[Greenbuilding] Insulation Problems

Thu Nov 11 10:02:22 CST 2010

Hi Thomas,
I love the suggestion of taping the seams and taping the board to z bars.  With the air leakage to the outside eliminated that would bring us a lot closer to the r-10, and it would be a proper drainage plane.  My concerns are, what kind of tape and how does water escape if it does get in?  2" of xps has permeance of .55.  Will that allow vapor  to escape? What about bulk moisture?  Behind the xps is a liquid applied membrane that probably has a very low permeance, so it has to dry to the outside.  

Lastly, looking at the interior wall assembly, if the open cell foam has a perm rating of 8, and 1" of polyiso has a perm of 2.33, this could be a well insulated wall and will still dry to the inside.  Right?  Unless I'm missing something, we'd end up with about an R30 wall.  I'd be very happy with that.  What do you think?  

Thanks!

John

  ----- Original Message ----- 
  From: Thomas Lewis 
  To: J Messerschmidt 
  Sent: Thursday, November 11, 2010 6:47 AM
  Subject: Re: [Greenbuilding] Insulation Problems

        " The bronze would be attached to the z bars."

        wait, is the cladding up?  
        if not, be sure to tape all seams and to the z bars, caulk small spaces and foam larger ones.
        If it can be incorporated, use home slicker behind the cladding with some screen wrapped around the edges that bugs could enter.

        "Time makes more converts than reason." Thomas Paine, Common Sense

        --- On Wed, 11/10/10, J Messerschmidt <John at fourpointscg.com> wrote:

          From: J Messerschmidt <John at fourpointscg.com>
          Subject: Re: [Greenbuilding] Insulation Problems
          To: "JOHN SALMEN" <terrain at shaw.ca>, "'Greenbuilding'" <greenbuilding at lists.bioenergylists.org>
          Date: Wednesday, November 10, 2010, 10:05 AM

          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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