Ask Experts Questions for FREE Help !
Ask
    cannon256's Avatar
    cannon256 Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Oct 1, 2011, 02:54 AM
    Vapor barrier under and existing steel roof
    I have a steel roof attached to 2 x 4 perlins attached to 2 x 10 roof rafters (cathedral ceiling). You can see the underside of the steel roof from inside the room. My question is should I install R-38 faced insulation between the rafters faced side towards the room and not concern myself with any additional vapor barrier against the underside of the steel roof. It's a camp I'm renovating in the Northeast.

    Mike
    joypulv's Avatar
    joypulv Posts: 21,591, Reputation: 2941
    current pert
    		  
    #2

    Oct 1, 2011, 03:11 AM
    Right, a vapor barrier protects the rafters and purlins (or any wood past the insulation).
    I think you should still have air channels leading to vents no matter what kind of roof you have, to allow for some cooling of all the wood that will now be cooking away in the summer heat, and to allow any little moisture that does get through a way to escape.
    I don't recall seeing vents (ridge or otherwise) on metal roofs around New England, but maybe they all have gable windows or gable vents, or I just missed seeing any of they other types.
    hkstroud's Avatar
    hkstroud Posts: 11,929, Reputation: 899
    Home Improvement & Construction Expert
    		  
    #3

    Oct 1, 2011, 05:01 AM
    Yes, always install the insulation with the vapor barrier to the warm side. Never install more than one vapor barrier.
    SpringtimeHomes's Avatar
    SpringtimeHomes Posts: 78, Reputation: 12
    Junior Member
    		  
    #4

    Oct 2, 2011, 10:08 AM
    My main question would be why are you insulating? If it's a Summer camp only, in New England, I don't see the point. Is it too hot in the summer? Are you converting it for Winter use? Above advice is correct for VB, however, don't expect a big temperature difference because the cavity insulation strategy is not nearly as effective as it could be. I would explore using rigid foam below the rafters.

    Building Science Corp roof venting details
Not your question? Ask your question View similar questions
 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Vapor barrier in Bathroom [ 7 Answers ]

I am doing a bathroom remodel in my Central PA home. I have heard several different opinions on how to install a vapor barrier. I was told by one person that I should install unfaced insulation on all exterior walls and then install a 4 mil poly vapor barrier. After that, I should install green...

Vapor barrier in ceiling? [ 2 Answers ]

My Kitchen has an old panel typed ceiling which I really dislike and is starting to show unevenness due to the old glue coming undone. Plan is to just rip it down and replace it with drywall. However I have a question about installing a vapor barrier.. Right now it is just ceiling titles, then...

Vapor barrier behind greenboard. [ 2 Answers ]

Hello: In doing greenboard sheetrock in a bathroom, I have been told that I should not use a vapor barrier over the insulation for outside walls. If this is correct then why? In addition is any problem expected if regular drywall screws are used instead of stainless Screws? What...

Double vapor barrier [ 1 Answers ]

Will there be a potential problem using a DOUBLE vapor barrier as in the following setup? Bedrooms were cold/drafty. Removed the drywall on the outer walls, sealed all leaks and put in new insulation. The insulation has the paper vapor barrier attached, installed toward the heated room. As...

Vapor barrier needed? [ 2 Answers ]

Installed 9" of spray foam insulation (Sealection 800) in roof system (R=38) in a home in Massachusetts. Bldg Inspector says we need a vapor barrier, but manufacturer says no barrier is needed with this product. Anybody have any knowledge in this area? Does open cell/closed cell make a...

View more questions Search