Conservatory Air Conditioning: Size for the Glass, Not the Floor
A conservatory can be the hardest room in a UK house to cool and heat. Compare realistic installed costs, system positions and the survey details that prevent an undersized unit running flat out.
Why conservatories defeat ordinary sizing rules
Glass admits solar heat and usually insulates less effectively than a solid wall or roof. A south- or west-facing conservatory can gain heat just as the outdoor temperature peaks; in winter the same envelope loses heat quickly. The open doorway to the house can add another large, unpredictable load.
That is why “multiply square metres by a number” is only a rough screening tool. A useful calculation records roof material, glass area and specification, orientation, shading, air leakage, occupancy, adjacent rooms and the indoor temperature you expect on the design day.
Air conditioning can make the room genuinely usable, but it should be the active part of a wider heat-control plan. Roof blinds, external shading, solar-control film where suitable, insulated roof upgrades and closing the conservatory off from the house can reduce the unit size and running hours.
Illustrative capacity ranges—not a substitute for a survey
These bands show why a conservatory often needs more capacity than a normal room of the same floor area. They deliberately overlap because glass and orientation can move the answer by a full equipment size.
| Conservatory example | Capacity worth assessing | Main variable |
|---|---|---|
| Small, shaded, modern glazing | 2.5–3.5kW | Roof type and door to house |
| Typical 15–20m² glazed room | 3.5–5.0kW | Orientation and solar shading |
| Large or strongly south-facing space | 5.0–7.0kW+ | Glass load can dominate floor area |
| Open-plan conservatory + kitchen | Project calculation | Combined volume and cooking load |
If an installer proposes a size without asking which way the glass faces, whether roof blinds are used and whether the doors stay open, the answer is not yet a design. Ask for the calculated peak cooling and winter heating loads.
Which indoor unit fits all that glass?
| Indoor type | Where it fits | Trade-off |
|---|---|---|
| Low-wall console | Dwarf wall below glazing | Good fit and heating airflow; premium equipment price |
| High-wall split | Original house wall or solid end wall | Broad choice and low cost; needs clear wall area |
| Ceiling cassette | Larger orangery with ceiling void | Even distribution; needs void, drain pump and access |
| Concealed ducted | Premium renovation with planned bulkhead | Discreet grilles; highest building-work cost |
| Portable unit | Temporary use or rental | No fixed install; noisy and inefficient through a hose |
The supply air should travel along the room and mix before reaching occupied seating. A powerful unit blowing directly at a sofa feels uncomfortable even when the average temperature is right. Low-wall consoles can be excellent, but keep curtains, furniture and plants clear of the intake and discharge.
Installed cost in 2026
Allow roughly £1,800–£3,500+ for a good fixed single-split conservatory installation. A smaller high-wall system with short pipes and easy outdoor access sits near the lower end. Larger 5–7kW equipment, low-wall designer units, pumps, long concealed routes, electrical upgrades or difficult access push upward.
That price should state the exact indoor and outdoor models, capacity, standard pipe length, extra pipe rate, bracket or base, condensate route, electrical supply, trunking, commissioning, warranty, access and VAT. Compare it against the national UK installation cost guide.
Cooling and shading work together
Current UK guidance on cooling buildings treats solar control and blinds as part of overheating reduction. In practice, stop as much sun as possible before it becomes indoor heat: external shading is strongest, while suitable roof blinds and solar-control measures can still materially reduce the peak load.
During hot weather, close shading before direct sun reaches the glass. Keep the conservatory separated from the main house while it cools down, then use the connecting doors deliberately. Opening every window while the air conditioner runs makes the system cool a continuous stream of outdoor air.
On cooler nights, natural purge ventilation may do the work without the compressor. A sensible control routine uses passive cooling when outside is cooler, then a closed room and inverter cooling during hot periods.
Winter heating: useful, with one condition
Most fixed split units are reversible air-to-air heat pumps. They can warm a conservatory far more effectively than waiting for a distant radiator, and direct warm air suits occasional use. But the system must be sized for winter heat loss as well as summer solar gain.
