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Community and Q&A

Tar used for interior concrete sealing

banjomerkt | Posted in Green Products and Materials on

I’m in the middle of a residential new construction project, targeting Passive House requirements. It is an insulated slab on grade, double-wall stick built home, where the air barrier is on the outside/exterior wall. There is no vapor barrier, and there is an approx 20″ cavity for dense-pack cellulose. We just finished air-sealing, and my builder coated the top of the concrete slab in between the double walls (20″ of concrete) with 10 gallons of Henry’s foundation coating. Of course, this is an exterior-grade product that contains tar and a lot of nasty VOC’s. I wasn’t happy at all when I learned they had done this. My question is, is there anything I can do to help indoor air quality once the product has “cured” and is done with its initial off-gassing? My plan was to have them let it cure as long as possible before blowing in the insulation. But should I have them also top-coat it with something that would seal-in the nasty VOC’s? I’ll have an ERV always running to help with ventilation, but I don’t like the idea of having tar in my walls. Any advice would be appreciated. Eric

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  1. Dana1 | | #1

    I'm dubious that there would be any type of mop-on encapsulant that would work, but something like a heavy 2-part epoxy sealant (of the type sometimes used as retrofit vapor retarders on slabs) might cut it, but may bring it's own issues.

    Heavy aluminum foil is probably your best bet.

  2. srenia | | #2

    I would watch out for lost hair, arms, legs and maybe more,..

    You'll be fine, your builder did good. A way to stop moisture transfer from the slab to the insulation. The very fact they did this means they where thinking ahead. Is other ways of doing the same thing. Yes. Is the way they did it wrong. No.

  3. banjomerkt | | #3

    Thanks much. The builder is going to fix.

  4. nvman | | #4

    Why not cover it with 6 mil poky and seal the edges of the poly?

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