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Old 01-20-2012, 10:52 PM   #46
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No problem. I just can't remember any information or study on sealed crawls where the poly on the walls was ever questioned as a potential problem. Personally, I don't see what issue it would cause. any moisture through the walls would still come through, but condense and run down the poly. There no organics to grow a mold...
just don't have anything official to share to 'prove' it... I'll be looking though, now that I'm curious!

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Old 01-20-2012, 11:27 PM   #47
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Poly on the walls should be fine.

Issues with closed cell foam on older brick and block homes have been noted to create spawling issues of the brick by not allowing the moisture to dry to the warm side, but I have never heard of anything as it pertains to poly.
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Old 01-21-2012, 08:44 AM   #48
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"Poly on the walls should be fine" just won't work for me. "Should be" means maybe, maybe not.

Here are two studies with pictures that show no plastic on the block walls.

http://www.energysavers.gov/your_hom.../mytopic=11480

http://www.buildingscience.com/docum...ace-insulation



Here are a few definitions from Building Science.com

Vapor Impermeable: Materials with a permeance of 0.1 perm or less (rubber membranes, polyethylene film, glass, aluminum foil). A Class I vapor control layer.


Vapor Barrier: A material that has a permeance of 0.1 perm or less. A vapor barrier is a material that is essentially vapor impermeable. A vapor barrier is a Class I vapor control layer. The test procedure for classifying vapor barriers is ASTM E-96 Test Method A—the desiccant or dry cup method.


Vapor Retarder: A vapor retarder is a material that has a permeance of 1.0 perm or less and greater than 0.1 perm. A vapor retarder is a material that is vapor semi-impermeable. A vapor retarder is a Class II vapor control layer. The test procedure for classifying vapor retarders is ASTM E-96 Test Method A—the desiccant or dry cup method.


From Advanced Energy.org

http://www.advancedenergy.org/buildi...0Southeast.pdf

"Cover the masonry perimeter walls with minimum 6-mil polyethylene vapor retarder, leaving at least 3 inches (76 mm) of exposed masonry at the top of the wall. Mechanically attach the vapor retarder material and seal it to the wall with duct mastic."



How can 6 mil polyethylene plastic be described as a vapor retarder when its actually a vapor barrier based upon its permeance?

Who is correct?

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Old 01-21-2012, 10:27 AM   #49
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Both are correct in this case.

There is a mixture of definitions out there in the market right now and the industry is moving away from the Vapor barrier designation.

All of them are vapor retarders, it is merely a case of what class of vapor retarder they are.

Poly plastic (perm rating of less than 0.1) is a Class I vapor retarder.

I appreciated your research intensive approach to this process but you will soon find out (if you haven't already) that is you look around long enough that you will find a dissenting opinion.

As most of the folks on here, many of whom have done this quite a few times, have indicated, poly going up the stem wall and foam on the walls should be fine.

Several of the Building Science papers on crawls are best case scenarios and apply to the design aspect of it. Many factors involved in retrofitting an existing crawl cannot meet the design guidelines in their best practices layout because of existing construction.

Sealed crawls, in about 95% of the cases, are the way to go. How to get there depends on the application and construction.

Poly on the floor and sealed to the stem wall is probably one of the universals followed closely by a rigid foam on the walls.

Do you have a picture of the crawl and can you summarize your construction or your concerns as a result of your construction.
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Old 01-21-2012, 04:24 PM   #50
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Thank you for the detailed reply.


I'm not promoting BSC, but I do find their information science based vs. a guess or "that's how its been done for years". Maybe time will prove BSC's data wrong.


My issue involves sealing and insulating a 3 foot high x 1,200 sf crawlspace which contains the HVAC air handler and bottom floor ducting. Along with other utilities.


I need to insulate the block foundation wall especially for Winter since the HVAC (heat pump) is struggling with the 60 degree crawlspace temperature. All other sealing measures have been finished except for the foundation walls, though I do plan to upgrade the 6 mil ground poly in the future.


The conflicting information on how to insulate the walls have the project on hold.
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Old 01-21-2012, 05:12 PM   #51
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Quote:
Originally Posted by AGWhitehouse View Post
I love how GBR deletes my post and continues on giving vague mis-leading responses. Bob Mariani posted the code for NC and it says the same as what I posted. YOU NEED BUILDING OFFICIAL APPROVAL TO LEAVE FOAM EXPOSED. No exceptions! I can't say it in any plainer english...please stop the vague information when dealing with life safety issues. It's misleading and life threating.
Your post was deleted to our staff-saved "trash bin" because it did not treat the OP with respect as per our forum rules: "Users shall treat each other with respect at all times on DIYChatroom.com. Name calling, personal attacks, or other inappropriate behavior will not be allowed and may cause your account to be banned". Found at the bottom right-hand corner of every page.
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Old 01-21-2012, 05:20 PM   #52
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Quote:
Originally Posted by Earnie View Post
Thank you for the detailed reply.


