Types of radiators: which one suits your room and system?

The main types at a glance

Every wet radiator does the same job: hot water from the boiler flows through it and heats the room. What changes is the shape, the material and how much surface it packs into a given space.

Panel radiators and what type 11, 21 and 22 mean

Steel panel radiators are what most British homes have. They are named by the number of panels and convector fins. A type 11 is a single panel with a single set of fins, a type 21 is two panels with one set of fins and a type 22 is two panels with two sets of fins. Some ranges also include a type 33 with three panels.

The more panels and fins, the more heat from the same height and length, and the deeper the radiator sits off the wall. That is why a double convector is often the answer when a room needs more heat but the wall space under the window cannot get any bigger. Compact panels have covers on top and at the sides; flat-fronted panels look cleaner but cost more for the same output.

Column and cast iron radiators

Column radiators are made of vertical tubes, usually two to four columns deep. Steel column radiators give a traditional look at a fraction of the weight of cast iron and suit both period and modern rooms.

Cast iron radiators are heavy, slow to warm up and slow to cool down. That thermal mass is pleasant in a high-ceilinged Victorian room, but it also means they need strong walls or floor-standing feet, and they respond slowly to a thermostat. If you are keeping originals, our guide to replacing a cast-iron radiator covers weight, connections and valves.

Aluminium radiators

Aluminium conducts heat well and aluminium radiators hold little water, so they warm up quickly and are light enough to hang on plasterboard with the right fixings. They suit rooms that are used in short bursts, such as a home office or spare room.

They are usually more expensive than steel panels for the same output, and aluminium needs the right inhibitor in the system to protect it from corrosion. Check the manufacturer's requirements before mixing aluminium radiators with an older steel and copper system.

Vertical and designer radiators

Vertical radiators free up wall space under windows and suit narrow walls in hallways and kitchens. Designer radiators come in almost any shape and finish. The catch is output: many are single panels or slim tubes, so a radiator that looks big on the wall may give out less heat than a modest double panel. Our vertical vs horizontal radiators guide explains why you should compare watts rather than size.

Towel rails, electric and dual fuel radiators

Heated towel rails dry towels well but usually give out less heat than a panel radiator of the same size, so a larger bathroom may need a radiator as well. A central heating towel rail only works when the heating is on; an electric or dual fuel rail can run in summer too. Our towel rail central heating or electric guide covers the choice.

Standalone electric radiators need no pipework and can suit a room that is hard to reach from the heating system, such as a loft room or garden office. They cost more to run than radiators heated by a gas boiler, so they are best kept for rooms used occasionally.

How to choose the right type

Style comes last. Work through these points first, and the choice of type usually narrows itself down.

• Heat output: work out what the room needs in watts and compare radiators at the same ΔT rating
• Wall space: horizontal panels for under windows, vertical or column for narrow walls
• Wall strength: cast iron and large column radiators may need floor feet or a solid wall
• Pipe positions: new radiators with different pipe centres may need pipework altered
• Heating system: at the lower flow temperatures used by heat pumps, radiators give out less than their rated output, so larger panels are often needed
• Room use: fast-responding aluminium for rooms used briefly, cast iron for steady background heat

Replacing or upgrading radiators

Swapping a radiator for one of a similar size and pipe centres is quick. Changing the type, moving it to another wall or adding one is more involved, because the pipework and valves may need altering and the system has to be drained and refilled. Our guides to choosing radiator size and output, moving or adding a radiator and radiator valve types compared cover the details, and how long do radiators last explains when replacement makes sense.

Loyal Plumbers repairs and replaces radiators across London and inside the M25 with 10 vans. Call 020 4652 8585 or send an enquiry with the room sizes, the radiators you have now and the type you are considering. We will check the output, the pipework and the system, and tell you what will actually heat the room before you buy.