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Vapor Retarder for Encapsulated Crawlspace

Joe Norm | Posted in General Questions on

Hi All,

I have begun the process of encapsulating and closing of my crawlspace to the outdoors. I am in climate zone 4C.

My question is if I plan to insulate the the 2 foot stem wall with rigid foam is there any point to bringing the plastic vapor barrier all the way up the wall also?

My plan is to bring the plastic to just below the vents, then apply the rigid foam to the whole wall.

Sound good?

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Replies

  1. Patrick OSullivan | | #1

    > My question is if I plan to insulate the the 2 foot stem wall with rigid foam is there any point to bringing the plastic vapor barrier all the way up the wall also?

    No. You just need a means of air sealing the two together so that there is a clear demarcation of 'outside' vs 'inside'.

  2. Walter Ahlgrim | | #2

    I think you will be miles ahead if you can convince yourself to say “I am going to condition my crawlspace”.

    When I hear people say encapsulate it seems to me they are looking for a free lunch they all too often seem to think all they need to do is air seal and insulate and the crawlspace will take care of its self and they are playing Russian roulette with mold and rot. You need to heat and cool the crawlspace so it is more or less the same temp and humidity as the rest of your home. When they don’t the space becomes to cool and damp mold and rot may follow if it gets and stays wet for long enough.

    Walta

  3. Joe Norm | | #3

    People in my area have successfully "encapsulated" their crawls around here without problem.

    Code says to install a fan but I have seen a few that never run and they look great. I am learning that the crawlspace thing is sooooo regional and I may live in a very forgiving area.

    Would EPS be suitable for the walls or would something less porous be better?

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