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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=812221816-11022008>I agree with your idea to manually override the supply
air quantities for some spaces to make the OSA ratio for your system be
less than one. We have done this on a LEED project and believe it is
acceptable as long as your supply air quantities (and system sizes) are the
same for your baseline and proposed. Good luck!</SPAN></FONT></DIV><!-- Converted from text/rtf format -->
<P><FONT face=Arial size=2>~Dawne Herrick, PE, LEED® AP</FONT> <BR><FONT
face=Arial size=2>Mechanical and Fire Protection Engineer</FONT> </P>
<P><B><FONT face=Arial color=#808000 size=2>CDi ENGINEERS</FONT></B> <BR><FONT
face=Arial size=2>(425) 672-1071</FONT> <BR><FONT face=Arial size=2><A
href="http://www.cdiengineers.com">www.cdiengineers.com</A></FONT>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> Keith Swartz [mailto:kswartz@ecw.org]
<BR><B>Sent:</B> Monday, February 11, 2008 7:54 AM<BR><B>To:</B>
bldg-sim@lists.onebuilding.org<BR><B>Subject:</B> [Bldg-sim] Ventilation
Problems in VAV Systems for LEED Model<BR></FONT><BR></P>
<DIV></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">I am having some difficulties
regarding ventilation in VAV systems for a LEED energy model that some of you
have probably encountered and would like your ideas regarding how to handle
them. I am using Trane TRACE v.6.1.2.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">1. ASHRAE 62.1-2004 requires some
ventilation in storage rooms – 0 cfm/person (because it is typically unoccupied)
and 0.12 cfm/sq ft (Table 6-1). I have a school with some internal storage rooms
(no envelope exposure). The only internal load is lighting. Even if I have the
lights on, the supply air needed is less than 0.12 cfm/sq ft, so the ventilation
fraction for the room is greater than one. The multiple space equation then
causes the entire VAV system to need 100% outside air. Then the baseline model
would need energy recovery…You see how far from reality this is
going?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">One idea I had to deal with it is to
manually override the supply air to some quantity above 0.12 cfm/sq ft instead
of using the calculated supply air flow, but I have a feeling that the LEED
evaluator would not look favorably on that. Perhaps it would be acceptable as
long as I did it the same in both the baseline and the proposed building. What
suggestions do you have for dealing with this?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">2. ASHRAE 90.1-2004 Appendix G
requires that the minimum volume setpoints for VAV reheat boxes to be 0.4 cfm/sq
ft for the baseline (G3.1.3.13). This also causes the same problem as above –
100% outside air for the system. Of course the minimum volume setpoints for the
proposed model would match the design, so it is only a problem for the baseline.
The critical rooms are not only storage rooms mentioned above, but other spaces
where the ventilation requirement exceeds the load demand, such as restrooms. I
have transfer air set up for each of these spaces. Is there some trick with
using transfer air to make it work out? <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">There were no interpretations for
90.1 that addressed this. The only related CIR I found from the USGBC was dated
2-2-07 with a ruling on 2-26-07 for a lab which states in part, “Alternately,
the project may opt to model the VAV system as energy neutral and use the design
minimum turn down ratios of the proposed design.” I take this to mean that I
could have the minimum settings in the baseline match the proposed, but I would
have to change the envelope and lighting for each room in the system to match
the baseline to make the system “energy neutral.” We would loose credit for the
lighting savings. There were other CIRs that stated that the 0.4 cfm/sq ft
minimum setting could be disregarded in spaces where pressures needed to be
maintained (laboratories, hospitals, etc.) Any
suggestions?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal
style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT face=Arial
size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Sincerely,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal
style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto"><FONT face=Arial
size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Keith Swartz, PE, LEED®
AP<o:p></o:p></SPAN></FONT></P>
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style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><ns0:PlaceName
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w:st="on"><st1:place
w:st="on">Wisconsin</st1:place></st1:State></ns0:State></ns0:place><o:p></o:p></SPAN></FONT></P>
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w:insDate="2008-02-11T09:00:00Z" w:insAuthor="Keith Swartz"><st1:Street
w:st="on"><st1:address w:st="on">455 Science
Drive</st1:address></st1:Street></ns0:address></ns0:Street><o:p></o:p></SPAN></FONT></P>
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200</ns0:address><o:p></o:p></SPAN></FONT></P>
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<ns0:State w:endInsDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz"
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w:endInsAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z"
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