EPS or XPS under basement radiant slab?
JohnWalker
| Posted in General Discussion on
I believe our code requires R12 insulation under a radiant slab. Most contractors around here use 3″ EPS (beadboard) because its cheaper.
My concern is whether or not it is adversely affected by water. The poly will be water tight (code requirement) and the slab likely watered or flood cured so the insulation will get wet. Is this a huge problem for porous EPS? Persumably it will eventually dry with interior heat etc.
On a related note does poly iso have water issues?
Thanks in advance for the low down on XPS / EPS / poly iso vs. water.
John
Replies
Off the top of my head I caution using EPS. With EPS you have to check the compressive strength. They make it for under slab, but if you're just buying it at Home Depot be cautious.
XPS is more standard, but costs more. Higher compressive, R value etc.
There are some threads about it at Green Building Advisor.
I used XPS for my under slab.
P.S. - This is not my forte, I've just read other threads, articles, etc.