I had open cell foam sprayed on the inside of my 30x40 pole barn. I will be installing 2x4 girts across the front of the poles and then attaching OSB to the girts. I should install a vapor barrier since open cell does not act as vapor barrier, correct? Can I staple the plastic to the girts or must I staple it to the posts before installing the girts? Thanks for your help.
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Do I need a vapor barrier?
- Thread starter 86Vette
- Start date
rburke65
Well-known member
Well you’d probably get better support from stapling it ti the girls. If the foam doesn’t give you a vapor barrier....then I think you would need one.
JoeMcGov
Well-known member
Will the pole barn be heated? Cooled? Both?
BothWill the pole barn be heated? Cooled? Both?
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theoldwizard1
Well-known member
OPEN CELL FOAM ! You know have a giant sponge that will stay damp for weeks after high humidity.
Chris705
Well-known member
What did your spray foam installer say about the need for a VB? In your climate zone a VBis likely not needed at all. Unless you will have excessive amounts of moisture in your garage all reason points to not needing a VB. Current ICC building code does not require a VB in your zone when using either closed or open cell foam insulation. Look at perm ratings for both open and closed and I think you will see you shouldn’t be concerned, especially when compared to other types of insulation.
machsnell
Well-known member
Green Building advisor article that specifically addresses your concern.
Article says no but read comments below, they are a little heated and all over the place so who knows?
I do have 5.5" of open cell. I am sure i will need to cut a hole open in the next 5 years and if i remember (unlikely) i will find this and post my findings. I am sure hoping its a no because i didnt install a vapor barrier.
https://www.greenbuildingadvisor.com/article/open-cell-foam-beats-closed-cell-foam
Article says no but read comments below, they are a little heated and all over the place so who knows?
I do have 5.5" of open cell. I am sure i will need to cut a hole open in the next 5 years and if i remember (unlikely) i will find this and post my findings. I am sure hoping its a no because i didnt install a vapor barrier.
https://www.greenbuildingadvisor.com/article/open-cell-foam-beats-closed-cell-foam
Chris705
Well-known member
I also researched prior to installing open cell in lieu of closed....was educated into understanding how perm ratings work and how close closed and open are in terms of perm rating....further knowing I would not have a ton of vapor produced in my garage, I went with full depth open cell in walls and roof. Initially I was going to hang a VB but decided against it after reading several on-line articles similar to this one. Also helped that the installer told me he would do either open or closed but if it was his place/house he would use the open with no regrets.
This article is not from my installer but we are in the same climate zone.....
https://energsmart.com/wp-content/uploads/2017/08/Open-v-Closed.pdf
This article is not from my installer but we are in the same climate zone.....
https://energsmart.com/wp-content/uploads/2017/08/Open-v-Closed.pdf
DC73
Well-known member
Whether or not you need a vapor barrier, a vapor retarder, or nothing is highly dependent on your specific climate. If you do install a vapor barrier and there is some type of material on the other side of the foam that also acts as a vapor barrier or retarder, if the foam gets wet, it will likely never dry out and could cause you problems. In the absence of a definitive solution from a local engineer with considerable experience, go with what you learn from the GreenBuildingAdvisor site.
DC
DC