU’s in this case make a difference in heating and cooling
energy consumption?</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>In terms of fan energy, however, different number of AHU’s may
make a difference. This is because 90.1 regulates</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>the fan brake horsepower, which is depending on the size of the
fan (Table G3.1.2.9, <20,000 cfm or >20,000 cfm).</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>For the same sized building, assuming the total supply
airflow being roughly the same independent of the number of </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>AHU’s used, each individual fan’s brake house power would be
different depending on its fan size, this may lead to </span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>different total fan energy consumption when you add all
individual fan energy up. For this reason, I would argue, it makes</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>more sense to keep the same number of AHU’s in the baseline case
as in the proposed design, for you would then be comparing</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'>“apple to apple”, because the fan sizes in the proposed design
would be “comparable” to those in the baseline case.</span><o:p></o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Arial","sans-serif";
color:#1F497D'> </span><o:p></o:p></p>
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<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>George
Hu, PE, LEED AP</span><o:p></o:p></p>
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style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>President</span><o:p></o:p></p>
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Air Water Energy Engineers, Inc.</span></b><o:p></o:p></p>
<p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>781.652.8688</span><o:p></o:p></p>
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style='font-size:10.0pt;font-family:"Arial","sans-serif";color:#17365D'>www.awe-e.com</span><o:p></o:p></p>
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