Insulating a concrete slab for PEX heating?

[Crazy Legs]

I started another thread about building my future 24x36' garage on fly ash but i figured this is a different topic. once i get that problem figured out, this will be a concrete slab w/ PEX heating in it and my question is do i add the 2" pink insulation under my concrete slab or can that even be done? or put it on the outside of the slab? for some reason i've gone stupid and can't get this through my head lol.
We just did my dad's shop and we put that under his floor but it had an 18" wall around it all. Thanks

 

[Swammy]

I just finished my pad

We used 6mil poly, then 2" insulation ( ours was green ), then the mesh, then the pex - 9 circuits , ( took 7 hours ) 40' X 65'

then 5 -6" of concrete.( We poured 2,600' ) . Took 1 day to pour and finish

Let me know if you have any other questions

Dave

 

[Krodad]

Yep, right under the slab. I always suggest using a 25psi foam rather than the 15psi which is what most of the big boxes sell. If you go to a concrete construction supply distributor, they can set you up with the 25psi stuff.

If I remember correctly, you are from Osky...call up Carroll Distributing down in Ottumwa and ask for Steve Chmelar...he'll set you up and he's one of the smartest guys around when it comes to concrete construction. Anything else you could possibly need can be handled by them as well.

 

[Crazy Legs]

yep your right i'm in Osky, thanks for the help guys!

This maybe a stupid question but if understand this correctly, you just have the vertical board (forms) and put the vapor barrier & 2" insulation ****'ed up against the board, so when its all poured & forms are removed it'll look like exposed 2" of insulation then the 5+" on top? (AKA, you'll still be able to see the insulation?) Over time that insulation won't calapse and then the slab is just floating on a hope and a dream of sliding off my fill? or am i just being stupid and i shouldn't worry about it lol.......... Thanks again guys!

 

[W-Cummins]

I assume that your going to have either a foundation around the outside or at least a thickened edge around the slab to support the walls (ie. slab 4" and edge 12"X12"). So you will not be able to see the insulation from the outside.


William...

 

[Crazy Legs]

yeah i was thinking about a single row of concrete blocks around the perimeter & i forgot about making the edges thicker so yeah i feel dumb now lol Thanks for your help!!!

 

[BowtieNut]

For my garage, I put the 25psi 2" foam under the entire 4" slab, and under the 12" x 12" thicker edge. Then, after the blocks were done I finished "wrapping" the 2" foam up the side to the top edge of the blocks, so yes, mine was still visible. I finished it by wrapping the exposed foam with aluminum the same color as the soffit/fascia, and up a few inches under the bottom of the siding. Then I backfilled so that the bottom of the aluminum is 6" or so below grade. Seems like it worked pretty good, and looks real good too. Now the only part of my garage that's NOT insulated is the slab for 3" or so in front of each garage door.