Air Conditioning for Small Offices: A Complete Buyer's Guide
UK working temperature regulations, equipment heat loads, lease considerations and the right system types for offices up to 20 people.
Air conditioning in a small office is not just a comfort measure — in the UK it's increasingly a legal obligation and a productivity tool. Here's what you need to know before specifying a system.
UK workplace temperature regulations
The Workplace (Health, Safety and Welfare) Regulations 1992 require employers to maintain a 'reasonable' temperature in the workplace. The Health and Safety Executive (HSE) recommends a minimum of 16°C for sedentary work, with no absolute maximum specified. However, the HSE has published guidance that indoor temperatures above 24°C trigger the right for a workplace risk assessment.
In practice, employers have a duty to keep temperatures comfortable, and a small modern office can reach 28–30°C on a hot summer day without air conditioning. The resulting productivity loss, discomfort and potential for heat-related illness creates real business risk.
Calculating the cooling load for an office
Offices generate significantly more heat per square metre than domestic rooms because of:
- •Computers, monitors and networking equipment (each workstation generates 150–300W)
- •Higher occupancy (each person adds approximately 100W of sensible heat load)
- •Lighting (LED reduces this, but older fluorescent lighting adds significantly)
- •Printers and other office equipment
A 6-person office with modern computers and monitors may generate 1.5–2.0kW of equipment heat alone, before accounting for the building heat gain. This significantly increases the required system capacity compared to a domestic room of the same size.
System options for small offices
For offices up to approximately 40m², a single high-capacity split system (typically 5.0–7.0kW) is usually the most cost-effective solution. For larger open-plan spaces, a multi-split system with ceiling cassette units offers better air distribution and a cleaner aesthetic than wall-mounted units.
Lease considerations
If your office is leased, you'll typically need landlord consent before installing air conditioning. You may also have an obligation to reinstate the property on vacating. It's worth clarifying these terms before committing to an installation — ideally getting written consent that specifies whether reinstatement will be required.
Tax treatment
Air conditioning installed in a business property may qualify as a capital allowance under the Annual Investment Allowance (AIA), potentially allowing the full cost to be deducted from taxable profits in the year of installation. Your accountant can advise on the specific treatment for your circumstances.