Facts and figures last checked on 9 November 2026
No outdoor unit? Monoblocs, portables and splits compared
Yes, it can be done. A through-wall monobloc keeps every working part indoors and shows only two round grilles outside, which suits Ilford flats where the freeholder will not accept an outdoor box. It gives up some output and efficiency to a split, and avoids a portable's hose hung out of an open window. Here is how the three compare.
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How does air conditioning work with no outdoor unit?
The outdoor half moves inside. A monobloc holds the compressor, both heat exchangers and the fans in one cabinet fixed to the inside face of an outside wall, and it breathes through two ducts cored straight through that wall: one draws outdoor air in, the other sends it back out carrying the room's heat. On the Unico Air those holes are 162 mm across. In winter the heat pump versions run the cycle the other way and bring warmth in.
Source: Unico Air data sheet.
How does a monobloc compare with a portable and a split?
| Through-wall monobloc | Portable | Split | |
|---|---|---|---|
| Where the machinery is | All in one cabinet on the inside wall | All in one box on the floor | Compressor outside; fan and coil inside |
| What shows outside | Two round grilles | A hose through a part-open window | An outdoor unit and a pipe run |
| Cooling output | 1.73 to 3.50 kW across one retailer's range; the Unico Air is 1.80 kW | Sold by BTU; Checkatrade prices a 12,000 BTU model | 2.5 kW for a typical bedroom model, with larger sizes available |
| Seasonal efficiency | SEER up to 5.10 and SCOP up to 3.80 on that range | No like-for-like figure in our sources | SEER 7.4 to 10.5 and SCOP 4.1 to 5.2 on three 2.5 kW models |
| Sound in the room | Unico Air: 27 to 38 dB(A), measured 1 metre away | Compressor in the room; no comparable figure | 19 to 20 dB(A) on the quietest fan setting, 40 to 42 at full speed |
| Fixed to the building | Yes, through two cored holes | No | Yes, and it uses the property's permitted outdoor unit |
| Price guide | No published figure; priced at survey | £300 to £420 for 12,000 BTU (Checkatrade) | About £1,900 unit and labour, our sum of Checkatrade's figures, plus wiring |
Sources: Unico Air data sheet; Quality Heating; Checkatrade; Mitsubishi Electric; Daikin; Fujitsu; Planning Portal.
What does a monobloc give up?
Some output, some efficiency and some quiet. Quality Heating, which sells monoblocs, concedes that a split can cover more sizes and edge ahead on peak efficiency, and the published seasonal figures agree: SCOP up to 3.80 on its monobloc range against 4.1 to 5.2 on the three splits in the table. With the compressor in the room, the quietest monobloc figure we found, 27 dB(A), is above a split indoor unit's lowest setting of 19 to 20 dB(A). For a bedroom or a modest living room that is often a fair trade; where a whole open-plan flat faces west through big windows, the output may fall short. Sources: Quality Heating; Unico Air data sheet; Mitsubishi Electric; Daikin; Fujitsu.
Who is a monobloc for?
Mainly people who cannot get an outdoor unit agreed, and in Ilford that is a large group: purpose-built flats are 25.36% of Redbridge households, flats in converted houses another 6.55%, and flats over shops or in commercial buildings 1.25%. Three situations point to one:
- The freeholder will not have an outdoor unit. Outside walls are normally parts the freeholder keeps, and for those they need not consent and may ask a premium. Two grilles are a smaller request than a box on a bracket, though still a request.
- The block's allowance is used up. Permitted development gives a block of flats one outdoor unit; once a neighbour has it, another needs planning permission.
- The only wall available is the wrong one. Inside a conservation area, outdoor units are kept off any road-facing wall or roof. Whether two grilles on that wall need an application is worth asking the council before anything is drilled. The planning guide sets out the rules for outdoor units.
Sources: Area Insights; LEASE; Planning Portal.
Does a monobloc still need the landlord's or freeholder's agreement?
Yes. Two holes through an outside wall are an alteration, so a lease that requires consent for alterations covers them. LEASE advises that a freeholder ought not to refuse unreasonably when the change improves the flat, though some leases ban alterations altogether. Tenants need the landlord's written yes first, and more Ilford households rent than a decade ago: Redbridge's private rented share went from 22.9% in 2011 to 30.45% in 2021. On a listed building, works affecting its character need listed building consent. Sources: LEASE; Redbridge Council, 2011; Area Insights, 2021; the 1990 Act, section 7.
