Choosing a radiator
Cast iron, steel or aluminium?
All three heat a room well when they are sized correctly. They differ in how quickly they warm up, how long they hold their heat, their weight and how they are installed. This is a general guide: the right radiator for your room depends on the heat output you need and the space you have.
| Cast iron | Steel column | Aluminium bi-metal | |
|---|---|---|---|
| Heat-up time | Slower to warm up, because the iron and the water inside it take longer to reach temperature. | Warms up faster than cast iron. | Warms up quickly, because aluminium passes heat on readily and holds less water. |
| Heat retention | Holds its heat for longer after the heating switches off, because of its mass. | Cools more quickly than cast iron once the heating is off. | Cools more quickly than cast iron once the heating is off. |
| Weight and delivery | The heaviest of the three. Delivered on a pallet. | Lighter than cast iron. Delivered by courier up to 30kg, and on a pallet above that. | The lightest to handle. Delivered on a pallet. |
| Installation | Stands on its own feet, so the floor must carry the weight. Wall stays hold it steady against the wall, and moving it into place needs two people. | Fixed to the wall on brackets by a heating engineer. | Stands on its own feet, with the wall bracket supplied to hold it steady against the wall. Much lighter than cast iron to move into place. |
| Heating systems | Works with boilers and heat pumps. For a heat pump, size it on its ΔT30 output. | Works with boilers and heat pumps. For a heat pump, size it on its ΔT30 output. | Works with boilers and heat pumps. For a heat pump, size it on its ΔT30 output. |
| Warranty | Iron Clad 25-year manufacturer's warranty. Paint and finishes excluded. | Iron Clad 25-year manufacturer's warranty. Paint and finishes excluded. | Iron Clad 25-year manufacturer's warranty. Paint and finishes excluded. |
| Often chosen for | Period and listed properties, high ceilings, and rooms heated for long periods. | A traditional column look at a lower weight, in modern and period homes. | Rooms heated for shorter periods, upper floors, and anywhere weight matters. |
Every radiator page shows the heat output of the exact size you choose at ΔT50, the standard rating for a conventional boiler system, and at ΔT30 for lower-temperature systems such as heat pumps. At lower water temperatures every radiator gives out less heat, so size it on the ΔT30 figure if you have a heat pump. Use our BTU calculator for an estimate of the output your room needs, and ask a heating engineer to confirm it for critical installations.