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<p class=MsoNormal>I’m having a tough time deciphering how the USGBC
wants you to prove a 30% increase in OA (versus ASHRAE 62) for multi-zone
systems, and how this impacts the energy model for the proposed building.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>There is a very specific way to determine the volume of outside
air for a multi-zone system (VPR using the 62MZCalc spreadsheet). This
takes into account, among other things, room area, population, supply volume,
minimum primary air volume, efficiency of transfer air, system efficiency,
etc. Once you understand all of the variables, it’s fairly
straightforward to prove compliance with EQp1, and obtain the minimum OA intake
volume.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>However, EQc2 requires a 30% increase in outside air volume
for EACH zone “above the minimum rates required by ASHRAE Standard 62.1-2004
as determined by EQ Prerequisite 1”. Although I’ve received
USGBC comments before claiming that I have to prove that EACH zone has 30% more
OA than required by the VPR, can anyone <b><u>confirm for sure</u></b> if this
is the case for multi-zone systems?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>To give you an example:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’ve got a 33,000 square foot floor served by an
AHU. Standard office space with 3 or 4 conference rooms. I’ve
used the 62MZCalc spreadsheet, and determined that my AHU needs 3,800 CFM
OA. I’ve *<b>designed</b>* the system to provide 7,000 CFM.
Almost twice the amount of outside air as needed (I have DCV in place).
However, the critical conference room doesn’t get even the minimum
required OA. It doesn’t need to – that’s the whole
point of the Multizone calc, and a good reason to use series fan-powered
terminals.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Per the NCv2.2 Reference Guide, we are supposed to include
the actual OA volumes in the energy model, so I guess it’s important to get
this right, especially for those clients that request a 30% increase.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks in advance,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><b><span style='font-size:12.0pt;font-family:"Arial","sans-serif";
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</span></b><b><span style='font-family:"Arial","sans-serif"'><ns0:PersonName><span
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PE, LEED AP<o:p></o:p></span></b></p>
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