Garden offices, studios, gyms and summerhouses are often lightweight buildings with a lot of glass. They heat up fast in the sun and lose heat fast in winter. A reversible air conditioning system, which works as an air-to-air heat pump, is one of the most popular ways to make them usable all year.
This guide covers the building itself, where the outdoor unit goes, the electrical supply, condensate, sizing, planning and what an installation costs.
Start with the building
Air conditioning works best in a building that holds onto what it’s given. Check that the walls, roof and floor are insulated, that doors and windows seal and that there’s shading on the sunniest glass. A poorly insulated summerhouse will need a much bigger unit and cost more to run. If you’re still planning the room, ask the builder to allow for air conditioning: a reinforced wall for the indoor unit, a pipe sleeve and a power supply.
Where the outdoor unit goes
Beside the garden room is usually simplest: a short pipe run, the outdoor unit on a ground pad or bracket on a solid wall. Think about the neighbours’ gardens and windows, because garden rooms are often near boundaries.
At the house, with pipework run underground or along a fence to the garden room, can keep the unit out of sight. Underground runs need the pipes in a protective duct and a proper trench. Every model has a maximum pipe length and height difference, which we check.
Our guide on where to put the outdoor unit covers clearances.
Power to the outbuilding
Many garden rooms already have a supply, but it may not have the spare capacity for air conditioning. A new or upgraded supply usually means an armoured cable from the house, a small consumer unit in the garden room and the right protection. This is notifiable work under Building Regulations Part P unless done by a registered competent person, and the Planning Portal’s electrics page explains the role of competent person schemes. Our electrical work is done under our NICEIC approval and certified.
Condensate and humidity
In cooling mode the indoor unit produces water, which needs to drain outside to a soakaway or gully, not onto a path or against the timber frame. In heating mode the outdoor unit drips, so position it where that water won’t turn to ice on a step. Garden gyms and studios with people exercising also produce moisture; dry mode can help, but ventilation matters too.
Want it done properly? AirCon Doctor installs, repairs and services air conditioning and heat pumps across London and the South East, from our base in East Grinstead. We’re an F-Gas certified company and NICEIC approved. Get a fixed-price quote.
Sizing
Garden rooms are small, but with lots of glass and lightweight walls they can need more capacity than a similar room in the house. We size from the floor area, height, glazing, orientation, insulation and use. A gym needs more cooling than an office of the same size. Our sizing guide explains the factors.
Heating all year
The same unit heats in winter, which is often the bigger benefit in a garden office. It responds quickly and can run on a schedule, so the room is warm when you start work. See using heat pump mode in winter.
Planning
An air conditioning unit used only for cooling isn’t covered by permitted development and needs checking with the council. A heat pump used for heating can be permitted development on a house if it meets the Planning Portal’s conditions, including MCS 020(a) noise compliance. Rules for outbuildings and boundaries vary with the site, so check with the council if the unit will be near a boundary or the property is listed or in a conservation area.
What it costs
A single room split system costs £1,200–£2,200 + VAT, including supply, installation, commissioning and F-Gas documentation. Long or underground pipe runs and electrical supply upgrades are priced after the survey, and we list them separately on the fixed-price quote. See our home office guide for working-from-home tips.
Quick answers
Can you fit air conditioning in a garden office?
Yes. A wall-mounted split system with the outdoor unit beside the building or at the house is the usual choice, and it heats as well as cools.
Does my garden room need its own electrical supply?
Often an upgraded supply is needed. We check at the survey, and any new circuit is certified under our NICEIC approval.
Can the outdoor unit be by the house instead?
Often, yes, with the pipework run in a protective duct. Each model has a maximum pipe length we must stay within.
Will it work in winter?
Yes. A reversible system is an air-to-air heat pump, so it can heat the garden room efficiently in cold weather.
Related services
- Air conditioning installation
- Wall-mounted air conditioning
- Air-to-air heat pumps
- Domestic air conditioning
More advice
- Air Conditioning for a Home Office: Complete Guide 2026
- Where to Put an Air Conditioning Outdoor Unit
- Air Conditioning Electrics: New Circuits and Part P
- Air Conditioning in Winter: Using Heat Pump Mode Effectively
- All advice
This guide is general information, checked against the sources linked on 30 October 2026. It isn’t legal, tax or financial advice. Rules, grants and product ranges change, so check the current position before you rely on it.