Electric Radiant 40 sqft Floor Heating Mat by Heatizon Systems.
This system will heat floors for new or remodel construction and can be installed under Tile and Stone, or in a mortar bed under laminate, vinyl, or carpet. Simple roll out the right sized heating mat to cover the desired square footage prior to installing the floor. At about 1/8″ thick, the heating element causes minimal floor buildup. The Heatwave Mats products offer a Limited Lifetime Warranty.
Heatizon has a calculator for figuring the square footage for the space:
Square Footage Calculator (new window)
Don’t forget to remove footage areas under toilets, counters and other areas you do not wish to heat.