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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>While I don’t intend to discuss the merits of VAV systems and know I’m part of a minority in that area, this is exactly why DOAS systems are being explored more right now on the research side (take for example the number of ASHRAE Journal articles on the topic over the past few years). Without seeing your OA calcs I would also agree that the difference is more than I would expect between the two systems, but I’m more inclined to think the DOAS might be a bit low if it is being used in conjunction with FCUs. VAV systems are typically underventilated due to two common mistakes in the calculations: not analyzing with the correct Ez and not using the minimum expected primary airflow for design purposes (refer to ASHRAE 62.1-2007 Section 6.2.5.1, specifically the note in that section). When fixing these two typical mistakes in calculations without optimizing the primary airflow rates, I typically see OA requirements double from the incorrectly calculated values.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>This situation is a good example of when to do one of two things (possibly both together)<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='color:#1F497D'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='color:#1F497D'>If this is a LEED project, submit a project-specific CIR<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='color:#1F497D'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='color:#1F497D'>Use section ASHRAE 90.1-2007 Section 2.5 Exceptional Calculation Methodology to get around the requirement and document the energy savings from reduced OA requirements for a DOAS system.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><b><span style='font-size:7.5pt;font-family:"Verdana","sans-serif";color:#1F497D'>Jeremy R. Poling, PE, LEED AP+BDC</span></b><span style='color:#1F497D'><br><br></span><span style='color:#1F497D'><o:p></o:p></span></p></div><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><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";color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> bldg-sim-bounces@lists.onebuilding.org [mailto:bldg-sim-bounces@lists.onebuilding.org] <b>On Behalf Of </b>Mark Sorensen<br><b>Sent:</b> Wednesday, August 17, 2011 11:42 AM<br><b>To:</b> bldg-sim@lists.onebuilding.org<br><b>Subject:</b> Re: [Bldg-sim] DOAS and baseline OA<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Anne,<br><br>While LEED/ASHRAE 90.1 requires the ventilation rates to be the same in both the Baseline and Proposed systems, the calculated difference for the two systems is much higher than expected. Suggest taking another look at the calculations and confirming that the critical zone for the VAV system has been properly determined and whether appropriate factors for the zone air distribution effectiveness (Ez) and system ventilation efficiency (Ev) have been applied.<br><br>Mark Sorensen<br>Diversified Energy Services<br>Fruitport, Michigan<br>231-578-1264<br><br>On 8/16/2011 9:12 AM, Jim Dirkes wrote: <o:p></o:p></p><p class=MsoNormal><span style='color:#1F497D'>Dear Anne,</span><o:p></o:p></p><p class=MsoNormal><span style='color:#1F497D'>I’m not sure why you think the OA requirement varies by system. I’m not well versed in Standard 62, but my basic understanding is that one of the calculation methods is the result of building area and number of occupants. Those are unchanged by system selection … which is why it makes sense for Appendix G to require matching volumes.</span><o:p></o:p></p><p class=MsoNormal><span style='color:#1F497D'> </span><o:p></o:p></p><div><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:13.5pt;color:#1F497D'>The Building Performance Team<br></span></b><b><span style='color:#1F497D'>James V. Dirkes II, P.E., BEMP , LEED AP<br></span></b><span style='color:#1F497D'>1631 Acacia Drive NW<br>Grand Rapids, MI 49504<br>616 450 8653</span><o:p></o:p></p></div><p class=MsoNormal><span style='color:#1F497D'> </span><o:p></o:p></p><div><div style='border:none;border-top:solid windowtext 1.0pt;padding:3.0pt 0in 0in 0in;border-color:-moz-use-text-color -moz-use-text-color'><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"'> <a href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a> [<a href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>] <b>On Behalf Of </b>Anne Juran<br><b>Sent:</b> Tuesday, August 16, 2011 8:33 AM<br><b>To:</b> <a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br><b>Subject:</b> [Bldg-sim] DOAS and baseline OA</span><o:p></o:p></p></div></div><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>I’m curious how everyone is handling the OA for Appendix G simulations when using a DOAS in the proposed system. We have a design that is DOAS + FCU with a total OA of 8,000 CFM. When you run the OA calcs for this same building with a VAV system (the baseline), the total OA required to meet Standard 62 is 39,000 CFM. This difference in OA represents a significant energy savings (in climate zone 4A), yet Appendix G requires the OA volumes to match. It does not seem “fair” to me that the proposed case cannot take credit for design choice when it comes to OA. I feel like Appendix G should make an exception for DOAS. Am I missing something? Is there a way around this? Any thoughts are appreciated!</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>Anne</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> </span><o:p></o:p></p><pre><o:p> </o:p></pre><pre><o:p> </o:p></pre><pre>_______________________________________________<o:p></o:p></pre><pre>Bldg-sim mailing list<o:p></o:p></pre><pre><a href="http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org</a><o:p></o:p></pre><pre>To unsubscribe from this mailing list send a blank message to <a href="mailto:BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG">BLDG-SIM-UNSUBSCRIBE@ONEBUILDING.ORG</a><o:p></o:p></pre><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p></div></body></html>