Heating Sizing Pack

Why the radiators that were fine on a boiler leave the house cold on a heat pump

Every radiator on sale is advertised at one output, and that figure is the EN 442 laboratory condition: 75/65°C into a 20°C room. Output falls with temperature difference to the power of 1.3, so at a heat pump's 45/40°C the same radiator gives about a THIRD of its badge figure. That is the entire failure mode of a heat pump retrofit — the heat loss calculated correctly, the pump sized correctly, and the radiators never re-checked. This is the correction for every system temperature, the radiator you must actually buy for a given room load, the ways to fix a short room ranked cheapest first, the fabric measures that come before any of it, and where the work stops being yours by law. 8 pages, printable, ending in a room-by-room schedule you hold a quote against.

What’s inside

Where heating work stops being a homeowner's job, and what is theirs to do

The order of work for sizing a heating system, and what to settle before getting quotes

Fill-in room-by-room radiator schedule to hold an installer's quote against

Radiator output correction for six real system temperatures
Why a 1000 W radiator gives about 350 W on a heat pump
The radiator you must BUY for a given room load, at every flow temperature
The same room on a boiler and on a heat pump, side by side
Five ways to fix a short room, cheapest and least disruptive first
The honest fallback nobody sells you: raise the flow temperature
Fabric measures that come before sizing anything, and which are poor value
Seven sizing rules, including why a boiler's size tells you nothing
Where heating work stops being a homeowner's job — and what is yours
The question that tells you whether an installer has actually sized the job
The order of work, and three things to settle before getting quotes
Fill-in room-by-room radiator schedule

Plus a second PDF, worked out for you

Run one of the free calculators first and buy from that page, and this sheet is computed from your own figures. Buy from here and the pack still arrives complete — the sheet simply has no numbers of yours to work from yet.

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$1.99 including any taxes · PDF, 8 pages · instant download, link valid 7 days and 5 downloads.
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