Yes, thats correct, but when I get the job date I'll have about 24hrs. to empty the room and only then check in the center.

Before the actual job starts I will be digging out the little corner I mentioned earlier or drilling down from there but even if I see some insulation, there's no guarantee that it won't be just around the perimeter.

That's why i had decided to go with an insulated overpour ( albeit with less thermal mass ) than thicker slab and risk not having insulation below.

Do I have another alternative?

Definitely do NOT use polyiso under a slab. Use Type-II EPS (1.5 lbs/cf density) if you will tie your PEX to mesh or rebar. Use Type-IX EPS ( 2 lbs/cf density) if you will staple your PEX to the EPS. You could use XPS too, but it’s more expensive, it isn’t green and after a couple decades it degrades to same R-value performance as EPS.

Yes, if you do NOT already have an existing vapor barrier under the existing slab, you should include a vapor barrier in this phase. If you are going to finish the floor in someway other than a concrete finish, you should put the vapor barrier on top of the insulation. This will prevent water from the pour getting between the old slab and the new insulation which will then result in moisture retention for a long time which can potentially cause problems with any other floor finish.

Again, if your floor is exposed to outdoor conditions in Montreal, you really should have something like 2-4" of EPS insulation under the floor and along the floor perimeter sides. And I have never heard anyone complain about having too much insulation under a HR floor either. A HR floor is typically 5-20F higher in temperature than the indoor temperature, depending on how well insulated and sealed the building is. So you will have an enormous floor heat loss and a very inefficient heating system if you don't properly address this. Another alternative would be to not do HR heated floors, but instead do HR heated wall panels possibly supplemented with mini splits.

HI all, I was contacted by the cement contractor who's back from vacation and he mentioned to me his preference of having the wire mesh elevated in the over-pour and not sitting at the bottom. This makes sense to me to strengthen the slab but as I really can't see myself fixing the pex to the mesh and flipping it over ( I'm sure I'll mess it up ) , I'm curious if any of you would recommend I staple the pex to the insulation at the bottom then fix the mesh on top or maybe fix the pex to a bottom layer of mesh and lay another on top.

The flip is easy....Two people no problem.....good luck with what ever you decide.

I did the whole basement of a 3700 sqft ranch this way.