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Old 01-28-2013, 04:12 PM   #31
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If you added that (MA has it's own energy code, or similar, as I would have said) to the discussion at the appropriate time rather than the way you delivered it (two posts accusing me of not following code without an explanation), I could understand your two posts better; but, everyone is different. I was thinking the paper-faced was required per IRC all along (and glad you mentioned it), not even remembering that MA had their own code, rather than prescriptive. We have our own code here, also, much more strict in certain things. Hence the reason I usually say "check with your local AHJ" as you have seen many times before. The links I supplied are showing the vapor retarder (code required) is fine to use with foamboard toward the outside. But not the permanence ratings, as you said. We all need a "check locally" --- unless one checks each members residence/local code/local amendments to prescriptive codes. The science is accurate (IMO) and we will be seeing more states changing their views on what is now written as code, in the near future. Dept. of Energy has used BSC for many of their guidelines as you have seen. The "Build America" series is an example. The codes are slowly catching up to the science. We can advise members "how to" insulate/tile/build/etc. but it is up to them to get required permit, engineering, etc. All members (including moderators) advice comes with a warning; "There are no warranties, either expressed or implied, that the information on this website is accurate and reliable." found under "Terms of service" at bottom of every page.
"Massachussetts code (A zone 5 state) it states that the exterior "barrier" must be 10x more permeable than the interior "barrier"." if you would, give me a link to that please?

Gary

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Old 01-28-2013, 05:30 PM   #32
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Well, I have searched for that to no avail, must be looking in the wrong places. I found; MA is under 2009 IECC with amendments; http://www.reedconstructiondata.com/...massachusetts/

The amendments don't apply to this discussion, unless I missed it; http://www.mass.gov/eopss/consumer-p...base-code.html

Amendment of air barrier, but not perm ratings; pp.3,4; http://www.mass.gov/eopss/docs/dps/8...efficiency.pdf

Where did you find that at, could you post a link?

Gary
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Old 01-28-2013, 06:08 PM   #33
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Quite the first thread, seems I have found a bunch of good info and hit a nerve, appreciate the input both of you have given. I will be looking into MN's code before going forward (still demolishing) and making a decision from there.
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Old 01-28-2013, 06:51 PM   #34
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Gary, I've never doubted the science and it's future implications on building practices/code. I just ask that you state that it may NOT be code compliant right along with your suggestions. Buildingscience.com is the study for future code suggestions, not actually current lawful code. You and I know not to take what is typed here and directly apply it without the right approvals/permits, but many don't. They very well might read these posts (may not even be the OP, just a random googler) and apply the methods in real world scenarios, only to find out none of it is code worthy. That's all...

I'll look for that code piece tomorrow, don't have the books now...
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Old 01-28-2013, 09:41 PM   #35
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Originally Posted by quackaddict View Post
Quite the first thread, seems I have found a bunch of good info and hit a nerve, appreciate the input both of you have given. I will be looking into MN's code before going forward (still demolishing) and making a decision from there.
--------------------------------------------- have any more questions, you know where we are....

Gary
PS. let us know what the inspector says...
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Old 01-29-2013, 12:38 PM   #36
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Turns out the MA job I did where that code section was applicable was long ago enough to be within the expired version of the MA Building Code. They now follow IBC 2009 with amendments. Anywho, here's the section:

Excerpt from the Massachussetts Commerical State Building Code 780 CMR - Seventh Edition (Effective 9/1/08):

"1304.1.2 Moisture Control. The design of buildings for energy conservation shall not create conditions of accelerated deterioration from moisture condensation.
A vapor retarder shall be installed on the winter warm side of walls, ceilings and floors enclosing a conditioned space. Batt/blanket insulation with a vapor retarder attached shall be attached to the winter warm sides or faces of the wall studs, sole plates, top plates, lintels and headers at intervals of eight inches on center to prevent convection loops through the insulation. Where batt/blanket insulation is of a "friction fit" design and a sheet vapor retarder is employed, the vapor retarder shall be affixed to the interior face of the wall studs, sole plates, top plates, lintels and headers winter warm side in accordance with the vapor retarder manufacturer's recommendations.
All other envelope building materials and finishes installed towards the cooler, exterior side of the wall shall have water vapor permeance at least ten times greater than the interior vapor retarder material."