A poorly insulated polycarbonate roof may make heating expensive even with an efficient heat pump. Improving the envelope can reduce drafts, shorten run time and keep temperatures stable after the unit turns down. Ask the designer for both heating and cooling outputs at relevant outdoor conditions.
Drainage, noise and the outdoor unit
Cooling removes water from humid air. A gravity drain with continuous fall is simple; a pump adds noise and maintenance, so use one only where the route needs it. Confirm where water discharges and that it cannot stain paving or create a slip hazard.
Place the condenser where it has unrestricted airflow, can be serviced and will not blow hot air into an enclosed alley. Consider your neighbours’ open windows and evening use. A correctly selected inverter that runs steadily is generally kinder than an oversized system cycling hard.
Planning and installer checks
Many house installations may fall under permitted development when the conditions are met, but the outdoor condenser remains an external alteration. Flats, listed buildings, conservation areas, leasehold restrictions and prominent locations need specific checks. Use our planning permission guide and obtain written freeholder consent where relevant.
Anyone installing or commissioning the refrigerant circuit needs the correct F-Gas qualifications. The survey should also confirm electrical supply, safe drilling, roof or glazing interfaces, drain route and service access.
What to ask before signing
What peak solar and winter loads were calculated? Which glazing and orientation were assumed? What capacity does the selected unit deliver at design conditions? What is the indoor night-mode sound level? Can the room be separated from the house? Where do refrigerant pipes, trunking and condensate go? Is a pump required? What shading improvement would allow a smaller system? Who handles planning or freeholder checks?
A quote that answers those questions is a conservatory design. A quote based only on floor area is an equipment guess.
Conservatory air conditioning FAQs
How much does conservatory air conditioning cost?
A fixed split system commonly costs about £1,800–£3,500+ supplied and installed for one UK conservatory. Larger 5–7kW systems, long pipe runs, pumps, premium low-wall units, difficult access and electrical upgrades can move the price higher. Because glass loads vary sharply, a survey and heat-load calculation are essential.
What size air conditioner does a conservatory need?
There is no reliable floor-area-only answer. The calculation must account for roof and wall glazing, orientation, glass specification, blinds or solar-control treatment, open connections to the house, occupancy and desired indoor temperature. A 20m² shaded modern orangery and a 20m² south-facing polycarbonate conservatory can need very different capacities.
What type of air conditioning is best for a conservatory?
A fixed inverter split is normally the strongest option: efficient, quiet and able to heat in winter. A low-wall console fits below glazing or a dwarf wall; a high-wall unit suits a solid house wall; a ceiling cassette or concealed unit may fit a large orangery with a suitable void. Portable units are noisy and lose efficiency through their window hose.
Can air conditioning heat a conservatory in winter?
Yes. Most modern splits are reversible air-to-air heat pumps. They can heat efficiently, but conservatories also lose heat rapidly through glazing, so the winter heat-loss calculation matters. Roof insulation, draught reduction and blinds can cut both heating and cooling demand.
Where should the indoor unit go in a conservatory?
On a solid wall or dwarf wall where supply air can travel across the space without blasting seats. Low-wall consoles are useful when high wall area is all glass; high-wall units may sit on the original house wall. The outdoor unit needs airflow, drainage, service access and a location considerate of neighbours.
Will a portable air conditioner cool a conservatory?
It may take the edge off a small, shaded space, but a single-hose portable exhausts hot air through a window and pulls replacement warm air back into the building. In a highly glazed south-facing conservatory it often runs loudly without holding setpoint. It is a temporary or rental solution, not equivalent to a correctly sized split.
Do I need planning permission for conservatory air conditioning?
The relevant external change is usually the condenser, not the indoor unit. Many houses can use permitted development subject to conditions, but flats, listed buildings, conservation areas and unusual placements need checks. Freeholder or landlord consent may also apply.
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