Cast-iron baseboard radiators work by circulating hot water, which heats the radiator and the air around it. As the warm air rises, the system draws in the colder air that sinks to the bottom of the room.
Despite the name, cast-iron baseboard radiators do not heat primarily through radiation. Radiation begins the process, and as the warm and cool air circulate, they create currents that move the heat throughout the room. This process is called convection.
Baseboard radiators come with a thermostat, which communicates the desired heat level to the furnace. When the water reaches the correct temperature, a circulation pump moves it through the tubes. Many cast-iron radiators feature small fins to increase the surface area and radiate more heat. Depending on the age and design of the radiator system, it may be possible to control the heat of each room individually by limiting the flow of hot water to a specific section.
In comparison to newer baseboard heaters made from lighter metals, cast-iron models offer greater heat distribution. Because cast iron is thicker, it carries a higher thermal mass. Cast-iron systems generally have larger tubes, which leads to faster heat transmission and more even heat distribution. They operate silently and eliminate the pinging sounds that often come with radiant systems.