This Floor Warming subject is of growing interest. Not just in cold climates but everywhere that Tile and stone are used as flooring.
More information is available here about the FloorHeat products in the Laticrete family.
A versatile floor warming mat for installation underneath tile and stone. Equipped with self-adhesive backing, LATICRETE Floor HEAT is simple to install and comes with a low profile wire so it is virtually undetectable beneath tile and stone floors.