[Greenbuilding] Insulation Problems

[J Messerschmidt]

John,
Thanks to your excellent  feedback and others, I can be more specific and 
narrow down the solutions.  The Dow insulation is the blue board.  The 
liquid coating is yellow and I don't know what that is.  The insulation, 
stated as r-10 is not continuous as it is cut every 24" by the continuous z 
bars running horizontally across the all the exterior walls. Yes, there are 
small gaps wherever the foam board butts up against the z bar, and where 
wherever there are seams.  The foam board is attached to the sheathing with 
nails and huge washers.  The bronze would be attached to the z bars. 
Apparently, a drainage plane was not intentionally planned when they 
designed it, but vapor and bulk moisture can eventually find its way 
out, -and not in- to the wall assembly.  Not the ideal scenario, but nothing 
to worry about.  What I'm getting here is that the r-10 is in reality an r-0 
or something close to that.

For the interior, I understand that the open cell could give us a whole wall 
r-value of about 15 and the 1" eps could add another 4 without fear of 
moisture being trapped, and not counting any windows.  The main benefit here 
would be to stop air infiltration inside the wall cavity.

Would this statement be accurate?

We are adding HRV and the A/C will most likely be on during the summer, 
barring any vacations etc.  Oh yeah, it's not in Queens, it's actually 
Brooklyn.  Being a snobby Manhattanite, I've never felt it necessary to 
cross the East River, so it's like a foreign country to me.  Thank God they 
speak English.


John



----- Original Message ----- 
From: "JOHN SALMEN" <terrain at shaw.ca>
To: "'J Messerschmidt'" <John at fourpointscg.com>; "'Greenbuilding'" 
<greenbuilding at lists.bioenergylists.org>
Sent: Wednesday, November 10, 2010 2:27 AM
Subject: RE: [Greenbuilding] Insulation Problems


> Bit confusing. Lot of different wall assemblies out there.
>
> The 2 inches of xps would be classed as semi-impermeable something around 
> .5
> perm.
> The liquid coating on the sheathing is probably comparable and the ply 
> would
> be at about 1 perm.
>
> So drying to the exterior is fairly limited. Recommendations for colder
> climates because of interior humidity would be to have more permeable
> materials to the exterior but the real issues are moisture tolerance of
> materials and moisture - sources of moisture and potential for drying.
>
> The ply is good in that it can be subject to extreme moisture loading and
> dry out if it has the opportunity. Framing less so.
>
> Open cell foam in the interior cavity would have a high perm rating (about 
> 8
> for the 6"?). A 1" interior eps board would be about 5 perm. So the wall 
> is
> basically drying to the interior.
>
> Interior moisture is then the issue as well as all the worpersonlike 
> details
> that will prevent moisture from getting in over x number of years. Using a
> spray foam is pretty affective for an air barrier and an interior board
> allows you to potentially create an even better air barrier with decent 
> perm
> (than trying to seal studs or gaps in the spray foam) to limit moisture
> laden air if detailed properly...
>
> Next issue and probably the most important one would be interior
> ventilation/dehumidification if the wall is to dry to the interior. I
> remember it gets pretty muggy in queens. I modelled a similar wall with 
> high
> interior humidity levels and it didn't look good.
>
> As for drainage plane and thermal values. The cladding I'm assuming mounts
> to the horizontal z clips and there is probably some small gap between the
> panels and the foam and between the foam and the gooped pywood and that
> probably be sufficient as I can't see any materials being compromised 
> other
> than the metal clips (if they are clips and not a continuous z bar). If 
> the
> clips corrode the panels fall off.
>
> I would include the 2" of foam in the thermal (what else is it doing?). 
> Hard
> to calculate the bridging from the clips and I don't think leeds is that
> critical at this point.
>
> I think the 1" interior if done in eps would be very useful for bridging
> thermal gaps adding significantly to the thermal value - and completing a
> sealed interior as an air barrier if done well.
>
> I have to say I am personally getting more fond of chopped straw and mud - 
> a
> little more physical activity and fewer spreadsheets and when it fails you
> just have a bunch of mud and straw.
>
>
>
>
> JOHN SALMEN ENVIRONMENTAL DESIGN
> 4465 UPHILL RD,. DUNCAN, B.C.  CANADA, V9L 6M7
> PH 250 748 7672 FAX 250 748 7612 CELL 250 246 8541
> terrain at shaw.ca
>
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