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  1. #11
    Join Date
    Dec 2007

    Default Re: insulating crawl space

    The reason that dead air space is as effective as fiberglass is that the only insulation in fiberglass comes from the dead air it traps. In a bare wall cavity, air circulates up the inside sheathing (the sheetrock) and down the outside sheathing. Filling the wall cavity stops this convection of air inside the wall.

    In the attic, any heat that is conducted through the ceiling warms up the attic air and it rises out through the attic vents. You need a lot of fiberglass to slow down that convection loop. But in the floor, heat that radiates into the air below the floor, warms up that air and it rises, or is trapped against the floor, unless a breeze comes along and displaces the warm air.

    If you stop the air from being displaced by outside breezes, then the floor stays warm and heat loss through the floor is minimum. Unfortunately many codes are being heavily influenced by "environmentalists" who do not understand basic engineering or thermal dynamics. To them, the only answer is "more insulation" and most often, more insulation is not the answer.

    I tend to agree with the people you have consulted with, even with the vapor barrier down, I don't think it is going to be much of an issue and since you have already put the insulation in, I would not go take it out. Its just if you ever do this again on another house, you can use much less insulation and get the same result.
    Last edited by keith3267; 12-02-2012 at 11:57 PM.

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