UK Standard

BS EN 442 — Radiator Heat Output

BS EN 442 — Radiators and convectors

In short: BS EN 442 is the European standard for testing and publishing radiator heat outputs at Delta T50 (mean water temp 75°C, room temp 20°C).

What BS EN 442 covers

Since 2014, all UK radiators must be tested and rated to BS EN 442 at ΔT50, so catalogue BTU/watt ratings are directly comparable between manufacturers.

For heat pumps, which run cooler, the ΔT30 declaration applies — a radiator delivers far less than its ΔT50 output at lower flow temperatures, so it must be sized up.

Matching a radiator's ΔT50 catalogue output to a calculated room heat loss is the core of correct sizing.

Apply this standard

Calculators that use BS EN 442

Radiator BTU Calculator
Room heat loss using the CIBSE method with radiator sizing and ASHP correction factor.
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Official source: BSI Knowledge — BS EN 442. Figures on this page are a plain-English summary for estimating purposes — always refer to the published standard for compliance.