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    <p>Ismail,</p>
    <p>  Type56 assumes that zones have neutral pressure. If you add air
      to a zone, it is assumed that the same mass of air leaves the zone
      by some means. The same would be true if you were to actively
      extract air from the zone; more air would come in to replace the
      air that you extracted. The issue, I think, is where the air that
      comes into the zone comes from. If it comes from a humid source
      then the zone humidity is going to go up. If the air comes from a
      dry source then the zone humidity will go down. One of the
      challenges with natural ventilation is that if the building is
      cooler than the ambient when natural ventilation is activated then
      humid air comes into a cool space from outside and the RH in the
      space goes way up (cool air can hold less moisture than warm air).
      <br>
    </p>
    <p>kind regards,</p>
    <p> David</p>
    <p><br>
    </p>
    <br>
    <div class="moz-cite-prefix">On 07/10/2017 08:43, Issmail OUHALLOU
      via TRNSYS-users wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAA779b2O1NZb8NX3S9CZukw9qK78-yz-7oF8=kLD+1fabvi0EQ@mail.gmail.com">
      <div dir="ltr"><img class="mailtrack-img" alt=""
src="https://mailtrack.io/trace/mail/4e128a5852e66629b3be71dbca54ce3c3175576b.png?u=633613"
          moz-do-not-send="true" height="0" width="0">
        <div class="gmail_default"
          style="font-family:arial,helvetica,sans-serif;color:rgb(0,0,0)">
          <div class="gmail_default" style="font-size:12.8px">Dear
            colleagues,</div>
          <div class="gmail_default" style="font-size:12.8px"><br>
          </div>
          <div class="gmail_default" style="font-size:12.8px">I am
            trying to simulate the impact of natural ventilation by
            calculating the mean air velocity entering through the
            window (in m/s) according to the equation below:</div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000"><img
                src="cid:part2.4EE7FA73.178871F4@tess-inc.com"
                class="gmail-CToWUd" style="margin-right: 0px;"
                height="49" width="373"></font><br>
            <font face="arial, helvetica, sans-serif" color="#000000">​I
              got the results as shown in attached files before and
              after natural ventilation. The humidity has increased
              enormously !</font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000"><br>
            </font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000">I
              figure out that in TRNBuild the air cannot be extracted
              from the zone ! How can I extract the air from a zone
              after activating natural or mechanical ventilation ?</font><br>
          </div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000"><br>
            </font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000">Does
              anyone have experience to deal with such a problem ?</font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000"><br>
            </font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000">Thanks
              in advance,</font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000">Best</font></div>
          <div class="gmail_default"
style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px"><font
              face="arial, helvetica, sans-serif" color="#000000">Ismail</font></div>
        </div>
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        </div>
        -- <br>
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                                      <div dir="ltr"><i
style="font-size:10.6667px;color:rgb(0,0,0);font-family:Arial,sans-serif">************************************************</i></div>
                                      <div dir="ltr"><i
style="font-size:10.6667px;color:rgb(0,0,0);font-family:Arial,sans-serif">Ismail
                                          OUHALLOU</i><br>
                                      </div>
                                      <div dir="ltr">
                                        <div><font face="Arial,
                                            sans-serif" color="#000000"><span
style="font-size:10.6667px">Green building & Sustainability
                                              consultant</span></font></div>
                                        <div><br>
                                        </div>
                                        <div><font face="Arial,
                                            sans-serif" color="#000000"><span
style="font-size:10.6667px"><b>Morocco</b></span></font></div>
                                        <div><span
style="color:rgb(0,0,0);font-family:Arial,sans-serif;font-size:10.6667px">P:+212<b>
                                            </b>620<b> </b>548<b> </b>116</span></div>
                                        <div><font face="Arial,
                                            sans-serif" color="#000000"><span
style="font-size:10.6667px">F:+212<b> </b>522<b> </b>326<b> </b>440</span></font></div>
                                        <div><a
                                            href="mailto:i.ouhallou@trusted-energy.com"
                                            target="_blank"
                                            moz-do-not-send="true"><font
style="background-color:rgb(238,238,238)" size="1">i.ouhallou@trusted-energy.com</font></a><br>
                                        </div>
                                        <div><a
                                            href="mailto:issmail.ouhallou@gmail.com"
                                            target="_blank"
                                            moz-do-not-send="true"><font
style="background-color:rgb(238,238,238)" size="1">issmail.ouhallou@gmail.com</font></a><br>
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      <pre wrap="">_______________________________________________
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</pre>
    </blockquote>
    <br>
    <pre class="moz-signature" cols="72">-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
<a class="moz-txt-link-abbreviated" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>

<a class="moz-txt-link-freetext" href="http://www.tess-inc.com">http://www.tess-inc.com</a>
<a class="moz-txt-link-freetext" href="http://www.trnsys.com">http://www.trnsys.com</a></pre>
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