I'm not promoting BSC, but I do find their information science based vs. a guess or "that's how its been done for years". Maybe time will prove BSC's data wrong.


My issue involves sealing and insulating a 3 foot high x 1,200 sf crawlspace which contains the HVAC air handler and bottom floor ducting. Along with other utilities.


I need to insulate the block foundation wall especially for Winter since the HVAC (heat pump) is struggling with the 60 degree crawlspace temperature. All other sealing measures have been finished except for the foundation walls, though I do plan to upgrade the 6 mil ground poly in the future.


The conflicting information on how to insulate the walls have the project on hold.
There is not a whole bunch of conflicting information.

Rigid foam is great and works quite well.

You should call you code enforcement officials and check to see what requirements are necessitated for whatever foam you go with.

You can quite easily use foam and cover it with a JM spider insulation or rockwool batts if need be.
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Old 01-23-2012, 12:59 PM   #53
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Quote:
Originally Posted by Bob Mariani View Post
The most commonly used rigid foam board used on crawlsapce walls is probably Thermax Sheathing and it has passed FM 4880 which means it does not require ignition barrier protection. You can look it up by going to dowbuildingsolutions.com


And almost all professional spray foam does not need an ignition barrier. Where do you get this info? I do this for a living! And I pass inspections every day in many many towns both in CT and NY
Please show me the code section that allows for foam to be left exposed without building official involvement. That is the issue here. It needs to be made clear that you can leave CERTAIN assemblies exposed, but they MUST HAVE PRIOR APPROVAL. I've posted the code governing the design side in CT and it does not allow it to be left exposed without building official approval. The contractor side has always assumed their own way of things, hence the reasons for all the WTF moments when buildings get inspected by true professionals....
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Old 01-23-2012, 01:32 PM   #54
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AGW,

From your experience and educational background, do you advocate installing polyethylene film (6 mil plastic) from ground level all the up (in my case to within 3 inches of the rim joist) block crawlspace walls?

Also, if insulating a block crawlspace wall, would you specify extruded polystyrene (XPS) rigid foam board or foil faced polyisocyanurate foam board?

I understand local code is the final word but just interested in your point of view.
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Old 01-23-2012, 03:08 PM   #55
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Code states the foam must have an ignition barrier. Almost all commercial closed cell foam now meets this requirement. I do this work every day and jobs are passed every time. I already stated the manufacturer's reference to this fact... fortunately building inspectors here get BPI certified so they are a up to the new products and specifications of those products.
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Old 01-23-2012, 03:19 PM   #56
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Bob,

Would you mind placing a link to a fire rated foam board that is code compliant? Or can you get me the manufacturer's name and specific product name?
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Old 01-23-2012, 03:52 PM   #57
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I just called Dow. Here is what was emailed to me:

http://building.dow.com/ee/pdf/ESR-2142.pdf

Section 4.2.2 specifies the types of foam board, X and IV, that can be installed without a thermal or ignition barrier.

Table 1 lists specific product names by their type (X, IV, etc).

ILocal building department may want to see this document.

I suspect there is some hidden catch which prevents leaving the foam uncovered.

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Old 01-23-2012, 05:31 PM   #58
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Er, that would be in the link I gave you in my post #22, linking to Dow and that ER in my #22 (there also)--- the last one listed....

"I suspect there is some hidden catch which prevents leaving the foam uncovered. " ---- yes, you have to meet their conditions of use and present it to the building official before you start as I said earlier.

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Old 01-23-2012, 05:56 PM   #59
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The plastic alone is fine on the walls unless it is a conditioned crawlspace. You want conditioned if the HVAC ducts are down there. To condition---- insulate the walls, otherwise, insulate the floor. I would mastic or asphalt emulsion the plastic as it has to be air tight. You will still have problems with the joists getting wet from any other moisture source under there, along with radiation because the walls are not insulated, only plastic covered, leaving a cold crawlspace: http://www.buildingscience.com/docum...n-crawlspaces/

http://www.buildingscience.com/docum...bout-diffusion

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Old 01-23-2012, 07:42 PM   #60
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Quote:
Originally Posted by GBR in WA View Post
Er, that would be in the link I gave you in my post #22, linking to Dow and that ER in my #22 (there also)--- the last one listed....


Gary

Yes, I see that now. I did look through the earlier replies but overlooked the link to the other post's link.

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