The exceptions for this section allowed for a prescriptive approach to bypass the 10X requirement, but it would have to be broken down well for any building official to have considered it. But, given that this is old code now, it's all irrelevant....
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Old 01-29-2013, 11:45 PM   #37
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Yes, I thought it might be an older code, revised in 2007 because of the new (then) usage of exterior foamboard sheathing eliminating the (low perm) inside vapor barrier/retarder, and most of the permeability ratios (wall drying to exterior) associated with it. One still has to figure out the perm ratings of each wall, for each location- both commercial and residential -especially when not using foamboard. That’s why I needed the link from you to verify MA wasn’t under that code ruling anymore (and; that I may have missed one).
Here is a good link showing how the “I” Codes revised their definition of a vapor retarder due to BSC’s scientific research; http://www.buildingscience.com/docum...r-requirements

When using foamboard, be sure of the interior perm rating (Class); the detailed science behind it; http://www.buildingscience.com/docum...nsulation/view

So after all the drama, the advice I gave earlier meets current code but not a 4+ year-old commercial code that is no longer applicable. That’s the problem with memories, wait to you get over 60 years old, you’ll be glad if you remember why you opened the refrigerator door…. lol. I was wrong once, too. Then I double-checked --and I was wrong; that I thought I was wrong… then I typed this wrong because of wrong punkshation – and spelling... lol
Maybe tomorrow I will be correct, if I don’t get up….

Gary
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Old 01-30-2013, 09:33 AM   #38
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Old 01-30-2013, 08:07 PM   #39
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I don’t see how I am suggesting an exception to the code, MA calls for an interior Class 2 vapor barrier (asphalt paper-faced fiberglass insulation). I agreed with you and showed how paper-faced is more permeable when needed and can use it with foamboard in a heating climate (Posts 21, 23). With a Class 2, you can fill the wall cavity with whatever acceptable type you want as long as it meets the minimum R-21 requirement.

Then in Post 28; “ --- If you leave the studs at existing 3-1/2" with 2" foamboard inside against the wood boards, and add the 2" f.b. strips to the studs edge inside, fill the cavity with R-13 (3-1/2") asphalt paper-faced, your total will be R-23. Code is R-21 for your location- Zone 7; http://publicecodes.cyberregs.com/ic..._11_sec002.htm

For any that I confused (sorry), Post 21 and 23 show it is acceptable to use a vapor retarder (kraft paper) and foam in the same wall. As per code; Class 1 or 2 for location Zone 7; http://publicecodes.cyberregs.com/ic...001_par003.htm
And paper faced is a Class 2; http://publicecodes.cyberregs.com/ic...001_par005.htm

Another link showing the variable permeability of the kraft-paper; http://www.buildingscience.com/docum...uth-assemblies

Or are you talking about something else here? He is covering it with ”drywall, I hope that goes without saying.

Am I missing something, or are you? What exception to the code am I encouraging?

Gary
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Old 02-01-2013, 03:13 PM   #40
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Can't find anywhere the new code (or old the IRC even) specifically states against double vapor retarder (Class I or II) walls, but I still will never recommend doing so....Kraft on the inside (class II) and 2" XPS foam (class II) against the sheathing is not recommended by me. Do as you wish, but that's my professional opinion.
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Old 02-04-2013, 12:39 PM   #41
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Originally Posted by AGWhitehouse View Post
Can't find anywhere the new code (or old the IRC even) specifically states against double vapor retarder (Class I or II) walls, but I still will never recommend doing so....Kraft on the inside (class II) and 2" XPS foam (class II) against the sheathing is not recommended by me. Do as you wish, but that's my professional opinion.
------
Thanks for the feedback! I agree; a Class 1 (plastic, foil-faced, etc.) on the inside with thicker foamboard on the outside is very dangerous. http://www.buildingscience.com/docum...058-parthenon/

Using the "dry cup" measurement for any of the standard Class 2; kraft-paper, plywood, OSB, and 30# builders paper, can be used with foamboard. Using the "wet cup" perm rating, (because) they all allow more moisture to pass, the wetter they get- changing from a Class 2 to a Class 3. Standard framing in cold climates; builders paper, foamboard, OSB, fibrous batt insulation with paper facing, drywall. Perhaps the different permeability rating cup-- "use" is confusing, they tend to mix the two testing types in the same sentence, lol.
http://energy.gov/energysaver/articl...sion-retarders

Gary
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Old 02-04-2013, 03:06 PM   #42
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Just to stir the pot a little bit more. I just got done doing a mold abatement on a newer home built 12 years ago. Mold behind the sheetrock on all exterior walls. 3 Mil plastic vapor barrier over unfaced FG. now fast forward to today not to use plastic 3 mil as a vapor barrier just sheetrock and go over with mud tape and texture then two coats of PVA as the vapor retarder. Go figure?

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