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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>There are a couple of basic considerations that to be kept in
mind. <o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Adding the insulation to the exterior increases the temperature
of the sheathing so technically reduces the risk of condensation depending on
weather (and interior air leakage which is the big concern)<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
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</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Adding insulation reduces the ability for a wall to dry to the
exterior so the wall needs to have the ability to dry to the interior (existing
vb may be a problem)<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span
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</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Any potential for condensation in our climate is primarily a
result of interior air leakage during heating season so an interior air barrier
is crucial (caulk sealing, electrical gaskets, etc.)<o:p></o:p></span></p>
<p class=MsoListParagraph><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoListParagraph><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I prefer eps boards which you can get in full 4’x8’
- type 1 is about 4 per inch and type 2 a little higher (4.5?)<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><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> greenbuilding-bounces@lists.bioenergylists.org
[mailto:greenbuilding-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Chris
Koehn<br>
<b>Sent:</b> March 21, 2011 11:55 AM<br>
<b>To:</b> greenbuilding@lists.bioenergylists.org<br>
<b>Subject:</b> [Greenbuilding] exulation<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am planning some work on a 1970's single storey home here
on Vancouver Island. Replacing windows is the impetus. The home has vertical
cedar channel siding over tar paper over sheathing (both ply and solid sawn
recycled form wood in different areas) over 2X4 framing with fiberglass batt
insulation, over 6 mil poly vapor barrier over GWB. We are in zone 4C,
"mixed marine" with roughly 5400 f HDD. Our heating season is long
but rarely severe. <<a
href="http://www.greenbuildingadvisor.com/sites/default/files/H-T%20Zones%20-%20legend.jpg">http://www.greenbuildingadvisor.com/sites/default/files/H-T%20Zones%20-%20legend.jpg</a>><o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>I'm considering removing exterior siding and adding a layer
of rigid insulation while I'm at it. Some siding needs to be removed anyway for
window replacement and some in other areas needs to be replaced due to flicker
damage, so taking it all off (and re-using it) doesn't seem to me to be a
substantial added burden. <o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>Quoting the U.S. DOE site: "<span
class=apple-style-span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:#3C4349'>Foam board insulation is commonly placed between the exterior
finish (i.e., siding, brick) and the studs of exterior walls. To prevent air
infiltration, you should place rigid insulation boards tightly together and
seal the seams with tape or caulk. However, this practice may worry some
builders in cold climates since the foam board may act as a second vapor
diffusion retarder. Studies have shown, however, that condensation rarely
occurs in these areas unless something else is seriously wrong with the wall
assembly (i.e., massive uncontrolled air leakage into the walls from the
house). If the assembly is constructed correctly, the inside surface of the
foam board stays warm enough to keep water vapor in its gaseous state long
enough for it to escape."</span></span><o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>In the few areas I have opened the walls up I have seen no
evidence of condensation, though in some areas near the top plate some of the
insulation has turned grey, indicating air moving through it. It is possible, I
suppose, the air that's moving through the wall is not coming from the inside.<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>My questions to the group are:<o:p></o:p></p>
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<p class=MsoNormal>* Given our climate and wall profile, is adding insulation
to the outside a good idea? <o:p></o:p></p>
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<p class=MsoNormal>* Is there a type of insulation recommended for this work,
specifically in light of any concerns over moisture drive, as well as a desire
by the client to keep the thickness build-up minimal, and of course cost.<o:p></o:p></p>
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<p class=MsoNormal>* What are suggestions around detailing: joints between
insulation panels, treatments at the bottom (siding currently laps directly
over brick, which is applied to a concrete foundation), fastening schedules
(insulation and siding), drainage plane. The house has min. 2' overhangs. <o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>Thanks as always,<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>Chris Koehn<o:p></o:p></p>
</div>
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<p class=MsoNormal>TimberGuides<o:p></o:p></p>
</div>
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<p class=MsoNormal>Cobble Hill, BC<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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