Can a monobloc heat a room in winter?
The heat pump versions can. The Unico Air 8 HP is rated at 1.70 kW of heating against 1.80 kW of cooling, and Quality Heating's range reaches a SCOP of 3.80. On our sum, that seasonal rating turns each 26.32p kWh of electricity into about 3.8 kWh of warmth, roughly 6.9p per kWh of heat, where a plug-in heater turns the same 26.32p into a single kWh. The running costs guide sets this against splits and gas, and the rest of what we fit is on our Ilford air conditioning homepage. Sources: Unico Air data sheet; Quality Heating; Ofgem.
Common questions
Is a monobloc just a portable fixed to the wall?
No. A portable stands on the floor, and its exhaust hose needs a window left part open. A monobloc is sealed into two cored holes and draws and returns its air through them. New portables whose HFC refrigerant has a GWP above 150 are also banned from sale.
Will one suit a top-floor flat without a balcony?
Often, because nothing hangs outside and the ducts go straight through the wall. The wall still needs the freeholder's agreement, and finishing the grilles may need access from outside.
What does a monobloc cost?
Checkatrade publishes no figure for them, so the price comes from a survey of the wall and the room.
Sources for this page
- Puravent: the Unico Air through-wall unit, data sheet
- Quality Heating: through-wall monoblocs set against split systems
- Checkatrade: national figures for fitting air conditioning (May 2026)
- Mitsubishi Electric: data sheet for the MSZ-LN25VG2 and MUZ-LN25VG2 split, with power input, sound levels and refrigerant (June 2024, in French)
- Daikin: FTXM-R and RXM-R data sheet with sound levels and seasonal ratings (2021, published by the retailer Evomart)
- Fujitsu: specification for the ASYG KMCC wall units, with power input, seasonal ratings and indoor sound levels
- Planning Portal: permitted development for an air source heat pump on a house or a block of flats
- Area Insights: Redbridge house types and tenure, Census 2021
- Redbridge Council: housing and households at the 2011 Census (briefing)
- LEASE: what a freeholder may charge for giving consent
- LEASE: asking the freeholder before altering a leasehold flat
- legislation.gov.uk: when listed building consent is required (1990 Act, s.7)
- Ofgem: capped unit rates and standing charges for October to December 2026
- GOV.UK: the F gas bans on new equipment, with dates
Five things to have handy
Answers to these let us judge, before anyone visits, how involved the job will be.
- Your postcode
- The building: terrace, semi, detached, a flat in a block or over a shop, or business premises
- Whether you own it outright, hold a lease or rent it
- Which room it is, its rough size, and whether it gets the morning or the afternoon sun
- Anything that limits outside changes: a conservation area, a listing, a lease clause or a managing agent
Want to talk about your own home or premises? Our page on air conditioning in Ilford sets out what we fit, how we look after it and where we work.
Services related to this guide
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Planned from survey to switch-on: a wall-mounted split, with the route, the wiring, the consents and the neighbours' window worked out before we drill.
More guides
Air conditioning costs: fitting, wiring and the bills that follow
National figures for the unit, the labour and the wiring, then the extras a lease, a landlord or a conservation area can bring.
What air conditioning costs to run, worked out at today's price cap
Pence per hour and pounds per summer for a 2.5 kW split, with winter warmth set against a fan heater and mains gas.
Does air conditioning need planning permission? The rules and the exceptions
When a unit counts as permitted development, and where Redbridge, Havering, Waltham Forest, Hackney and Chigwell differ.
How loud is air conditioning? Indoor units, outdoor units and the neighbours
Makers' decibel figures, the 37 dB(A) sum at the neighbour's window, and what happens if someone complains.
Cooling a bedroom: sleep, quiet running and the right size of unit
Why bedrooms are the first room to cool, how quiet a unit runs on its lowest setting, and how big it needs to be.
Air conditioning in a loft conversion: heat, siting and pipe routes
The research on hot London lofts, what to try first, and how a unit and its pipes fit a dormer or a gable.
Sizing an air conditioner: kilowatts, BTU and the room in front of you
Two published sizing tables side by side, the conversion between them, and what changes the answer.
Checking the F-gas register before you hire an air conditioning firm
The firm's certificate, the engineer's own qualification, how to check both, and where R32 sits in the leak-check rules.
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