Types of radiator explained: panel, column, vertical and more

Updated 6 November 2026 · By the Radiator Installation team

Short answer: Most UK homes use steel panel radiators, sold as Type 11 (single panel, single convector), Type 21 (double panel, single convector) and Type 22 (double panel, double convector), with each step giving more heat from the same wall space. Column, vertical, aluminium and cast iron radiators suit different rooms and styles, but always compare their rated output, not their size.

Panel radiator types

Steel panel radiators are described by a two-digit type number: the first digit is the number of water-filled panels, the second is the number of convector fin sets welded behind them. More panels and fins mean more heat from the same height and length, but a deeper radiator.

As a rough rule, moving from a Type 11 to a Type 22 of the same height and length gives somewhere around 60 to 80 percent more heat, which is why swapping an old single panel for a double convector is such a common fix for a cold room. The extra depth matters behind doors, in narrow halls and where curtains or furniture sit close to the wall, so measure the clearance before choosing.

Type	Also called	Build	Relative output	Typical depth
Type 10	Single panel, no fins	One panel	Lowest	About 50 mm
Type 11	K1 or single convector	One panel, one set of fins	Low to medium	About 60 mm
Type 21	P+ or double panel plus	Two panels, one set of fins	Medium to high	About 75 mm
Type 22	K2 or double convector	Two panels, two sets of fins	High	About 100 mm
Type 33	K3 or triple convector	Three panels, three sets of fins	Highest	About 160 mm

Depths vary by brand. Type 22 is the most common choice for living rooms, and Type 33 is often used for heat pump upgrades where wall space is limited.

Other radiator styles

Style	Best for	Things to know
Column	Period homes, open-plan rooms	Heavy, holds more water, may need floor feet
Vertical	Narrow walls, alcoves, kitchens	Can give less output than its size suggests
Aluminium	Fast warm-up, low water content	Usually more expensive, needs suitable inhibitor
Cast iron	Period character, slow steady heat	Very heavy, needs strong fixing and floor support
Flat panel designer	Modern look on show	Often lower output than a standard panel
Fan-assisted	Heat pumps and low-temperature systems	Needs a small electrical supply

How finish affects heat output

Finish makes more difference than many people expect. Chrome and polished metal finishes radiate heat less effectively than painted surfaces, so a chrome towel rail typically gives roughly 20 to 30 percent less heat than the same rail in white. Covering a radiator with a decorative cabinet, a shelf or long curtains also reduces the heat reaching the room.

Colour of paint makes very little difference; a black, grey or coloured painted radiator gives out much the same heat as a white one. Textured and matt painted finishes perform similarly to gloss. It is bare and plated metal that loses out.

Steel, aluminium and cast iron compared

Material	Warm-up speed	Heat retention	Weight	Typical cost
Steel	Medium	Medium	Moderate	Lowest
Aluminium	Fast	Low	Light	Higher
Cast iron	Slow	High	Very heavy	Highest

Steel is by far the most common because it is cheap, widely available in standard sizes and performs well. Aluminium heats and cools quickly, which suits rooms used in short bursts, but it reacts differently with water chemistry, so the system inhibitor must be suitable for mixed metals. Cast iron holds heat for a long time after the boiler switches off, which some people love in period homes, but a large cast iron radiator full of water can weigh well over 100 kg and needs floor-standing feet or very solid wall fixings.

Understanding output figures

Radiator outputs are tested to BS EN 442 and usually quoted at Delta T50, meaning the average water temperature is 50°C above a room temperature of 20°C. Some manufacturers quote Delta T60 or Delta T70, which gives a bigger number for the same radiator. When comparing radiators, make sure every figure is at the same Delta T, and remember that a system running cooler than Delta T50, such as a heat pump or a condensing boiler run at a low flow temperature, will get less than the headline figure.

Which type for which room

Living room: Type 22 panel or a multi-column radiator, sized to the heat loss
Bedrooms: Type 11 or Type 21 is often enough in a well-insulated room
Kitchen: vertical or compact Type 22 where wall space is taken by units
Bathroom: painted towel rail, or a towel rail plus a small radiator in a cold room
Hallway: Type 22 near the front door, as halls lose heat every time it opens
Heat pump homes: Type 22, Type 33 or fan-assisted radiators sized at the design flow temperature

Whatever the style, the radiator should be chosen from the heat the room needs first and the look second. It is common to find that a favourite designer radiator needs to be a size larger than expected, or that two smaller radiators on different walls heat a long room more evenly than one large one.

Connections and valve positions

Radiators connect in a few standard ways, and this affects whether a new radiator can drop straight onto the old pipework. Most panel radiators are bottom-opposite-end, with a valve at each lower corner. Some designer and towel radiators use bottom-centre or side connections, and many have the valves underneath rather than at the sides. If you are changing style, check the connection type and the valve centres against where your pipes come out, as altering pipework can add noticeably to the cost.

Bottom opposite end: the standard for panel radiators
Same end: both pipes at one end, used where only one side is accessible
Bottom centre: twin pipes close together, common on vertical and designer models
Side or top connections: found on some towel rails and older radiators