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<p class="MsoNormal">You can search the archives for the thread titled “Slab on Grade Floor Heat Loss” but here is how I personally handle F-factor to U-factor conversions:
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><i>In the past I’ve done a conversion of F-factor (perimeter based) slab-on-grade heat loss to U-factor (area) and input that in on a zone-by-zone basis if I really wanted to nail down SOG heat loss.
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<p class="MsoNormal"><i><o:p> </o:p></i></p>
<p class="MsoNormal"><i>Example- Space is 20’ x 30’, but the exposed perimeter is only two of the faces (20’ + 30’). Let’s say it is uninsulated SOG.
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<p class="MsoNormal"><i>F-factor from 90.1: F = 0.73 Btu/(hr*ft*F)<br>
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Perimeter based heat loss: 0.73 Btu/(hr*ft*F) * 50 ft = 36.5 BTU/(hr *F)<o:p></o:p></i></p>
<p class="MsoNormal"><i><o:p> </o:p></i></p>
<p class="MsoNormal"><i>Then we can back-calculate the U-factor to assume for the whole floor to equate to that heat loss: 36.5 BTU/(hr *F) = 600 SF * X BTU/(hr*SF*F) -> U = 0.0608 BTU/(hr*SF*F)<o:p></o:p></i></p>
<p class="MsoNormal"><i><o:p> </o:p></i></p>
<p class="MsoNormal"><i>You can create a custom floor construction for each space to provide the U-factor to produce equivalent heat loss that the F-factor calcs are telling you lose. For purely core zones (no exposed perimeter), I guess the F-factor calcs
are telling us were not really losing heat through that slab (doesn’t’ seem right, but it probably is relatively small) .<o:p></o:p></i></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#632423">Nathan Miller, PE, LEED AP BD+C –
</span></b><i><span style="font-size:8.0pt;font-family:"Verdana",sans-serif;color:black">Mechanical Engineer/Senior Energy Analyst</span></i><b><span style="font-size:9.0pt;font-family:"Verdana",sans-serif;color:#632423"><o:p></o:p></span></b></p>
<p class="MsoNormal" style="margin-top:3.0pt;line-height:115%"><b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#632423">RUSHING</span></b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#BFAB7F">
</span><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:black">|</span><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#BFAB7F">
</span><b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#632423">O</span></b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#A50021">
</span><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:black">206-285-7100 |</span><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#BFAB7F">
</span><b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#632423">C</span></b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#A50021">
</span><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:black">207-650-3942</span><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#BFAB7F"><o:p></o:p></span></p>
<p class="MsoNormal" style="line-height:115%"><b><span style="font-size:8.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#632423"><a href="http://www.rushingco.com/"><span style="color:#632423">www.rushingco.com</span></a></span></b><b><span style="font-size:9.0pt;line-height:115%;font-family:"Verdana",sans-serif;color:#632423"><o:p></o:p></span></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>From:</b> Equest-users <equest-users-bounces@lists.onebuilding.org>
<b>On Behalf Of </b>Konstantina Kalliakoudi via Equest-users<br>
<b>Sent:</b> Tuesday, July 23, 2019 7:18 AM<br>
<b>To:</b> equest-users@lists.onebuilding.org<br>
<b>Subject:</b> [Equest-users] Floors F- factor to Uvalue for equest input<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Dear equest users,<o:p></o:p></p>
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<p class="MsoNormal">I am using equest for LEED projects.<o:p></o:p></p>
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<p class="MsoNormal">In table 5.5-1of ASHRAE 90.1-2010 the F factor is given for floors.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">How can F- factor be used in order to get Uvalue, which is needed in equest for floors?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thank you<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Konstantina Kalliakoudi<o:p></o:p></p>
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<p class="MsoNormal">Mechanical Engineer Μ.Sc.<o:p></o:p></p>
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<p class="MsoNormal"><a href="http://www.khmoe.gr/" target="_blank">www.khmoe.gr</a><o:p></o:p></p>
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