Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Alan

you want it on top of the foam. Just like your walls, the moisture barrier
goes on the warm side of the insulation

"arw01" wrote in message
ups.com...
Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Alan

"arw01" wrote in message
ups.com...
Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.


It is always easier to understand and answer questions when they are posted
in real english. Cryptic attempts to express bits and pieces lend
themselves to misunderstanding and assumption. It's not that hard to form
complete sentences that communicate.

Given a conflict between a concrete engineer and a radiant installer, I'd go
with the one who knows the product - the radiant installer.

--

-Mike-

arw01 wrote:
Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Alan

I'm not sure what the correct answer is. Under the insulation I
suppose there is a risk of getting holes in the barrier. Above the
insulation and you now allow moisture up around the insulation closer
to the floor. I do know this though.... I have radiant floor heat in
my basement and you are going to LOVE it!!!! My wife and I were in
Atlanta when the floor was done so I'm not sure where the plastic is or
even if there is any at all. (monkey boy contractor, as my wife likes
to call him) We've never had any moisture problems.

Bryan

DamnYankee wrote:
arw01 wrote:
Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement



we put the moisture barrier under the foam for two reasons. first, we staple the heat tubing to the foam, and you'd have to punch the poly full of holes. more importantly, you would tear the hell out of it during the pour.

the moisture barrier under a slab does not function the same as a
moisture barrier on a wall. the under slab barrier's role is to block
moisture movement by capillary action from the ground into the
concrete. a vapor barrier on a wall is blocking moisture from moving
from inside the heated space into the insulated wall cavity.

i believe the IRC was recently changed to allow NO vapor barrier if
foam is used under the slab (since the foam blocks capillary action
anyway).

Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Alan


Well now, all these posts really cleared things up, eh Allan?!!

Gotta go with the guy doing the heating install, his product.

arw01 said:

Radiant heat shop floor:

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Opinions are like assholes, so here is mine:

The barrier does not perform the same purpose as the Kraft paper on
insulation, it exists to prevent water migrating into the slab from
the ground rather than preventing humidity from the heated space from
condensing in the insulation. But you DO want a barrier! Can't
decide where? If it bothers you, how about in both locations. I can
guarantee you it will get punctured here and there during the install
of the tubing and during the pour anyway. Redundancy couldn't hurt.

Also, a layer of lawyers under your pour is good luck... for everyone.

FWIW

On 30 Sep 2006 04:42:38 -0700, "arw01"
wrote:

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

Go with the method that conforms to the warranty on the system.

Mike O.

On 30 Sep 2006 04:42:38 -0700, "arw01"
wrote:

Radiant heat shop floor:

Top soil has been removed
very hard base ground (use a breaking bar to be able to dig in it)
3-7" of 3/4" crush gravel

moisture barrier HERE?

2" polystyryene extruded foam insulation

moisture barrier HERE?

concrete reinforcement mesh
1/2" pex heat tubing
4" concrete with plasticizers and fiber reinforcement

Everyone in the businss has a different opinion if it's below the foam
or on the foam.

Concrete engineer says on the foam
radiant installer says below the foam.

I'm not a concrete guy, but I've always seen it below the foam when
others are doing it- when it's used at all, that is. They don't do it
everywhere. Makes more sense to me to have it below the foam- it's
bound to help the foam hold up longer when it's isolated from the
dirt.

On 30 Sep 2006 05:42:20 -0700, "marson" wrote:

the moisture barrier under a slab does not function the same as a
moisture barrier on a wall. the under slab barrier's role is to block
moisture movement by capillary action from the ground into the
concrete. a vapor barrier on a wall is blocking moisture from moving
from inside the heated space into the insulated wall cavity.

I talked with a plumber about that a couple of months ago (making
converation at a job site) and his contention was that the vapor
barrier was to help prevent Radon emissions and had little to do with
moisture, but as another poster pointed out, opinions are like
assholes.

i believe the IRC was recently changed to allow NO vapor barrier if
foam is used under the slab (since the foam blocks capillary action
anyway).

Depends on the county inspector- some places, they don't care and
won't enforce it, other places they do. But as I understand it, it's
still in the code.