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Wood floor insulation failure

Tommy Alexander | Posted in General Questions on

I live in a 1960’s home that I’m currently doing a major remodel on. The house is built on a convential foundation with a vented crawlspace. The floor joist are 2×8’s on 16 inch centers. The subfloor is 1×6 pine, with 3/4 inch particle board over the pine. In the bedrooms the  particle board was covered with linoleum.  Another layer of peel and stick linoleum was added over that through the years. Then plush carpet with pad over the peel and stick. I put unfaced r30 fiberglass insulation between the floor joists, completely filled, and 1 inch owens corning pink fomular foam board nailed to the bottom of the floor joist. During this remodeling I have been underneath my floor in the crawlspace and found the two bedrooms sealed with the foam board covered with drops of beads of water on the bottom side. Enough of sweating that the plastic on the ground was covered in puddles of water. I removed the foam board and found the insulation damp, and termite damage on several floor joist. So I removed all of the foam board and insulation, and replaced the damaged floor joist. I am sealing the rim joist and concrete block foundation on the exterior.  I live in Zone 3. Any ideas on why I had the moisture problems? I plan on using Prosoco liquid flash on the exterior of the concrete blocks, and 2 inch fomular on the outside of that. Any advice would be helpful.

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  1. Steve Knapp CZ 3A Georgia | | #1


    Is the foam taped and caulked? Where are your ducts located?

    How far along are you with air sealing your crawlspace?

  2. Tommy Alexander | | #2

    No, The foam was not taped and caulked. My ducts are in the attic. I haven't started the air sealing of the crawlspace yet. I have removed the brick off of the exterior walls and blocks, and I'm down to the wall studs, rimjoist, and blocks.

  3. Tommy Alexander | | #3

    I only had the foam board covering the bottom of the floor joist on two of my bedrooms. I removed all of the foam board and the fiberglass insulation, to repair my rotted floor joist.

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