<div dir="ltr">makes me wonder how Prof. Kissock's formula compares with PHPP's formula. FWIW, PHPP offers some options for different thermal conductivity values according to soil types. <div><br></div><div>On a current project, I had changed the PHPP default (.07 hr ft^2/BTU in) to .52, a median value for clay-loam--the condition indicated on my soil map. that simple change dropped the annual heat demand from 4.75 kBtu's/SF/year down to 4.24 -- a dramatic reduction which would have otherwise permitted thinner subslab insulation (or some other similar modification). <br>
<br>but the PHIUS certifier did not accept the change, and insisted on using the default value.<br><br>AA</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Aug 24, 2013 at 5:44 AM, nick pine <span dir="ltr"><<a href="mailto:nick@early.com" target="_blank">nick@early.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">RT <<a href="mailto:archilogic@yahoo.ca" target="_blank">archilogic@yahoo.ca</a>> writes:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
... In putting our pants back on frontwards, someone noticed that we had all received tattoos onto our backsides:<br>
<br>
? ? ? ? ? "? q? =? A [ dT ( K/s + hc ) +? ( ? * T^4 ) ]? "<br>
</blockquote>
<br>
How do you estimate slab heat loss?<br>
<br>
After lots of finite difference network ground loss calculations Professor Kelly Kissock at U Dayton <a href="http://academic.udayton.edu/kissock/http/EEB/Energy%20Efficient%20Buildings_1.htm" target="_blank">http://academic.udayton.edu/<u></u>kissock/http/EEB/Energy%<u></u>20Efficient%20Buildings_1.htm</a> says an A ft^2 slab on US Rf foamboard with Rp vertical perimeter insulation down "to the footer" would have an approximate A(0.1140/(4+Rf+Rp)+0.8768/(16+<u></u>Rp)) Btu/h-F conductance from the room air temp to the 4 meter deep ground temp.<br>
<br>
For example, a 900 ft^2 slab on R10 foamboard with R15 perimeter insulation would have a 900(0.1140/(4+10+15)+0.8768/(<u></u>16+15)) = 29 Btu/h-F conductance from a 65 F room air temp to a 58 F deep ground temp, so the room would lose (65-58)29 = 203 Btu/h to the slab.<br>
<br>
How much would this change with different perimeter insulation depths?<br>
<br>
Nick <br>
<br>
______________________________<u></u>_________________<br>
Greenbuilding mailing list<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:Greenbuilding@bioenergylists.org" target="_blank">Greenbuilding@bioenergylists.<u></u>org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.<u></u>org/mailman/listinfo/<u></u>greenbuilding_lists.<u></u>bioenergylists.org</a><br>
<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br><font><font><span style="color:rgb(102,0,0)">Alan Abrams</span></font><b style="color:rgb(102,0,0)"><br></b><i><span style="color:rgb(102,102,102)">certified professional building designer, AIBD<br>
certified passive house consultant, PHIUS</span></i></font><div><i><span style="color:rgb(102,102,102)">certified passive house builder, PHIUS</span></i><font><span style="color:rgb(102,0,0)"><font color="#666666"><i><br>
</i></font></span><font><span style="color:rgb(102,0,0)">Abrams Design Build LLC</span></font><font size="4"><br style="color:rgb(102,0,0)"><font><i style="color:rgb(102,0,0)">sustainable design for <font>intentional</font> living</i></font></font></font><font style="color:rgb(102,102,102)" size="1"><font><br>
</font></font><font style="color:rgb(102,102,102)" size="1"><font>cell </font></font><font style="color:rgb(102,102,102)" size="1"><font>202-437-8583</font></font><font style="color:rgb(102,102,102)" size="1"><font><br>
<a style="color:rgb(102,102,102)" href="mailto:alan@abramsdesignbuild.com" target="_blank">alan@abramsdesignbuild.com</a><br style="color:rgb(102,102,102)">
<a style="color:rgb(102,102,102)" href="http://www.abramsdesignbuild.com/" target="_blank">www.abramsdesignbuild.com</a></font></font><br></div>
</div>