PEX without insulation?

[nvbigblue]

{EDIT} Ooops... this probably should have been under Heating & A/C, and I see some else posted almost the same question there, so my search foo must be weak today. hehe.. MODS, please move as needed.

Hey guys,
I searched around but didn't find anything...

So my county has gotten on an engineering kick as of late..... when I discussed my building plans with them, they insisted that the concrete layout be signed off by an engineer. No problem, they came with my building , however, as soon as I mentioned the possibility of adding insulation and PEX for in-floor heating, they said this would require a new set of plans, since none of this is on my current plans. Even after explaining to them that PEX is basically the same as a water pipe or power conduit in concrete, and the dirt work would be changed to keep the slab thickness the same, so nothing on grade would be changing, they stuck with with that decision. It appears their main concern is that the plans call for a solid slab, not a slab separated from the footings by the insulation. The fact that the rebar is tied into the footings didn't seem to matter.
I don't know if I would ever use the in-floor tubing, but of course, it a little easier to install it during the pour. So one of my neighbors suggested just laying (tying) the PEX down on top of the rebar prior to the pour, but after the dirt work inspection . So the question is, is it worth the effort to do this without any insulation below the slab and along the footings? Or would I just be dumping heat ($$) needlessly into the ground?
The building won't be going up until early next year, so all of this may change by then....
I did not have a chance to actually speak to one of the inspectors...this was the office staff.
Thanks for the input!

NV

 

[KRB52]

Any heat generated is going to go from a place of more heat to a place of less heat, until things have equalized. There is a good chance that you will be wasting heat to the ground without insulation. Maybe go back to the building inspectors office and talk to one of the inspectors, get his/her "official" opinion. Then try to have that same inspector come out to do the inspection(s).

 

[Rookie2]

no don't guess ! the heated slab has to be separate and insulated from the wall footers and underneath otherwise you loose so much heat you'll shoot yourself ! the heat will go down 6 feet before it stabilizes. depending on sq.ft. the finishers will trample and kink the pex ,i wire tied mine to 6"x6" wire mesh making it easer to install and walk on.

get a reliable heating contractor to lay it out and quote it so you have a better idea of what your getting into. its not cheap.

 

[Architorture]

If you intend to always keep the heat on at a constant temp it makes sense not to use insulation I order to create a large heat sink below...but if you plan to turn the heat on and off frequently then you want the insulation otherwise it takes forever to get up to temperature

 

[Sureshot]

Being in Nevada I would weigh the cost. I don't have insulation under my floor and many don't around here. The ground is not a heat conductor like steel but you will have some losses. I might guess spending the money on a solar collector would make more sense. If the heat is free who cares if you lose some.

This combined with the above post. The heat sink takes a long time to cool even here so your climate seems like a cakewalk but it is also what you are acclimated to