Shower-Safe Radiant Heating. WarmWire floor heat cable makes it easy to incorporate radiant heat into a kitchen or bath: You simply tape cable straps to each side of the subfloor, weave the cable between the straps, and cover with a cement-based or gypsum-based mortar. The cable can be installed in spaces as small as a powder room and is approved for use in showers; a stainless steel jacket and clear urethane outer layer protect against punctures and moisture intrusion. It costs about $8 per square foot. Watts SunTouch, 888/432-8932, suntouch.com