I installed Thermosoft electric radient heat into a converted back patio addition last year. I used an insulating cork subfloor tratment, topped with the heating mat, then covered with leveler, before installing ceramic tile. The heating elements work GREAT and I can usually go with no other supplimental heat in the 150 SF addition. I am really glad I spent the $ to do this in my addition and would do it again in a heartbeat.