Degrees of Separation: Tackling Overheating in Schools
As the Met Office issues a rare Red Extreme Heat warning this week, overheating in schools needs treating as a planning priority, not a summer inconvenience — and there’s an affordable first step every school can take now.
This week isn’t a fluke
On 23 June 2026, the Met Office issued a Red Extreme Heat warning — its highest alert level, reserved for situations carrying a genuine risk to life — covering parts of central and southern England and Wales, with temperatures forecast to reach 38–39°C and the UK’s all-time June record (35.6°C, set in 1976 and 1957) expected to fall.
Some schools have already closed early or sent pupils home this week rather than keep classrooms occupied in temperatures often running several degrees hotter indoors than outside. That shouldn’t have to be a unilateral, building-by-building call made on the day — but for many schools, it is. As Paul Whiteman, general secretary of the National Association of Head Teachers, put it during this week’s closures: “there is no legal ‘upper limit’ for temperature in schools” — only guidance that school leaders do what they can to mitigate the effects.
The data behind the headline
It’s tempting to treat extreme heat warnings as freak weather. The Met Office’s own records say otherwise. The UK has warmed at roughly 0.25°C per decade since the 1980s, and the most recent decade (2015–2024) was 1.24°C warmer than the 1961–1990 baseline. Four of the last five years now rank among the UK’s top five warmest since records began in 1884.
The frequency of hot days is climbing faster still. Comparing the most recent decade to 1961–1990, the number of days exceeding 28°C — the recognised threshold for a ‘hot’ day in UK classrooms — has roughly doubled in many counties, with areas that once rarely saw a hot day now seeing them regularly. Met Office scientists have even modelled a plausible scenario reaching 45°C by 2056.
For estates teams, the implication is simple: a school built or refurbished for the climate of ten years ago is increasingly under-specified for the summers it now faces.
What overheating does to learning and teaching
UK guidance treats 28°C as the overheating threshold and 32°C as the limit not to be exceeded while a room is occupied — yet many single-aspect, heavily-glazed or top-floor classrooms exceed both on a hot day. The evidence is consistent:
- Pupils: concentration, memory and cognitive performance measurably decline above thermal comfort ranges, well below 28°C.
- Staff: heat fatigue and headaches in poorly ventilated rooms quietly push lessons towards low-effort, sedentary activity on the hottest days.
- Health: heat exhaustion and heat stroke are real risks, and children’s thermoregulation is less developed than adults’.
If heat has closed your school, record it like you would a boiler failure
A boiler failure leaving a school without heat or hot water in January is normally treated as a strong, evidenced case for capital intervention. A building becoming unsafe to occupy because it’s too hot deserves the same treatment. If your trust has a boiler replacement project earmarked for an upcoming CIF round, evidence of summer closures, restricted room use or recorded internal temperatures adds a second strand of justification alongside the winter heating case. Record dates, affected buildings and pupil or staff impact now, while it’s fresh, rather than reconstructing it closer to the bid deadline.
Quick win or long-term fix — there’s a solution either way
A quick, low-cost fix with an immediate payback
Large or poorly performing glazed areas are one of the biggest drivers of classroom overheating: glass lets solar gain in, then traps it. A non-combustible window coating, applied internally to existing glass — from heritage single glazing through to modern double glazing — is one of the most cost-effective fixes, and doesn’t depend on CIF funding, condition category, or trust eligibility at all. It’s something every school can consider now, this summer.
From the figures we’ve seen from suppliers in this space, the improvement is substantial. The coating blocks around 80% of incoming infrared heat and cuts overall heat gain by roughly 40%, taking a genuine bite out of summer overheating without changing natural light levels. In winter it works the other way, improving a single-glazed window’s heat retention by around 20% — a meaningful saving on heating bills for relatively little outlay. It also cuts condensation by about half, protecting frames, sills and internal finishes from the damp and mould that often follow a cold winter. And because it’s a genuinely non-combustible, interior-applied coating with a 20-year proven life and 10-year warranty, it’s a low-risk measure that can be fitted in a single school holiday — including in listed or heritage buildings, where it’s fully reversible.
Where a school does have a wider CIF-funded fabric or glazing scheme in progress, it’s also worth including as a line item within that bid rather than only treating it as a stand-alone measure.
If a boiler replacement is already on the cards
Where a school has a boiler replacement project in the pipeline, through CIF or a general scheme, it’s worth widening the brief beyond a like-for-like gas swap. Air-to-air heat pumps heat in winter and run in reverse to cool in summer — an advantage no boiler replacement offers. That benefit compounds with solar PV, since cooling demand peaks on the same bright days generation is highest, so cooling can run largely on free power. In winter, air-to-air systems are typically the simpler heat pump route for schools: high efficiency, room-by-room control, and far less design complexity than air-to-water systems.
Get in touch
Whether you’re weighing up a quick, affordable fix for this summer or building the evidence base for your next CIF bid, we’d be glad to talk it through. If your school is simply finding conditions unbearable right now — fielding complaints from pupils, staff and parents, with no end in sight — that’s reason enough to act, even before you get as far as a funding bid. Get in touch if your school has had to close, restrict room use, or send pupils home because of the heat this week.
