Workplace heat: what UK employers actually need to know

Every UK heatwave produces the same two headlines: "Is it too hot to work?" and a wrong answer going viral. Here's what the rules actually say, and what competent employers do about it.

The legal position, plainly

There is no statutory maximum workplace temperature in the UK. The Workplace (Health, Safety and Welfare) Regulations 1992 require indoor workplace temperature to be "reasonable"; the Management of Health and Safety at Work Regulations require you to risk-assess heat like any other hazard. The HSE's guidance is explicit that thermal comfort must be assessed and managed — and an office at 30°C+ is not managing it.

"No legal maximum" is not a permission slip. It means the duty is outcome-based: if heat is making staff unwell or errors more likely, you're expected to act, and employment tribunals and HSE inspectors treat persistent inaction accordingly. Sector rules can be stricter in practice — care settings (CQC expectations around resident welfare in heat), food premises (stock and hygiene temperatures), and server/plant rooms all carry their own consequences for getting this wrong.

What "acting" looks like, in escalating order

1. Measure. A £15 logger per floor beats arguments. Track peak afternoon temperatures for a week.
2. Cut solar gain. Blinds down before the sun hits, not after. External shading on south/west glazing where the lease allows.
3. Manage internal gains. Dense banks of monitors, printers and kitchen kit add kilowatts. Consolidate, switch off, relocate.
4. Ventilate intelligently. Night purge if your building can do it; cross-ventilation in the morning; doors wedged (where fire strategy allows — check first).
5. Flex the people. Earlier starts, relaxed dress code, rotate away from hot zones, more breaks, cold water freely available. Cheap, fast, visible.
6. Cool actively. When the above tops out — most UK offices during an amber alert — you're into portable or installed cooling.

Portable vs installed for business

Portable units deploy in a day, need no landlord consent, and can follow the heat around the building. For a 40–60 m² open-plan zone you're realistically into multiple units (size with our calculator, then round up for occupancy and equipment). Their weaknesses — noise around 55–65 dB and a hose needing a window or ceiling-void route — matter more in meeting rooms than open plan.

Installed systems are the answer for premises you'll occupy beyond a couple of summers: quiet, efficient, heating in winter, and no annual scramble. They need landlord consent in leased premises and an F-Gas certified installer — lead times that argue strongly for arranging cooling in spring, not July.

Rental fits seasonal peaks and events: hospitality terraces, exam halls, temporary kitchens.

The care-setting note

If you operate a care home or supported housing: heat is a resident-safety issue with regulatory teeth. Overheating incidents feature in CQC reports every hot summer. Cooling plans, cool rooms, and monitoring are increasingly treated as expected practice, not gold-plating. Prioritise accordingly — and if you're arranging provision, our business cooling route flags care settings for priority handling.

Do the maths before July

A single lost-productivity afternoon across a 20-person office costs more than a good portable unit. Two summers of equipment rental at panic prices costs more than owning. The pattern is always the same: the organisations that sort cooling in April get spring prices and calm installation diaries; the ones that wait get heatwave premiums and three-week waits.

We built business priority reservations for exactly that first group. £10 per requirement, refundable, and your sites are scoped before the first alert of the summer.