wall and overhead radiant heating systems are usually made of aluminum panels hung on the walls or ceiling. like underfloor radiant heating, these panels can be heated by either hot water or electricity. however, panels heated by hot water often leak, so electric panels are the most common. these panels can't heat as much area as an underfloor system, but they can be quickly turned on and off when a person enters or leaves the room. electric panels can reduce energy costs if panels are left turned off in empty rooms.