Loft conversion air conditioning
Loft conversion air conditioning that copes with the heat under the roof
Loft conversion air conditioning for the room that gets hottest of all. Olly picks the right unit for sloping ceilings and low walls, finds a tidy route for the pipes, and sets it up to heat the room in winter too. Across Dartford, Kent and south-east London, including lofts other firms have turned down.
The problem
Why a loft conversion gets so hot
A loft room sits right under the roof. On a sunny day the tiles or slates can get far hotter than the air, and that heat works its way down into the room all afternoon. Rooflights let the sun straight in. Warm air from the rest of the house rises up the stairs to join it. By evening, a loft bedroom can be the warmest room in the house by several degrees.
Good insulation slows the heat down but also slows it leaving, so the room stays warm well into the night. Opening the rooflights helps once it cools outside. It does very little at four in the afternoon in July.
Air conditioning takes the heat out and puts it outside. Because the units we fit are heat pumps, the same unit also heats the loft in winter, which is useful in a room the central heating often struggles to reach.
Choosing a unit
Which unit suits a loft with sloping ceilings?
The shape of the room decides the unit. These are the three options we use in loft air conditioning.
Floor-mounted
Sits low on a knee wall under the slope, where nothing else fits. It heats well because warm air starts at floor level, and the filters are easy to reach.
Floor-mounted unitsWall-mounted
Goes high on a gable or dormer wall, where there is enough upright wall and space above it for air to get in. Usually the simplest option.
Wall-mounted unitsDucted from the eaves
A slim unit hidden in the eaves or roof void, with only grilles showing. It can serve the loft and the rooms below, with Airzone zoning.
Ducted systemsPipe routes
Getting the pipes out of a loft
Most loft jobs that other companies call impossible come down to one question: how do the pipes get from the indoor unit to the outdoor unit? These are the routes we look at, in order.
- Straight out through the wall. If the indoor unit is on a gable or dormer wall, one core-drilled hole behind it is often all it takes.
- Through the eaves. Behind a knee wall there is usually a void. Pipes can run through it and come out low on the roof line, then down the wall in trunking.
- Down inside the house. Sometimes a cupboard or boxing on the floor below gives a hidden route to ground level.
Pipe length matters. Each outdoor unit has a maximum pipe run and height difference set by the manufacturer, and long runs can need extra refrigerant. We plan the route against those limits, so the system works as it should. The drain needs a steady fall to run outside. Where it can't fall all the way, we fit a small, quiet condensate pump.
Where the outdoor unit goes is the other half. A ground-level spot is easiest to service. A high wall bracket keeps pipes short but may need an access tower on the day. On a house in England, it cannot go on a pitched roof if you want it to stay permitted development. Our guide to planning permission for air conditioning sets out the rules.
A photo of the room and one of the outside wall is a good start.
Real jobs
Loft air conditioning that “couldn't be done”
A Dartford customer had been told by other companies that their loft could not have air conditioning. Access in the loft was the problem.
Olly found a way and fitted a split system. In the customer's words, Olly "made it look easy". A Google reviewer tells a similar story: two other companies said their install couldn't be done, and Olly "explained how it could be achieved".
Awkward routes are normal for us. In Bexleyheath we hung seven indoor units on two Mitsubishi Heavy Industries multi-splits, with what the customer called "lots of awkward trunking /pipe runs".
What size unit does a loft need?
Usually more than a room of the same size downstairs, because of the roof and the glass above it. A loft bedroom often needs a size up from the bedroom below it. The building regulations guidance (Approved Document L) says cooling should be sized from a heat-gain calculation, and we do one for every loft. It takes in the roof, rooflights, insulation and the direction the slopes face.
Cooling a bedroom on a lower floor too? See bedroom air conditioning.
Cost
How much does loft conversion air conditioning cost?
You get a fixed written quote after a free survey. As a guide, published UK figures for fitting one room usually range between £1,500 and £3,000 (MyBuilder and Selectra, 2026), and a loft with a long or awkward pipe route tends to sit nearer the top. What makes the difference in a loft:
- The pipe route: its length, the height drop and how much trunking it needs.
- Access for the outdoor unit, such as a tower for a high wall bracket.
- Floor, wall or ducted unit. Ducted needs builder's work for the grilles and ducts.
- A power supply up to the loft, and whether the drain needs a pump.
Our guide to how much air conditioning costs has the national ranges and where they come from. For everything else about fitting, see our main air conditioning installation page.
Our work
Neat outside, as well as in
Pipes from a loft often run down the outside wall, so the finish there matters.
Reviews
“Other companies had told me it couldn't be done”
Couldn't have asked for better service. The install was difficult and challenging due to access issues in loft. Olly made it look easy and dealt with everything in a professional and reassuring way. He went above and beyond as other companies had told me it couldn't be done. First rate job and top bloke.
Olly did a great job with our AC installation. We had 2 other companies look at it and said it couldn't be done. Olly explained how it could be achieved, quoted for it and promptly got it sorted. Nothing was too much trouble and we really felt he cares about what he does. Would highly recommend.
Questions
Loft air conditioning FAQs
Can you put air conditioning in a loft with sloping ceilings?
Yes. Sloping ceilings rule out some spots, not the room. If there is a gable wall or a dormer wall with enough height, a slim wall unit can go there. If the only upright wall is a low knee wall under the slope, a floor-mounted unit sits there instead. We look at both at the survey and show you where each would go.
How do I keep a loft conversion cool in summer?
Start with the free things: blinds or shades on the rooflights, windows shut and blinds down in the heat of the day, then open up at night to let the cooler air in. Good roof insulation helps too. In a proper heatwave none of that is enough under a sunny roof, which is when a heat-and-cool unit earns its place.
Can the outdoor unit go on the roof?
Not on a pitched roof if you want it to be permitted development: the rules for houses in England rule that out. A flat dormer or extension roof can work, as long as the unit is at least 1 metre from the edge and passes the noise check. More often it goes on a wall bracket or on the ground, with the pipes in neat trunking.
Should I fit air conditioning while the loft is being converted?
If you can, plan it in. Before the plasterboard goes up, it is often possible to run the pipes, cable and drain inside the walls or eaves, so nothing shows later. The units can then go on once the room is decorated. Send us the drawings and we will tell you where the pipes should run.
Can ducted air conditioning go in the loft?
Often, yes. If part of the roof space stays unconverted, such as the eaves or the void above, a slim ducted unit can sit there and feed grilles into the loft room or the bedrooms below. Add Airzone zoning and each room gets its own thermostat. It needs enough space for the unit and ducts, which we check at the survey.
Get a free loft air con quote
Talk to Olly directly. He quotes and fits the jobs himself.
Quickest way to a price: send on WhatsApp
- A photo of the room and the outside wall
- Your town and what you need
- For a repair, the unit's label and any error code
Free survey and a fixed written quote for new systems. No obligation.