Can you fit air conditioning in a flat or apartment?

Flats often get hotter than houses, and they are harder to fit. Most of the difficulty has nothing to do with the air conditioning itself. It comes down to who owns the outside of the building, and what they will let you fix to it.

Who has to agree before air conditioning goes in?

In a leasehold flat, which is most flats in England, you own the inside of your home and the freeholder owns the structure: the outside walls, the roof and often the balconies. Almost every lease needs the freeholder's or managing agent's written consent before anything is fixed to the outside or a hole goes through an outside wall. That consent is often called a licence for alterations.

What they normally want to see is the equipment, where the outdoor unit would sit, its size and noise rating, how the pipework reaches it, and how the hole through the wall will be sealed. We put that information together at survey, because a vague request is the quickest way to a refusal. Some freeholders charge a fee to process a request, which they set, not the installer.

If you rent, you also need your landlord's written permission, and your landlord will usually need the freeholder's consent in turn.

Do I need planning permission for air conditioning in a flat?

Usually not, in England, and planning is rarely the hurdle. The lease is. Permitted development covers flats as well as houses, but with tighter limits, and the noise standard still applies: 42 dB(A) at the nearest window of a room a neighbour lives in. Whether a particular position qualifies depends on the building, so we check it at survey.

Two cases change the picture. A listed building needs listed building consent for anything fixed to it, whatever the lease says. In a conservation area the outdoor unit has to stay away from the road side of the building. The full planning rules set out every condition. Scotland, Wales and Northern Ireland have their own rules.

Where does the outdoor unit go in a flat?

There are three usual positions, and the building decides which is possible:

• On a balcony, standing on its own feet or a low bracket. On a modern block this is usually the easiest route, and it keeps the pipe run short.
• On an outside wall, on brackets, where the freeholder agrees. Often only possible on the lower floors or at the back of the building.
• On a flat roof or in a shared plant area, agreed with the building manager. Common in blocks that allow nothing on the outside walls, and for top floor flats.

A balcony unit needs open air around it to get rid of the heat it takes out of your flat. An enclosed, glazed winter garden traps that heat, so it is not a suitable place for one.

What if the building will not allow an outdoor unit?

Then there are two realistic options.

A self contained unit with no outdoor part. The whole machine sits inside, high on an outside wall, and breathes through two round holes of roughly 16 to 20 centimetres, which finish outside as small grilles. Freeholders who refuse an outdoor unit will often agree to this, though the holes still need their consent. The trade off is that the compressor is in the room with you, so it is louder than a split system and less efficient, and it suits a bedroom or study rather than a large open plan living room.

A portable air conditioner. It needs no consent, which is its one real advantage. A single hose portable pushes room air out through the window hose and pulls warm air back in through the gaps to replace it, so it cools noticeably less than its label suggests, and it is noisy in the room. Where the windows only open a few inches for safety, the hose often does not fit properly either.

My flat has MVHR. Is that air conditioning?

No. Many newer apartments have mechanical ventilation with heat recovery, which swaps stale air for fresh and holds on to the heat in winter. Its summer bypass lets outside air in without warming it, but a standard system cannot make the air colder than it is outside, so on a hot afternoon it does not cool the flat.

It is still worth running and keeping serviced, because a well ventilated flat is easier to keep cool. The ventilation page covers how it works alongside cooling.

Why do flats overheat so much?

Three things tend to stack up. Large areas of glass with little shading. Windows that only open a few inches for safety, so there is almost no breeze through the flat. And heat arriving from the homes around and below you, as well as from outside. Many apartments also face one direction only, so there is no cooler side of the flat to open up, and a top floor flat takes heat from the roof as well.

What about Manchester's converted mills and apartment towers?

Apartments in Manchester city centre and Salford Quays tend to fall into two groups, and each has its own catch.

Converted mills and warehouses, in areas such as Ancoats and Castlefield, are often listed or sit in conservation areas. The outdoor unit usually has to go somewhere out of sight, and listed building consent may be needed. The walls are thick masonry, which is slow to drill through but good at holding a steady temperature.

Newer towers are often glazed on one side, with balconies or winter gardens, and a building manager with firm rules about the outside. A balcony is usually the way in. In taller blocks, anything that passes through an outside wall must keep the building's fire protection intact, so expect the building manager to ask exactly how the hole will be sealed.

There is more on each area on the Manchester and Salford pages.

Will the neighbours hear it?

In a flat your neighbours are above, below and beside you, so the position matters more than it does in a house. The noise standard is measured at the nearest window of a room a neighbour lives in, and most leases also forbid causing a nuisance. A balcony unit on anti vibration feet, away from the neighbours' bedroom windows and running its quiet night mode, is normally fine. We work out the noise at the nearest window for the proposed position at survey.

Where does the water go?

Every indoor unit takes water out of the air as it cools, and that condensate needs somewhere to drain. In a house it usually runs to a drain outside. In a flat it often joins an internal waste pipe, such as the kitchen sink or washing machine waste, through a trap, or a small pump lifts it where gravity will not. The route is planned at survey, so nothing drips onto the balcony below.

What size unit does a flat need?

Often smaller than the floor area suggests. A flat in the middle of a block shares its floors, ceilings and walls with homes that are heated and cooled too, so far less heat passes through them than through an outside wall. The exceptions are top floor flats, which take heat from the roof, and flats with a wall of south or west facing glass, which can need a size up.

The size calculator gives you a starting figure, and the survey confirms it.

What does it cost?

A single room starts at £1,850 fitted and a multi split for two to five rooms at £3,450 installed, with no VAT to add until 31 March 2027. In a flat, the things that move the price are where the outdoor unit can go, the route the pipework has to take, and access above the ground floor. Any fee the freeholder charges for consent is separate and set by them. The domestic price list has the rest, and if you live in a house instead, the terraced house guide covers the rules there.