Q&A Forums
Vapor Barrier question Post New Topic | Post Reply
| Author | Comments |
|---|---|
|
Bryan Kwater
Posted: Apr 26, 2011 08:00 PM
|
Vapor Barrier question
I am obviously from Michigan and our codes require a vapor barrier of less than 1 perm in our walls and ceilings. 2" thick closed cell obviously takes care of that, but my question is about open cell. I am having a difficult time finding numbers that show that open cell foams would NOT need a separate vapor barrier. A few knowledgeable people on the forum have stated in other posts that open cell at certain thicknesses does not require a vapor barrier. Is this a state specific item, or is there a national code that deals with vapor barriers?Also, I am still looking for the <1 perm listing for open cell foams (any brand), so if anyone has documentation supporting this, I would be grateful for a link or a copy of the file. Thanks. estimator@matriccompany.com |
|
jimcoler
I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Apr 26, 2011 08:31 PM
|
Technically speaking the term "vapor barrier" has been taken out of the ICC code and replaced with vapor retarder. Now, there are class I,II, and III vapor retarders. Class I - <0.1 perms Class II - 0.1-1.0 perms Class III - 1.0-10 perms So, the old requirement is that a vapor barrier is a Class I or II vapor retarder. Some open cell foams can reach this potential of meeting this Class II VR at 8.8" thick. Some Open cell foams meet a Class III VR and that is all that is needed in zones 5 & 6. You have to check with the manufacturer of the foam and possibly calculate out the additional numbers. I know our OC foam (BioBased 501) meets a Class III VR at 3" thick. |
