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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If you want to use Material:Air, then you
can get thermal resistance values for various air gap configurations from ASHRAE
Handbook of fundamentals, in HoF 2001 its Table 3 in Chapt 25. But these are
for sealed cavities, not ventilated. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>For an opaque exterior ventilated cavity,
there is also a special model in EnergyPlus – see the
Surface:HeatTransfer:ExteriorNaturalVentedCavity object. But that model isn’t
really intended for such a thick, heavy outer veneer. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> <st1:PersonName
w:st="on">BLDG-SIM@gard.com</st1:PersonName> [mailto:<st1:PersonName w:st="on">BLDG-SIM@gard.com</st1:PersonName>]
<b><span style='font-weight:bold'>On Behalf Of </span></b>Josh K<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, October 02, 2007
11:11 AM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">BLDG-SIM@gard.com</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> [BLDG-SIM] thermal
modeling of air cavity</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Hi all;<br>
<br>
I'm attempting to model a building that's facade has a ventilated 25mm air gap
between a 100mm brick veneer on the outer side and an EPS/steel stud
construction on the inside. I'm curious exactly how I should account for the
conductance/resistance of the air gap. This will obviously depend on the inner
and outer surface temperatures and the natural convection currents that results
from them, and further to that the outdoor wind speed; I'm wondering if anyone
is aware of any methods that have been developed to approximate the equivalent
thermal properties of an air gap in such a situation. <br>
<br>
The software that I'm using (EnergyPlus) allows one to specify an
"air" material object (Material:Air) to be used analogously with
conventional material objects (ie gypsum, EPS, etc) in forming wall
constructions. The only physical property that one can specify for the
Material:Air object is its thermal resistance in mē·K/W. Ultimately, what I'm
trying to figure out is the best way to specify this field. <br>
<br>
My thanks in advance for any assistance that may be offered to me on this
matter...<br>
<br>
Josh<br>
<br>
<br>
Josh Kjenner, EIT, LEED AP<br>
Manasc Isaac Architects Ltd.<br>
10225 100 Avenue :: <st1:place w:st="on"><st1:City w:st="on">Edmonton</st1:City>,
<st1:State w:st="on">AB</st1:State> <st1:PostalCode w:st="on">T5J 0A1</st1:PostalCode></st1:place><br>
780.429.3977<o:p></o:p></span></font></p>
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