Re: [GBlist] Re: Big Green: Radiant Floor Heating

[Sacie H Lambertson <dlambert@grasshoppernet.com>]

Not sure of the genesis of this discussion, I come down on the side of
using mineral wool under a basement slab where radiant tubes are installed.
 This is ideal in a walk-out-basement because the min wool drains and the
perforated drain tile, under the rock under the slab, can easily be taken
to day light. Because our house/basement is not yet closed in, we suffer
regular flooding in the basement when the sky opens up.  Although we have
floor drains in place, with a good rain, the cavity for the radiant heat
manifold fills with water, suggesting a lot of water under the slab.
However, given dry weather and a day, that cavity drains, which means that
the rock and the min. wool is doing its job.  I anticipate it will get bone
dry once we get closed in.
	We placed, per our designer's instructions, several inches of min wool
veritically around the entire perimeter of the slab (cutting off at the top
of the pour, a job no concrete sub will tackle), as well as 2' horizontally
in from the perimeter, this in the entire basement, both conditioned and
unconditioned.  Where we have the RFH tubes we placed 4" of the mineral
wool and given the compressiveness of the material, should have ordered a
more dense type.
	In a basement where a walk-in refrigerator or freezer is built I would
insulate all the way around the structure.  The constant 55/60 degrees of
the earth is too high for refrigeration etc.  Same principle as the reason
one would insulate under the tubes in a floor---unless of course you want
to either heat or cool the space below, isolation seems prudent.  Seems to
me that this type of space--ie unconditioned space, is automatically going
to be pretty humid, particularly in the summer.
						Sacie Lambertson
We considered the whole job of properly insulating and draining the
basement both inside and outside its perimeter sufficiently important to do
it ourselves, the best way to get it right.  No poly anywhere.

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