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Old 04-26-2011, 05:36 PM   #46
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Replace 2x4 with 2x6 walls


SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation. BIBS is effective though you will need a poly or other v.b. inside for best results. SPF directly on OSB without either a rainscreen or v.b. is asking for problems. http://www.nrc-cnrc.gc.ca/eng/ibp/ir.../ctus-n32.html

http://www.buildingscience.com/docum...d%20in%20walls

Click on “G”- Conclusions; http://www.buildingphysics.umn.edu/CTteardown01/default.htm#A



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Old 04-26-2011, 05:43 PM   #47
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Quote:
Originally Posted by GBR in WA View Post
SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation. BIBS is effective though you will need a poly or other v.b. inside for best results. SPF directly on OSB without either a rainscreen or v.b. is asking for problems. http://www.nrc-cnrc.gc.ca/eng/ibp/ir.../ctus-n32.html

http://www.buildingscience.com/docum...d%20in%20walls

Click on “G”- Conclusions; http://www.buildingphysics.umn.edu/CTteardown01/default.htm#A



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Not sure what SPF is.
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Old 04-26-2011, 06:07 PM   #48
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Replace 2x4 with 2x6 walls


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Originally Posted by jackpine
Not sure what SPF is.
I think SPF is spray foam, don't know what BIBS is...
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Old 04-26-2011, 06:35 PM   #49
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Replace 2x4 with 2x6 walls


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Originally Posted by GBR in WA View Post
SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation. BIBS is effective though you will need a poly or other v.b. inside for best results. SPF directly on OSB without either a rainscreen or v.b. is asking for problems. http://www.nrc-cnrc.gc.ca/eng/ibp/ir.../ctus-n32.html

http://www.buildingscience.com/docum...d%20in%20walls

Click on “G”- Conclusions; http://www.buildingphysics.umn.edu/CTteardown01/default.htm#A



Gary



That's interesting, i've never heard of the 8''s before. I'm sure i've seen it sprayed on the job with 2x4 and 2x6 walls, no vb needed.

Could vary from area to area, i'm not a big fan of the vapour barrier anyways.
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Old 07-06-2011, 06:20 AM   #50
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Replace 2x4 with 2x6 walls


Time has come, work load small enough now and the weather is going to cooperate. Started tearing stuff down yesterday and the big wall will be installed this weekend. I will get some photos up for you all to watch me.
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Old 07-14-2011, 10:18 AM   #51
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Project is nearly complete. One question. Can i screw windows to the jam through the shims or just rely on the nailed flanges to hold it in place?
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Old 07-14-2011, 10:41 AM   #52
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Originally Posted by GBR in WA View Post
SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation.
This is a false statement. There are a variety of spray foam mixes with a varying level of permeability. The closed-cell Icynene MD-C-200 (2 lbs mix) is considered a vapor barrier at only 2". If you go with the open-cell formula then the thickness required to become a vapor barrier increases.
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Old 07-16-2011, 08:42 PM   #53
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You may be confusing vapor retarders with vapor barriers. Icynene C-200 is a retarder until +12" thick, then it's a vapor barrier.
http://www.icynene.com/assets/docume...t-Specs-US.pdf

You can spray a coating on SPF if you need the vapor barrier capabilities: in a cold climate: http://www.icynene.com/vapor-barriers/

I’m talking about a true vapor barrier, not retarder. From Building Science: “A vapor retarder is defined as follows:
Vapor Retarder*: The element that is designed and installed in an assembly to retard the movement of water by vapor diffusion.
The unit of measurement typically used in characterizing the water vapor permeance of materials is the “perm.” Several classes of vapor retarders are further defined as follows [4]:
· Class I Vapor Retarder: 0.1 perm or less
· Class II Vapor Retarder: 1.0 perm or less and greater than 0.1 perm
· Class III Vapor Retarder: 10 perm or less and greater than 1.0 perm
· Test Procedure for vapor retarders: ASTM E-96 Test Method A (the desiccant method or dry cup method)
Finally, a vapor barrier is defined as:
  • Vapor Barrier: A Class I vapor retarder.”
http://www.buildingscience.com/docum...gs?full_view=1
Which the latest IRC copies: http://publicecodes.citation.com/ico...001_par005.htm
Vapor retarder, not barrier: http://www.sprayfoam.com/mnps/fullth...id=5&startat=1

All in the terminology: http://www.greenbuildingadvisor.com/...vapor-barriers

Good read: http://www.buildingscience.com/docum...nd-wall-design




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Old 07-18-2011, 07:55 AM   #54
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Originally Posted by GBR in WA View Post
You may be confusing vapor retarders with vapor barriers. Icynene C-200 is a retarder until +12" thick, then it's a vapor barrier.
There is certainly an eternal debate about what is and isn't a "vapor barrier". To a scientist a vapor barrier is an impermeable substrate (aka 0.0 perms). To a building official a vapor barrier is a substrate with <1.0 perm. While the latter is technically a vapor retarder, for the functional reality of building <1.0 perm is essentially a vapor barrier.

