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crawlspace ventilation

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  • crawlspace ventilation

    I just purchased a 25 year old townhouse in the Pocono mountains. It is built over a crawlspace, which has a gravel floor, covered with plastic sheeting. The outside (front and back) walls are insulated with spray on foam insulation. There were two vents, both in the front. They were closed over with sheet insulation, then the foam insulation was sprayed over it deliberately. So it is currently unvented.

    Is this reasonable, or should I cut through the foam and re-vent the crawlspace (at least in the summer)?

  • #2
    Re: crawlspace ventilation

    I think you will find that code requires the vents.
    "When we build let us think we build forever. Let it not be for present delight nor for present use alone. Let it be such work that our descendants will thank us for, and let us think, as we lay stone upon stone, that a time is to come when these stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, "See! This our fathers did for us."
    John Ruskin (1819 - 1900)

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    • #3
      Re: crawlspace ventilation

      Last building class I took they were planning on doing away with crawlspace ventilation with the rationale that the difference in temperature & humidity between the outside air and the crawlspace air is what causes the majority of the condensation problems.

      Claimed they weren't necessary for this purpose.

      I wonder if they help with reducing the chance of Radon exposure though?

      J.C.

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      • #4
        Re: crawlspace ventilation

        Crawlspace over a slab I could understand, but around here a crawlspace over grade with no moisture barrier as most of the older properties are and no ventilation the humidity problem would be worse I think.

        I agree that vents would help reduce Radon build-up though they may not be enough.

        2006 IMC says uninhabited spaces like crawl spaces and attics must be provided with natural ventilation openings as required by the IBC or must have mechanical supply and exhaust system.

        "When we build let us think we build forever. Let it not be for present delight nor for present use alone. Let it be such work that our descendants will thank us for, and let us think, as we lay stone upon stone, that a time is to come when these stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, "See! This our fathers did for us."
        John Ruskin (1819 - 1900)

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