Every figure checked against its source on 7 November 2026
Air conditioning with no outdoor unit: how monoblocs work
Yes, you can have air conditioning without an outdoor unit. A monobloc keeps the whole machine indoors and breathes through two round grilles in the outside wall. It is the answer for a Dartford flat whose block has used its one permitted outdoor unit, or whose freeholder refuses anything on the elevation, at a cost in capacity and efficiency.
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How does a unit with no outdoor box get rid of the heat?
Through the wall. Instead of an outdoor condenser, the monobloc has two ducts of about 162 mm through the external wall, one drawing outside air in, the other blowing it out warmed. The compressor, both coils and the fans sit in one case on the inside wall. From the street all that shows is two round grilles.
Source: Unico Air specification.
What do you give up?
Capacity and a little efficiency. One well-known monobloc is rated at 1.80kW of cooling with a sound level of 27 to 38 dB(A) at a metre, enough for a bedroom or a small living room, not for an open-plan flat with a west-facing glass wall. A retailer's comparison puts the monobloc range at roughly 1.7 to 3.5kW of cooling and notes that a split system still offers a wider capacity range and marginally higher peak efficiency. The compressor is in the room with you too, so it is louder than the indoor unit of a split, though quieter than a portable. Sources: Unico Air specification; Quality Heating.
When does a flat need one?
In three situations. When the block has already used the single outdoor unit that permitted development allows and a planning application is not worth the wait. When the freeholder or management company will not allow anything on the elevation, which is common in newer blocks with managed facades. And when there is no safe outdoor position at all, as on a top-floor flat with no balcony and no flat roof. Dartford has 9,762 households in purpose-built flats and 812 in converted houses, and a fair share of our monobloc work is in them. Sources: Planning Portal; Census 2021.
Does it still need the freeholder's consent?
Yes. Two holes through an external wall alter the structure and the outside of the building, which the lease almost always reserves to the freeholder, so a licence to alter is still needed, and the grilles still count as an alteration to the elevation for planning if the building is listed or in a conservation area. The paperwork is lighter than for an outdoor unit, not absent. Sources: LEASE; Listed Buildings Act, section 7.
Does a monobloc heat as well?
The heat pump versions do. The same case runs in reverse in winter, with a heating output close to its cooling output, so an electric-only flat gets cheaper warmth from the same box. Running costs follow the same arithmetic as any heat pump: the cost guide has the current figures, and our air conditioning in Dartford page explains the housing behind the demand. Source: Unico Air specification.
Questions people ask
Is it the same as a portable?
No. A portable vents through a hose out of a window and runs hot and loud; a monobloc is fixed, sealed to the wall and far more effective. See portable against fixed.
Can the grilles go on a wall facing the road?
On an ordinary house, yes, since they are not an outdoor unit. In a conservation area or on a listed building the elevation matters, so ask first.
How much does one cost?
Checkatrade gives no monobloc figure, so it comes from a survey. Expect the unit to cost more than an equivalent split and the installation to cost less.
Sources we checked
- Puravent: Unico Air monobloc specification sheet
- Quality Heating: how monobloc air conditioners compare with splits
- Planning Portal: when an air source heat pump on a house or flats is permitted development
- Census 2021: accommodation type, Dartford
- LEASE: whether a leaseholder needs the landlord's permission to alter a flat
- legislation.gov.uk: section 7 of the Listed Buildings Act 1990
Worth knowing before you ring
With these we can usually tell you on the first call whether the job is simple.
- The postcode
- Whether it is a house, a flat or business premises, and roughly its age
- If you rent or lease, who owns the external wall
- Which room, how big, and the direction its window faces
- Any management company, conservation area or listing that applies
Decided? Our air conditioning in Dartford page covers what we install, what we maintain and where we go.
The services this guide leads to
Home air conditioning
The back bedroom, the new flat with the glass wall, the loft nobody can sleep in: cooled in summer, warmed in winter.
Air conditioning installation
The whole job from the first measurement to the handover of the remote, with every consent checked on the way.
Air-to-air heat pumps
The same wall unit, run the other way: a room heated for pence an hour, with the summer cooling thrown in.
Other guides
What does air conditioning cost to fit and to run?
Where the money goes: the unit, the labour, the wiring, the electricity, and the extras a flat or a new estate brings.
Air conditioning and planning permission: the rules for England
Every permitted development condition in one table, then the twists Dartford's new estates and conservation areas add.
Air conditioning in a flat: who has to agree, and in what order
Lease, freeholder, management company and planning, in the order to tackle them.
Bedroom air conditioning: what it does for sleep, and what it costs
The sleep threshold, noise at night, sizing and the price of a quiet bedroom.
Cooling a loft conversion: the options that work
Why lofts cook, the free fixes first, then where a unit goes on a dormer.
What size of air conditioner does a room need?
Kilowatts and BTU by room size, with the adjustments that matter.
How to check an air conditioning installer on the F-gas register
The company certificate, the engineer's category and where to look them up.
Portable or fixed air conditioning: which is right for you?
Price, power, noise and running cost, and when a portable is the right call.
Want us to ring you?
A name, a number and a postcode is enough. Say which room if you can. Or ring 01322 952910.