I'm finishing a room that was built between the house and detached garage. I know I need to put 5/8" drywall for fire protection after insulating the wall. Do I also need vapor barrier? If so, how do I install it around laundry hookups?

(I'm in California, so the climate is mild)

1 Answer 1


Vapor barrier goes on the warm side of the insulation (averaged year round)

If, on average, the garage is warmer than the house, vapor barrier goes on the garage side.

If, on average, it's cooler, it goes on the house side.

If you rarely close the windows, you probably don't need one at all.

Penetrations should be sealed with something like acoustic sealant (which never quite hardens, so it tends to last better than things that harden.) You can cut an extra patch of vapor barrier to aid in sealing penetrations by making a double-layer patch sealed to the main barrier.

  • So there's no code requirement specifically about between the house & garage? Someone told me about needing one to keep potential exhaust fumes from the garage out of the house. (I'm skeptical)
    – tomwhipple
    Jul 12, 2014 at 19:51

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