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<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>Keith,</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>For situation (1), exception (5) to
90.1-04 section 6.5.2.1 should provide relief.</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>The User's Manual explains the details and
gives an example that illuminates this.</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>I believe this is the rationale: moving to
100% OA system would greatly increase the energy usage of the project while over-ventilating
many zones. Therefore, increasing the supply air to selected critical zones can
be balanced against increasing the total ventilation air in order to produce an
optimized design somewhere between Constant Volume Reheat and 100% OA VAV.</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>For situation (2), ASHRAE 90.1 baselines may
not produce a design that complies with the ventilation code. The minimum ventilation
airflow for the baseline will be identical to the proposed case (G3.1.2.5), but
as you noted the VAV minimums may be different. I imagine this would penalize a
VAV system where larger "proposed case" minimums are required for 62 compliance.</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>This may be an area where an addendum
could allow some wiggle room similar to exception (5) to section 6.5.2.1.</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'>Aaron</span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:blue'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b>
bldg-sim-bounces@lists.onebuilding.org [mailto:bldg-sim-bounces@lists.onebuilding.org]
<b><span style='font-weight:bold'>On Behalf Of </span></b>Keith Swartz<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, February 11, 2008
10:54 AM<br>
<b><span style='font-weight:bold'>To:</span></b> bldg-sim@lists.onebuilding.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Bldg-sim] Ventilation
Problems in VAV Systems for LEED Model</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;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.</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;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?</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;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?</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;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? </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;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?</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Sincerely,</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Keith Swartz, PE, LEED® AP</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><ns0:PlaceName w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">Energy</ns0:PlaceName>
<ns0:PlaceType w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">Center</ns0:PlaceType>
of <ns0:place w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z"><ns0:State w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z"></span></font><font size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Wisconsin</ns0:State></ns0:place></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><ns0:Street w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z"><ns0:address w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">455
Science Drive</ns0:address></ns0:Street></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><ns0:address w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z"><ns0:Street w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">Suite</ns0:Street>
200</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><ns0:place w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z"><ns0:City w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">Madison</ns0:City>,
<ns0:State w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">WI</ns0:State>
<ns0:PostalCode w:insAuthor="Keith Swartz" w:insDate="2008-02-11T09:00:00Z" w:endInsAuthor="Keith Swartz" w:endInsDate="2008-02-11T09:00:00Z">53711</ns0:PostalCode></ns0:place></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Phone: 608-238-8276 ext. 123</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Fax: 608-238-0523</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><a href="http://www.ecw.org/">www.ecw.org</a></span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>The Energy Center of Wisconsin is an
independent, nonprofit organization that seeks solutions to energy challenges.</span></font></p>
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