Foil bubble insulation under overpour

Lynne

We are laying pex on a plywood floor and pouring over it. Can we just lay down this Reflexctix bubble foil insulation and consider that our barrier as well as our insulation?

Earthfire

overpoured plywood

I use 6 mil poly for a vapour barrier and insulate between the joist under that plywood. Personally I am not comfortable with bubble wrap under on overpour giving adequate support to the floor finsh materials. Take a piece of bubble wrap and place a piece of plywood on it,jump on & do the twist . Does the plywood move around? I really don't think that any thing under a 3" thick concrete overpour has the longterm compressive strenght to not crack over bubblewrap insulation JMHO

Lynne

finish floor will be the concrete in color

So it is just plywood, bubble foil for concrete, and concrete, finished to look like tile.

heretic

foam would probably be better

1 inch of extruded polystyrene should be up to the compressive task, though it is thicker than the 'reflectix', so you may need more total clearance for the floor height.
A relative has 1-inch eps with 3 inch lightweight gypsum overpour and tile. 5 years later, no cracks.
The main advantage to this approach is that it may take less labor than the sometimes 'fussy' task of insulating under the subfloor.
There is also probably some advantage to having a complete 'thermal break' from the subfloor, but this distiction may not be truly significant with interior space below.
Best of luck.