Insulation goes under the slab or else you do not get the benefit of it's thermal mass. Can't retrofit that. If you want to thermally isolate the existing slab with insulation and a new gypcrete pour, you can certainly do that for hydronic systems if you have enough ceiling height to lose the 4'' or so that it will take away. That's Expensive to do, and ony worth doing if the hydronic boiler just needs to add another zone. Adding an all new hydronic system is rarely cst effective.

If you are talking electric cables, those are a floor warming system only. They are applied to existing slabs as a comfort convenence and luxury, not as a home heating system.

Thank you for your response. I wasn't sure of the wording. But what do I do about the contractor who won't install the product according to the directions?

How was the install done? What steps were taken? Hydronic or electric? Purpose of considering radiant?

the product is Warmup foil heating for laminate. A piece of plastic was glued to the cement, then the foil heating system was laid down and the hardwood glued down to the foil. No insulation board or foam underlay, no electrician.

construction adhesive is used to glue the insulation boards to the floor. Thank you everyone for your help.

I would find the installation instructions (or get the company to send them to you via email) and then have a professional flooring inspector INSPECT (ie. you have to pay for the service) the installation. Once you have the inspection report in hand, you can then go after the installer with the "improper installation" which is then put back in their court and the installer is responsible for it.

Who hired the installer and what are the installer's qualifications? Who "sourced" the radiant heat product (did you purchase or did they?)? Radiant heat almost always requires some form of "education" as it is not a "Joe Schmoe" contractor installation. A flooring PROFESSIONAL should be able to do this and do it well.

after several conversations and comparing of her instruction manual with the one that came with the product, I finally have an understanding of what went on. The contractor bought the product, talked to "the manufacturers" and decided I was better off with what she had than the insulation boards that were recommend. I agree, an inspection is in order. Thank you for the help and instruction.

She sourced it, she ignored the recommendations and the product/install failed. Sorry to say but she is responsible for the entire thing...start to finish.

Personally I would find someone else to do the work you require. Make sure you get your money back (for parts and installation), have the original person remove the damaged product (at her cost) and start again (back to square 1...no money out of pocket and a floor ready for radiant heat install).

I would say you can get another professional at this point.