The different classes for vapor retarders you listed is correct. The 2009 IBC section 1405.3 requires a class I or class II, which is <1 perm. Icynene MD-C-200 is 0.9 perms at 1.5". Most contractors spray in 1" increments, so 2" of Icynene MD-C-200 is considered a "vapor barrier" by the building officials.

Last edited by AGWhitehouse; 07-18-2011 at 03:22 PM. Reason: Clarification of points
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Old 07-18-2011, 09:13 AM   #55
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The IBC calls a vapor barrier as anything with 1 perm or less. Read the Icynene cut...it is 0.9 perms at 1.5". Most contractors spray in 1" increments, so 2" of Icynene MD-C-200 is considered a vapor barrier by the building code. Scientists may argue otherwise when analyzing against the galaxy, but code officials could care less.
I am not spraying insulation, putting in fiberglass batting. Cedar siding, 30lb felt, 1/2 inch OSB, poly, sheetrock. Thats the plan. I can't afford spray foam.
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Old 07-18-2011, 03:24 PM   #56
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I am not spraying insulation, putting in fiberglass batting. Cedar siding, 30lb felt, 1/2 inch OSB, poly, sheetrock. Thats the plan. I can't afford spray foam.
Good plan, I personally don't like spray foam...just clarying information about it.
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Old 07-20-2011, 10:51 PM   #57
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For those interested in vapor barriers/retarders, Icy is a Class 2, semi-impermeable foam with a perm rating of 1.35 per inch thickness (a little less than rigid foam board).
When doubling the thickness, 1/2 the perm rating;

1.35 =1" 0.68= 2" (less than faced f.g.insulation) 0.34= 4" (close to plywood) 0.17= 6" (still semi-impermeable Class 2)

and 0.084= 12" a vapor barrier. If you live in Alaska or Canada and if they require a Class 1 (impermeable) v.b., you need to cover the foam with a v.b. coating or spray 12" thick...... http://www.icynene.com/vapor-barriers/

Research to understand better; http://www.buildingscience.com/docum...vapor-barriers

http://www.dyplastproducts.com/water..._permeance.htm

http://www.buildingscience.com/docum...apor-retarders

http://www.buildingscience.com/docum...l-in-buildings


jackpine, have you sided already? One problem is cedar wicks water, use two layers of paper for better protection. I would use foam board outside to raise the dew point temperature of the OSB, and not use poly inside, rather faced insulation or a “smart vapor retarder”, pp #18-20 for North of you at International Falls; http://www.buildingscience.com/docum...nd-wall-design

http://www.forestprod.org/woodprotection06tsongas.pdf

http://www.allcityimprovements.com/r.../airspace.html
Granted, stucco here, though good for possible exterior leaks; http://www.energy.wsu.edu/ftp-ep/pub...importance.pdf

How will you be flashing the windows- top and bottom?

Have you seen “rain screen”?

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Old 07-21-2011, 06:28 AM   #58
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I have not yet sided, it is prepped with one layer of 30lb felt. Normal window flashing tape. I put it on over the felt already, but it is peeling off so will have to re do it before I side. Plan on siding in early August.

I would consider two layers of felt and the faced insulation and no poly if I knew why, but no rain screen. I looked into it and nobody is doing it, most never heard of it.
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Old 07-21-2011, 08:09 AM   #59
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Icy is a Class 2, semi-impermeable foam with a perm rating of 1.35 per inch thickness (a little less than rigid foam board).
Which specific Icynene product do you speak of?
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Last edited by AGWhitehouse; 07-21-2011 at 08:13 AM.
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Old 07-21-2011, 02:54 PM   #60
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C-200, the first one sited in post #53, supplied by you.

Not a vapor barrier; http://www.sprayfoam.com/mnps/fullth...id=5&startat=1


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