Types of Central Heating Radiators Explained

Which is Best Type of Radiator for Your Home?

When it comes to keeping your home warm, the boiler gets all the glory, but your radiators do the actual heavy lifting. If you are upgrading your heating system or renovating a room, you might be surprised by how many different types of central heating radiators are on the market today.

Choosing the right one isn’t just about aesthetics; it’s about heat conductivity, durability, and system efficiency. From traditional steel panels to modern designer units, here is the iWarm.co.uk guide to the different types of central heating radiators.

Standard Steel Panel Radiators (Type 21, Type 22)

These are the white, corrugated radiators you see in the vast majority of UK homes. They are made of mild steel, which makes them tough, reliable, and highly cost-effective. You will often see them categorized by “Types”:

• Type 11 (Single Panel): One radiator panel and one set of internal convector fins. Slimline, but lower heat output. Good for hallways or small bathrooms.
• Type 21 (Double Panel Plus): Two panels but only one set of convector fins sandwiched in the middle. A great balance of slim design and good heat output.
• Type 22 (Double Panel, Double Convector): Two panels and two sets of fins. These are thicker and stick out from the wall more, but they pump out a massive amount of heat, making them perfect for large living rooms.

Aluminium Radiators

Aluminium is a highly conductive metal, meaning these radiators heat up incredibly fast and cool down just as quickly.

• The Pros: Because of their superior conductivity, an aluminium radiator can be physically much smaller than a steel or cast iron radiator while putting out the exact same amount of heat. They are lightweight and put less strain on your walls.
• The Cons: Aluminium is softer and less rugged than steel or iron. It is also highly susceptible to internal corrosion if your central heating water isn’t properly treated (more on that below).

Cast Iron Radiators

Heavy, imposing, and incredibly durable, cast iron radiators are the traditional choice, often seen in period properties and older homes.

• The Pros: Cast iron takes a long time to heat up, but once it gets hot, it stays hot for a very long time, gently radiating heat into the room long after the boiler has switched off. The material is also exceptionally tough and long-lasting.
• The Cons: They are incredibly heavy, requiring sturdy floors and strong walls. Because they take a long time to reach temperature, they aren’t as responsive if you want to heat a cold room in a hurry.

Designer Radiators (And the “Baffle” Warning)

Designer radiators, particularly tall vertical ones, have become hugely popular for their sleek, modern looks. While high-quality designer radiators are fantastic, there is a hidden danger in buying cheap, unbranded ones online.

Inside a good radiator, there are baffles, which act as internal diverters forcing hot water to travel up and circulate through the entire radiator before exiting. Many cheap designer radiators lack these baffles. Without them, the hot water takes the path of least resistance, shooting straight across the bottom from the inlet valve to the outlet valve. The result? The bottom of the radiator is boiling hot, the top stays freezing cold, and your room never warms up. Always buy from reputable heating brands.

The Golden Rule: Central Heating Inhibitor

Whether you choose tough cast iron, standard steel, or highly conductive aluminium, there is one absolute necessity: Corrosion Inhibitor.

A central heating system contains a mix of metals – copper pipes, a brass pump, a stainless steel boiler heat exchanger, and steel or aluminium radiators. When water flows over these mixed metals, a chemical reaction occurs that causes internal rust and a thick black sludge (magnetite). This sludge blocks pipes, ruins boilers, and creates cold spots on your radiators.

Aluminium radiators are particularly vulnerable to this environment. To prevent it, your heating engineer must add a specialist chemical central heating inhibitor to the system water to protect the metals and keep everything running efficiently.

Need help choosing or installing the right radiators?

Getting the right heat output (BTU) for your room size is crucial. At iWarm.co.uk, we can calculate exactly what you need and ensure your system is properly protected.

Contact us to discuss your heating upgrade.