Office Air Conditioning: A 2026 Guide for UK Businesses

Quick answer: what do UK offices need to know about air conditioning?

UK law does not require an office to have air conditioning, but the Workplace (Health, Safety and Welfare) Regulations 1992 do require employers to keep indoor workplaces at a "reasonable" temperature. The HSE Approved Code of Practice puts a floor of at least 16°C on sedentary work such as office work, and there is no legal maximum temperature. In practice, most UK offices are designed to hold roughly 21°C to 23°C, and air conditioning is the only reliable way to hit that through a Kent summer.

The rules on heat are also moving. In July 2026 the government confirmed that the HSE is reviewing the Approved Code of Practice behind those 1992 regulations, with a public consultation expected to look at whether a maximum recommended working temperature should be set. If your office is already uncomfortable in July, this is a good year to fix it properly.

This guide covers the temperature rules in plain English, the system types that actually suit offices, how to specify one without overpaying, and the compliance duties that kick in once it is installed.

Is air conditioning a legal requirement in a UK office?

No. There is no law that says an office must have air conditioning. There is a law that says the temperature must be reasonable, and that is a different thing.

Regulation 7 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires employers to maintain a reasonable temperature inside buildings during working hours. The Approved Code of Practice that sits alongside it says the temperature should normally be at least 16°C where the work is mainly sedentary, or 13°C where it involves rigorous physical effort. Those are guidance figures describing what "reasonable" usually means, not a hard statutory threshold.

For heat, there is no equivalent number. The UK has never had a legal maximum working temperature. That does not let employers off the hook, because the general duty to protect health and safety still applies, and heat stress is a recognised workplace risk. It simply means the responsibility sits with you to assess and control it.

Is that about to change?

Possibly. On 8 July 2026, during the UK's third heatwave of the year, ministers told Parliament that the HSE is progressing a wider review of the Approved Code of Practice for the 1992 regulations, including the sections on workplace temperature, to make sure it is fit for a modern workplace. A public consultation was announced for later in 2026, and it is expected to consider setting clear thresholds for a maximum recommended working temperature.

Unions including the TUC and Unison have called for a legal indoor maximum of 30°C, or 27°C for strenuous work, and a parliamentary petition for a 25°C limit gathered thousands of signatures over the same week. Nothing is settled, and we would not advise anyone to install a system purely on the basis of a consultation. The context matters though: the Met Office confirmed that by early July 2026 the UK had already recorded eight days at 34°C or above, the highest number on record. Offices that were bearable a decade ago are not bearable now.

What temperature should an office be?

There is no single legal answer, but there is a well-established comfort range. Most people working at a desk are comfortable somewhere between 20°C and 24°C, and building services engineers typically design office cooling to hold around 21°C to 23°C.

Comfort is not just about the number on the thermostat either. Humidity, air movement, what people are wearing and how much sun a window gets all affect how warm a room feels. A south-facing meeting room with floor-to-ceiling glass can be five degrees warmer than the open-plan floor next to it, which is exactly why zoned control matters more in offices than in homes.

A practical rule of thumb: if staff are propping doors open, bringing in desk fans or asking to work from home on hot days, your building is telling you something before anyone files a complaint.

Which air conditioning system is best for an office?

The right answer depends far more on your floor plan than on your budget. Here is how the main options compare for office use.

For most Kent offices we survey, the answer is a mix. Cassettes across the open-plan area, a wall-mounted unit in the server room that runs year round, and separate control for meeting rooms that only get used part of the week.

For the full price breakdown across all of these system types, see our guide to commercial air conditioning costs. If your office is more of a house-sized space with a few rooms, the comparison in our single split vs multi-split guide is a useful shortcut.

How do you size air conditioning for an office?

Sizing is where office installations most often go wrong, in both directions. An undersized system runs flat out and never quite gets there. An oversized one short-cycles, wastes energy and leaves the air clammy because it is not running long enough to dehumidify.

A proper survey adds up the heat load in your space, not just the floor area. That includes:

• People. Every occupant gives off roughly 100W of heat at rest. A 20-person floor is a 2kW heater before you switch anything on.
• IT and equipment. Monitors, laptops, printers and comms cabinets all add load. Server rooms are usually a separate calculation entirely.
• Lighting. Older lighting adds meaningful heat. LED retrofits reduce it.
• Glazing and orientation. Solar gain through south and west-facing glass is often the single biggest factor in a modern office.
• Insulation and air tightness. A converted Victorian building and a new-build unit on an industrial estate behave very differently.
• Occupancy patterns. Hybrid working means the floor may be full on Tuesdays and quiet on Fridays, which is an argument for zoning rather than one big system.

