Type 21 Radiators (Double Panel/Single Convector)

A Type 21 radiator has two panels and a single convector fin — the sensible middle ground in the compact radiator range. More heat than a Type 11, less projection into the room than a Type 22.

Where a Type 21 makes sense

At roughly 70mm deep it sits between the two, which suits hallways, landings and bedrooms where you want reasonable output without a bulky radiator sticking out from the wall. In a narrow space, that 30mm saved over a Type 22 is worth having.

Comparing the types

• Type 11 — slimmest at around 50mm, lowest output.
• Type 21 — around 70mm, moderate output.
• Type 22 — around 100mm, highest output for the size.

Getting the size right

Calculate the room's BTU requirement rather than copying the old radiator — heating needs change with insulation, glazing and extensions. Quoted outputs assume a 50°C temperature difference, so expect less from a low-temperature or heat pump system.

Most radiators are supplied without valves, so add those to your order.