There is not much more comforting that stepping into a bathroom on a winter morning to find the floor nice and warm.  Radiant heating is most common in bathroom settings because this is a place where people tend to be barefoot, and the floor tends to be a material like tile that feels very cold.   These materials are also great at absorbing heat, and make perfect flooring materials to support radiant underfloor heating.  Water underfloor heating and electric underfloor heating both warm the flooring material from below.  This heat is transferred to the surrounding air, furniture, walls, and people.  This creates both a warm floor and a warm room.  It is also a very efficient way of heating, not only for 1 room, but for an entire house.