Every radiator specification sheet carries the same four terms: BS EN 442, Delta T, BTU, Watts. They appear in specifications, procurement schedules, and M&E design drawings — often without explanation. For estates managers, facilities teams, and anyone buying or specifying heating for the first time, the numbers can feel more like gatekeeping than guidance.
They aren't. Each value tells you something specific and useful. This guide covers what the terms mean, how they connect, and why accuracy is important in NHS and healthcare settings where heating performance has to be precise, not approximate.