<div>Obtaining a negative pressure difference also requires sealing the space.  Door seals, and sealing walls.  If you exhaust 0.5 cfm/sf from a room with chicken wire walls, you won't achieve any kind of measurable pressure difference.<br>
</div><div><br></div><div>I usually steer clients away from this credit for this very reason (difficulty coupled with measurability)</div><div><br></div><div>--</div><div>Karen</div><br><div class="gmail_quote">On Wed, Oct 6, 2010 at 3:36 PM, James V Dirkes II, PE <span dir="ltr"><<a href="mailto:jvd2pe@tds.net">jvd2pe@tds.net</a>></span> wrote:<br>
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<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">Personal opinion:</span></p>

<p><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span>·<span style="font:7.0pt "Times New Roman"">        
</span></span></span><span style="font-size:11.0pt;color:#1F497D">5 Pa is difficult to (accurately) measure</span></p>

<p><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span>·<span style="font:7.0pt "Times New Roman"">        
</span></span></span><span style="font-size:11.0pt;color:#1F497D">1 Pa is impossible outside of a lab</span></p>

<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"> </span></p>

<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D">I don’t know what they were thinking when making these requirements,
since they’re not too clear, but I suspect that if you demonstrate .5cfm
/ sq.ft. and no recirculation you’ll be OK.</span></p>

<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"> </span></p>

<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"><img width="425" height="142"></span></p>

<p class="MsoNormal"><span style="font-size:11.0pt;color:#1F497D"> </span></p>

<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., LEED AP<br>
</span></b><span style="color:#1F497D">1631 Acacia Drive NW<br>
Grand Rapids, MI 49504<br>
616 450 8653</span></p>

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<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-size:10.0pt">From:</span></b><span style="font-size:10.0pt"> <a href="mailto:bldg-sim-bounces@lists.onebuilding.org" target="_blank">bldg-sim-bounces@lists.onebuilding.org</a>
[mailto:<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" target="_blank">bldg-sim-bounces@lists.onebuilding.org</a>] <b>On Behalf Of </b>Deepa<br>
<b>Sent:</b> Wednesday, October 06, 2010 2:59 PM<br>
<b>To:</b> Bldg-Sim<br>
<b>Subject:</b> [Bldg-sim] Negative pressure for EQ cr 5</span></p>

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<p class="MsoNormal" style="margin-left:.5in">Hello all,</p>

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<p class="MsoNormal" style="margin-left:.5in">One of the requirements for EQ
Credit 5 is to prove that the areas such as the janitor's closet need to be
negatively pressurized to a minimum of 5Pa when doors are closed and
1Pa when doors are open. Generally, in mechanical drawings, the cfm values are
mentioned for exhaust fans. </p>

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<p class="MsoNormal" style="margin-left:.5in">I wanted some insight as to how
this pressure difference information can be obtained for both cases. Is there a
straightforward calculation? </p>

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<p class="MsoNormal" style="margin-left:.5in"> </p>

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<p class="MsoNormal" style="margin-left:.5in">Thanks,</p>

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<p class="MsoNormal" style="margin-left:.5in">Deepa</p>

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