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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hi,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>This isn’t quite a modeling question, but I figured
you all might have some insight.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am working on a new refrigerated warehouse that is under
construction in <st1:State w:st="on"><st1:place w:st="on">New Hampshire</st1:place></st1:State>.
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The roof assembly is basically a metal corrugated deck, on
top of which is R-50 of rigid foam insulation. The underside of the deck
is exposed to the refrigerated area. Roof anchors tie the rigid
insulation to the roof deck / joists. The rubber membrane roof is adhered
to the top of the foam insulation. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The owner asked whether it made sense to install an
additional layer of rigid insulation above the standard layers. The new
layer would raise the total assembly to R-63, and would be glued to the top
side of the standard insulation, so that the roof anchors would be embedded in
an insulation sandwich. We calculated minimal refrigeration savings from
the added R-value. However, the owner felt that sandwiching the metal
anchors in insulation would remove any threat of condensation and freezing below
the roof membrane where the anchors would potentially be cold enough to cause
this.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The owner said that on another building, the roof membrane
became separated at the location of the anchors, and they attributed it to the
cold spots, condensation, and freezing caused by the anchors and their conduit
into the cold space. Has anyone heard of such a
problem? At first glance, it would seem that on a hot day, the top end of
the metal anchor would be sufficiently warmed by the hot roof so as not to
cause any condensation or freezing at the membrane surface. In the
winter, the whole roof will be below freezing, so the extra insulation won’t
affect things relative to the anchor then. Is there another explanation
for the failed roofing that the owner described? Perhaps the penetration
of the anchors through the insulation is allowing moisture from the space to
migrate up to the roof membrane, and the moisture is trapped and then freezes
in the winter? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Any ideas appreciated, as always. Happy Memorial Day.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Sincerely,</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Alec Stevens, PE, LEED AP</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>DMI</span></font><o:p></o:p></p>
<p class=MsoNormal><st1:address w:st="on"><st1:Street w:st="on"><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>450 Lexington St.</span></font></st1:Street><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>, <st1:City
w:st="on">Newton</st1:City>, <st1:State w:st="on">MA</st1:State> <st1:PostalCode
w:st="on">02466</st1:PostalCode></span></font></st1:address><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>p: 617-527-1525 x105 f: 617-527-6606</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>e: astevens@dmiinc.com</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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