Heated mats for tile floor?

We have a basement that is split, half finished and have unfinished. The unfinished side sits directly beneath our kitchen floor, which is tile. Has anyone installed the electric heater mats under the subfloor between the floor joists, and how well did it work to warm the tile above?

Were they difficult to install as a DIY project?

The unfinished side of the basement has ductwork but isn't heated or cooled. It stays 70F or below year round.