Be wary of any quote produced over the phone without a site visit. Office heat loads are too variable for a guess to be safe.

What compliance duties come with office air conditioning?

Once the system is in, two ongoing legal duties apply to almost every commercial installation.

F-Gas regulations. The refrigerant inside your system is a fluorinated greenhouse gas. By law, only an F-Gas certified engineer can install, service or decommission it, and systems above a set refrigerant charge need documented leak checks at fixed intervals, with records kept. Our full explainer is here: F-Gas regulations for UK businesses.

TM44 inspections. Under the Energy Performance of Buildings Regulations, buildings with air conditioning of more than 12kW total effective rated output must have a TM44 energy inspection by an accredited assessor at least every five years, with the report lodged on the national register. The 12kW threshold applies to the combined capacity across the building, not to each unit, so four 3.5kW wall units in a small office already put you in scope at 14kW. This catches out a lot of smaller businesses who assume the rules are only for large buildings.

Both duties are far easier to stay on top of with a planned commercial maintenance agreement, which also protects your warranty and your running costs. Our guide to how often air conditioning should be serviced covers the schedule in more detail.

Do you need planning permission for office air conditioning?

Usually not, but it depends on the building. External condenser units on commercial premises often fall under permitted development, with limits on size, siting and noise. Listed buildings, conservation areas and properties in a shared or town-centre setting are the common exceptions, and noise levels at the nearest residential boundary are frequently the sticking point in Kent town centres. We cover the detail in our guide to air conditioning planning permission.

How long does an office installation take, and how disruptive is it?

A single wall-mounted unit is typically a one-day job. A small multi-split across a few rooms is usually two to three days. A full open-plan floor with several cassettes and new pipework tends to run three to five days, and larger VRF projects are phased over one to several weeks depending on the building.

Disruption is manageable if it is planned. Most of the noisy work is core drilling and pipework routing, which can often be scheduled for evenings, weekends or a quiet week in the calendar. Booking outside the summer peak also helps: lead times and installer availability are far better between autumn and spring, which we explain in our guide to the best time to install air conditioning.

Book an office air conditioning survey in Kent

If your office is uncomfortable in summer, or you are fitting out new premises and want the cooling designed in rather than bolted on afterwards, the right starting point is a site survey.

All Kent Cooling is a family-run, F-Gas registered contractor based in Rochester, with over 25 years of experience installing office air conditioning for businesses across Medway, Maidstone, Ashford, Canterbury and the wider Kent and London area. We size the system to your building, explain the options in plain English and look after it afterwards.

Visit our commercial air conditioning installation page for a free, no-obligation quotation, or call 01634 541401 and we will arrange a survey around your working day.

Frequently asked questions

Is there a maximum office temperature by law in the UK?

No. The UK has no legal maximum working temperature. Employers must keep indoor workplaces at a reasonable temperature under the Workplace (Health, Safety and Welfare) Regulations 1992 and must manage heat as a health and safety risk, but no specific upper figure is written into law. The HSE announced a review of the relevant Approved Code of Practice in July 2026, with a public consultation expected to consider recommended maximum thresholds.

What is the minimum temperature for an office in the UK?

The HSE Approved Code of Practice says the temperature in workplaces should normally be at least 16°C where the work is mainly sedentary, which covers most office work, or at least 13°C where the work involves rigorous physical effort. These are guidance figures rather than an absolute legal limit.

What is the best air conditioning system for an open-plan office?

Ceiling cassettes are usually the best fit for open-plan offices. They sit flush in the ceiling, distribute air in four directions for even coverage, and avoid the draughts you get when a wall unit blows directly across desks. Larger or multi-floor buildings are often better served by a VRF system with zoned control.

Does office air conditioning also provide heating?

Yes. Almost all modern commercial systems are heat pumps, so the same equipment heats in winter and cools in summer. For many offices that makes the system a year-round asset rather than something that sits idle for nine months, and it often runs more efficiently than older electric or gas heating.

Do small offices need a TM44 inspection?

Possibly. The TM44 requirement applies to buildings with a combined air conditioning capacity above 12kW, measured across the whole building rather than per unit. Four 3.5kW wall-mounted units total 14kW and are therefore in scope, so plenty of small offices qualify without realising it. Inspections are required at least every five years by an accredited assessor.

How much does office air conditioning cost?

As a 2026 guide, a single wall-mounted unit for one office typically starts around £1,800 installed, a multi-split for a few rooms runs roughly £5,000 to £12,000, and ceiling cassettes for open-plan space start from about £2,500 per cassette. Larger VRF systems for whole buildings start around £15,000. Our commercial air conditioning cost guide breaks it down system by system.