Has anyone installed a nu heat or similar electric radiant floor heat mat under engineered hardwood flooring. Any problems with doing this. I think a warrm/heated hardwood floor would be awesome. Thinking of thinsetting the heating mat to the subfloor and then covering it with self leveling compound, then glueing the hardwood on top of the slc. Any problems with this install.

I have floated engineered woods over both mat type in floor heating and radiant floor heating and never had any issues.

No problems at all you if want them I suggest you totally go for them.