Hydronic radiators are heating devices which transfer heat from the media within to surrounding room air via convection. Hot water and steam are the most common radiator media types. Radiators typically consist of a sealed hollow metal container.

In hot water radiators, hot water is pumped into the container and gives out heat. As the water cools, it sinks to the bottom of the radiator and is expelled through a pipe.

Steam flows through a radiator under its own pressure. It is easier to distribute through a heating system than hot water; however, steam is a far less efficient heating medium than hot water.

Thermostatic radiator valves allow the setting of individual radiators to meet each room’s desired comfort level. Generally the use of hydronic radiators can be more cost effective than running traditional central heating systems.

Traditional cast iron radiators have generally been supplanted by low-profile baseboard-type and decorative wall mount designs. The majority of hydronic radiators are manufactured for residential and commercial heating applications, although specialized radiators are produced for niche uses such as towel warming.