About this site
Who writes this
Swelter is written by David White and published by Kabooly Ltd, in Kingston upon Thames, United Kingdom.
The author
Twenty years building digital products, for companies from startups to Telegraph Media Group, DAZN and TUI. Founder of Kabooly, which makes CRM software for small British businesses. Lives in Kingston upon Thames, in a house that gets uncomfortably warm in July, which is how this site started. Not a building services engineer, and this site does not pretend otherwise: what it offers is its own data, its sources, and a note wherever a figure is still unverified.
Why it exists
British housing was built to hold heat in. Solid brick, small windows, dark roofs, loft conversions, and a decade of insulation retrofits optimised entirely for winter. That was a sensible thing to optimise for, until it stopped being the only thing that mattered.
Building Regulations Part O deals with overheating in new builds. It does nothing for the twenty eight million homes that already exist. Those homes get magazine listicles and product roundups, almost none of it specific to the UK and almost none of it numerate.
This site is the other thing. Work out the number first, then decide what to buy, or whether to buy anything at all.
How it works
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Tools before articles
The calculators and the data are the point. The writing hangs off them. No article ships here without either a link to a tool or a number this site produced itself.
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Its own numbers
The town pages are computed from daily weather readings going back to 1950, stored and processed here. They are not forecasts and they are not borrowed from anyone's summary.
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Sources, or nothing
Where a legal rule, a price or a specification is not verified against a named source, this site says so on the page rather than publishing a plausible looking figure. Provisional means provisional.
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Willing to say no
Sometimes the honest answer is that a machine will not fix it, or that the cheap option is a portable unit, or that shading the window beats cooling the room. Those answers are worth as much as the other kind.
What is built so far
- Room cooling calculator
How much heat a room actually gains, where it comes from, and whether a machine is the answer at all.
- Running cost calculator
What a cooling unit costs to run, per hour, per night and per summer, in pounds.
- Can I install air conditioning here?
Whether a unit is permitted development in England under Class G, including the cooling only trap that most sites miss.
- Live weather warnings
Every Met Office severe weather warning in force across the UK right now, heat and cold alike, in their own words.
- The unit database
Every unit on published specification alone. No scores, no star ratings, nothing tested.
The rest are listed on the tools page, marked as not built yet rather than linked to nothing.
What this site is not
It is not medical advice and it is not legal advice. The planning tool tells you what the legislation says; it cannot see your property and it is not a substitute for asking your local planning authority. Anything about heat and health is general guidance, not a diagnosis.
It has also tested nothing physically, which the disclosure page explains in full.