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  • foam insulation between walls

    I have a brick veneered house with a clay tile wall construction. I have been trying to find out if I can foam in between the two walls (1 to 2 inchesbetween walls). In the dead air space there is a lot of air movement. I found this out when I put in a new window. This house is very cold and was wondering if foaming this space with a low expanding foam would create more problems. House is 80 years old. I have already built a 2x4 wall on the inside with 3 1/2 inch insulation. It helped some but not what I thought it should. Would foaming this air space make a mold problem?

  • #2
    Re: foam insulation between walls

    If your talking about around the windows, yes, it will cut down on drafts in the window opening. If you talking about the entire wall I would probably say no. That air space helps get rid of excess moisture and based on the age of the house, there is probably no interior vapor barrier on the inside, so in the winter the warm moist air is driving through the interor walls and condensing in the air gap. Trap that moisture and your clay could become saturated and grow mold.

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    • #3
      Re: foam insulation between walls

      Disclaimer, I'm a plumber, not a building envelope expert.

      I understand there are different kinds of foam. Closed cell and non-closed cell. If the closed cell foam acts as a vapor barrier then the following may be true. If the cavity was filled with closed cell foam, the foam would prevent moisture from reaching the cold and condensing.

      If the house were mine I would ask the local building official his opinion. It will be informed, educated, and free.
      Time flies like an arrow.

      Fruit flies like a banana.

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      • #4
        Re: foam insulation between walls

        The R value for 1" of foam insulation ranges between 3 & 8 depending on which foam you choose. You would then have to get the price (which would be rather expensive) of drilling and installing the foam to see if it is worth it to you. http://www.oneprojectcloser.com/spra...pen-cell-foam/
        ________
        Ferrari 158 History
        Last edited by TOPDAWG; 02-24-2011, 06:40 PM.
        Mike

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        • #5
          Re: foam insulation between walls

          Originally posted by TOPDAWG View Post
          The R value for 1" of foam insulation ranges between 3 & 8 depending on which foam you choose. You would then have to get the price (which would be rather expensive) of drilling and installing the foam to see if it is worth it to you. http://www.oneprojectcloser.com/spra...pen-cell-foam/
          I'd like you to show me a foam that has an r value of 8 per inch.

          Rather than posting links to DIYer's websites, lets see something credible.

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          • #6
            Re: foam insulation between walls

            OK I do have a vapor barrier on the inside of the wall. The cost was quoted to me for $3.50 a square foot. Our county inspector I would say I have more knowledge of construction projects then they have and the only thing they inspect for is the set back from the road. My concern was with the moisture trapped in the wall. But I was worried the ( vapor) moisture would come threw the front. If it would at all do to having a double layer of insulation. (dry wall,4 mil vapor barrier, then 3 1/2 in. bat insulation, 6 in. tile bock, 1/2 to 1 1/2 foam, and then 4 in. of brick veneer). It looks like I could be making a mold problem with trapped moisture.

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            • #7
              Re: foam insulation between walls

              You only want one vapor barrier, foam is a vapor barrier and the barrier is as thick as the foam is applied.

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              • #8
                Re: foam insulation between walls

                The idea sounds good but i believe you should get some more info about the moisture before you continue. I sounds like youre trying to build the PERSIST(?) wall system I've seen where they wrap an existing building with furring strips super insulate the walls with foam and install the siding, only you siding (brick veneer) is already up. I would consult a building science professional before doing this. They would be able to figure out the moisture profile of your walls and make sure you won't have a mold or water issue down the road. Most local code officials don't know much about progressive wall structures or building science for that matter.


                Sorry for the long reply, hope it's of some use.

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                • #9
                  Re: foam insulation between walls

                  Originally posted by nehunter View Post
                  I have a brick veneered house with a clay tile wall construction. I have been trying to find out if I can foam in between the two walls (1 to 2 inchesbetween walls). In the dead air space there is a lot of air movement. I found this out when I put in a new window. This house is very cold and was wondering if foaming this space with a low expanding foam would create more problems. House is 80 years old. I have already built a 2x4 wall on the inside with 3 1/2 inch insulation. It helped some but not what I thought it should. Would foaming this air space make a mold problem?
                  Firstly, how can you be sure you get 100% coverage under the bricks?

                  Secondly, I think that even low expansion foam with crack the mortar joints. The expanding pressure may seem low but the surface area is very high.

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