A hot water baseboard heating system uses a central boiler to heat water, distributing it to floor units throughout the home. These heaters radiate that heat out into the room, creating a convection current that moves warm air. As the water cools, it cycles back to the boiler for reheating.
Hot water baseboard heaters may also be tied into an under-floor hydronic heating system. This cycles hot water through flexible tubing under the floorboards, turning the entire floor of a room into a radiant heater.
Hydronic heating is particularly energy efficient because the hot water in a sealed system cools slowly, reducing the amount of energy needed to keep it warm. Since hot water baseboard units do not use fans to distribute heat, the system is also very quiet.