I am insulating my detached garage. I was wondering what the purpose of the paper attached to the shiplap sheathing is. It has lots of areas that are ripped. I am not sure if I should rip it out or just leave it behind the insulation. Could somebody give me an explanation for this?


Is your climate primarily hot, or primarily cold? If hot, repair it. If cold, rip it out. The vapor barrier goes on the (on average over the year) warm side of the insulation. So if you are insulating to heat, but won't be cooling - inside. If you will be cooling more than heating, outside.


It is your vapor barrier I would patch it where you can.

  • Yes, Ed is correct. The old way they did vapor barriers was with tar impregnated paper otherwise known as roofing felt. 15# felt comes in rolls 36" by 144', and 30# felt is twice as thick and is only 72'. Repairing it if possible is the best solution. – Dotes Nov 1 '17 at 21:04
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    Thank you both for the answer! I really appreciate it! I live in Southern Michigan where it gets cold during the winter and hot during the summer but I only plan on heating the garage. The answer by Ecnerwal says the vapor barrier goes on the warm side of the insulation so I think I am going to rip this old one out and put a new vapor barrier between the insulation and the drywall so it will go Vinyl siding->Shiplap->Studs/Insulation->Vapor Barrier->Drywall. Sound correct? – Cameron Henige Nov 3 '17 at 1:30

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