SB: RE: insulating radiant floors

[jmark.vanscoter@amd.com]

I would absolutely NOT recommend you insulate the bottom of your slab. In the summer (which we have in abundance here) the floor will be far cooler than the surrounding air. In fact, I almost question the advantage or purpose of a radiantly heated floor here in Austin. Because of our climate, the earth is about a near perfect 72-75 degrees here constantly, just below the surface.

What I would recommend is very good perimeter insulation around the outside of your slab. Plus, site your house properly, make your slab very Earth-coupled, use very good detailing and windows to keep the outside out, have air-lock entries, and good roof installation and good roof insulation.

You spend the same money on those points and you will wonder why you thought about radiant heat. There are examples of this type of lo-tech technology around here already.

Mark V.S. in Austin, TX

-----Original Message-----
From: Robert T. Wyatt [mailto:rtwyatt@mail.utexas.edu]

In the northern US, I've heard that you would insulate the bottom of 
a radiant-heat concrete floor to reduce heat loss to the ground in 
winter as well as mitigate excessive condensation in the summer. 
(See first note here for reference: 
http://www.inmadcity.com/solarhemicyclo/sheet3.htm  )

I live in Austin, TX, though.  Would anyone recommend that I insulate 
my radiant concrete slab?


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