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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Dear Vinay,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I’m not sure of the rationale for the ASHRAE 90.1
oversizing requirements, however here are my thoughts:<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:Symbol;color:#1F497D'><span
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</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I think the principal engineering rationale for oversizing is to
allow a building to reach its setpoint temperature quickly after a period of
inactivity. As an example, if a building is inactive during a holiday and
the temperature is allowed to float several degrees lower (in winter), the
additional 25% heating capacity will enable faster return to the normal
setpoint temperature. Steam heating systems can need even more capacity
for proper warmup capacity.<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:Symbol;color:#1F497D'><span
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</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Oversizing is also a common practice as a “safety factor”.
Most load calculation software even has a separate input for adding this “safety
factor”. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></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<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal style='margin-left:.5in'><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"'> bldg-sim-bounces@lists.onebuilding.org
[mailto:bldg-sim-bounces@lists.onebuilding.org] <b>On Behalf Of </b>Vinay
Devanathan<br>
<b>Sent:</b> Wednesday, June 23, 2010 10:00 AM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> [Bldg-sim] sizing for baseline case acc to App. G<o:p></o:p></span></p>
</div>
<p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p>
<p class=MsoNormal style='margin-left:.5in'>Hello All,<br>
<br>
Just to clarify a point - <br>
<br>
What does the oversizing of capacities by 15% for cooling and 25% for heating
exactly mean? Do we only size the cooling and heating capacity or also increase
the airflow rate corresponding to the oversizing?<br>
<br>
Thank you.<o:p></o:p></p>
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