[GBlist] re: radiant floor heating

[Chris Koehn <chris@koehn.com>]

FWIW: I put 2" of rigid Dow board under our radiant heated slab (in a
walk-out basement) with 6 mil poly on top of that. For one thing, the poly
is required by our code. For another, I think it's a reasonable way to
minimize radon intrusion (we do have high pockets or radon in our State).
And for a third, it is an efficient vapor barrier, which, if executed
properly, does not adversely effect the curing of the concrete. It is of
course important to be sure the concrete doesn't dry too rapidly from the
top down; this can be achieved by keeping the slab lightly misted, or
covered with wet tarps or burlap in hot dry conditions. Dow board, by
itself, is not meant to achieve the functions of vapor barrier and radon
barrier. While we did over dig our basement hole 10" and poured on 10" of
washed stone (the Superior Wall foundation is also set on 10" of stone, thus
creating one big French drain..) IMHO this doesn't go far enough toward
remediating radon and vapor.

Keeping dry, and warm,

Chris


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