Office temperature rules in the UK: what employers must know
Every summer we get calls from office managers convinced there must be a law setting a maximum workplace temperature, and every summer we have to explain that there isn't one. The Workplace (Health, Safety and Welfare) Regulations 1992 require a 'reasonable' temperature, without putting a number on it, which leaves employers carrying the judgement call themselves.
That vagueness causes real problems. Staff assume there's a legal trigger point at which they can go home, managers assume compliance means nothing more than opening a window, and meanwhile the top floor of a glass-fronted office in Hemel Hempstead or Watford can sit at 30 degrees by mid-afternoon in June. This guide sets out what the rules actually require and what practical steps close the gap.
What the regulations actually say
The Approved Code of Practice attached to the 1992 regulations suggests a minimum of 16 degrees Celsius for most workplaces, or 13 degrees where the work involves severe physical effort. There is deliberately no maximum figure, because the Health and Safety Executive recognises that 'reasonable' depends on the type of work, the clothing expected, and the humidity and airflow in the space, not a single number that suits every building.
What employers are required to do is assess the risk. That means considering whether heat is making the workplace unsafe or intolerable, not simply uncomfortable, and taking reasonably practicable steps to address it. A stuffy office with tired staff isn't automatically a breach; an office where people are at risk of heat stress, dizziness or dehydration is a different matter entirely.
Where employer duties actually bite
The duty becomes harder to avoid once temperature starts affecting health rather than just comfort. Persistent headaches, staff being sent home unwell, or visibly poor concentration and error rates in hot conditions are the kind of evidence that would matter if a complaint were ever escalated to the HSE or an employment tribunal. Employers are expected to have thought about ventilation, shading and cooling as part of general risk assessment, not to have waited for a formal complaint.
This is also where reasonable adjustments for specific individuals come in, particularly for pregnant employees or those with underlying health conditions that make heat riskier. A generic office-wide policy on hot weather doesn't remove the separate duty to consider individual circumstances when they're raised.
Why 'open a window' isn't always the answer
Many older UK offices rely entirely on openable windows and desk fans, which move hot air around without actually cooling it. On days when outside temperature exceeds inside temperature, opening windows makes things worse, not better. Glazed, south-facing offices in particular can trap solar gain that no amount of natural ventilation will shift.
Fans also do nothing for humidity, and a humid office feels considerably hotter than a dry one at the same temperature. Mechanical cooling is the only reliable way to bring both temperature and humidity under control at the same time, which is why more offices are moving from 'we'll manage with fans' to a proper air conditioning installation once summers start affecting productivity year after year.
Practical steps that reduce risk and complaints
- Fit blinds or solar film to south and west-facing glazing to cut solar gain before it enters the room.
- Relax dress codes on genuinely hot days rather than relying on this as the sole response to overheating.
- Provide accessible drinking water and encourage regular breaks in cooler areas during heatwaves.
- Monitor temperature with a simple thermometer in the worst-affected areas rather than guessing.
- Where heat is a recurring seasonal problem rather than a one-off, treat mechanical cooling as the long-term fix rather than a series of short-term workarounds.
When to consider air conditioning rather than managing around the problem
If the same complaints come up every summer, if staff are working below their usual output on hot afternoons, or if you're relying on portable units dragged out of a cupboard each June, it's worth treating the underlying issue rather than the symptoms. A correctly sized split or multi-split system, designed around your floor plate, occupancy and glazing, removes the guesswork and the annual scramble.
We regularly survey offices across Hertfordshire, Bedfordshire, Buckinghamshire, Essex and north-west London where the existing approach has been fans and good intentions. A short site visit is usually enough to show what a properly designed system would cost and how quickly it pays for itself in reduced disruption. If office temperature is becoming a recurring issue for your business, get in touch for a free quote and we'll talk through the realistic options for your building.
FAQs
Common questions
Is there a legal maximum temperature for UK offices?
No. The regulations set a minimum of 16 degrees Celsius but deliberately don't set a maximum, focusing instead on a general duty to keep temperatures reasonable.
Can staff legally refuse to work if the office is too hot?
There's no automatic right to leave once a specific temperature is reached, but employers must act if heat creates a genuine health and safety risk rather than mere discomfort.
Do employers have to provide air conditioning?
Not specifically, no single method is mandated. Employers just need to show they've taken reasonably practicable steps to keep the workplace at a reasonable temperature, which air conditioning is often the most effective way to achieve.
What should I do first if my office is too hot every summer?
Start with shading and ventilation improvements, but if the problem repeats every year, get a proper survey done so you understand what a permanent cooling solution would cost.
Does the temperature rule apply to home workers too?
The 1992 regulations apply to workplaces the employer controls, so home offices sit outside them directly, though general duty of care principles still encourage sensible support for home-based staff.
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