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Open Cell in an unvented finished attic with a ridge vent. Post New Topic | Post Reply

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Jesse Gerard
Posted: Feb 22, 2011 12:00 AM
Open Cell in an unvented finished attic with a ridge vent.

We would like any advice or opinions from the professionals on this forum in regards to installing open cell foam in our Cape Cod Style House in NJ.

We are renovating our second floor Master BR of our Cape Cod and were considering using open cell spray foam, it is basically be a finished attic space framed with 2x6 24" 0.C. with kneewalls on each side & two dormers. There are no soffits on the house but the roofer cut a ridge vent in when the roof was redone a few years back.

We are looking for any insight into the installation process of open cell foam when there are no soffits and a ridge vent at the peak, is this anything that could cause a moisture issue in the future, what about a vapor barrier before sheetrock?

FYI, the roof is black and in full sun 75% of the day.
Posted: Feb 22, 2011 09:24 AM
Just cover the vent and spray it full is all you should need. You should be OK without a vapor barrier if the officials will approve it for you. Otherwise you can put one up and it won't hurt anything. If we have closed cell in the lines we just do a couple of quick passes with it to cover the ridge vent and block it since that seals and waterproofs it. You have to be careful to not overfill it and have foam come out the top but that does a good job. You can also just put up strips of the foam board from the local big box store and spray over it too.
Jesse Gerard
Posted: Feb 22, 2011 01:49 PM
Thanks for your reply, there are no inspections on this renovation because we did not add anything to the existing structure, we just gutted the old original drywall and insulation from the 60's because it had quite a bit of water damage from the old roof leaking over time.

We have had 2 estimates from Sprayfoam Contractors in our area and both suggested similar open cell installation practices. I just wanted to come on the forums here to poke around about the procedure before going ahead with it because it is a permanent installation and we wanted to be sure the method of installation proposed was a legitimate practice because there are no inspectors looking at this job.

Thanks again!
Posted: Feb 26, 2011 08:25 PM
Closed cell is the one to use in my opinion for the roof line. It is a vapor barrier, it has a better R value then open cell (per inch)but is a little more expensive due to the smaller yield as compared to open cell.

I am interviewing contractors and I will be going with closed cell for my project.

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