Air conditioning planning permission outside England

Every British article about air conditioning and planning permission is about England. This one is not, because three of the four UK nations run their own regime and the differences are not cosmetic.

The most important of them is Scotland’s, and it is not about size or siting at all. It is about what the machine is for.

Scotland: the condition is the use, not the box

In Scotland an air source heat pump on or within the curtilage of a dwelling sits in Class 6H of Part 1A of the schedule to the 1992 order.

The Scottish Government’s householder permitted development rights guidance sets out the conditions, and one of them restricts use to domestic heating or hot water.

Read that against what an air conditioner is bought for. A reversible unit heats, so it satisfies the condition when it is heating. What the condition does not obviously cover is running the same unit in cooling mode in July, which is the entire reason most people buy one.

England handles this from the other direction. There, the condition is that the unit is not solely used for the purpose of cooling, which a reversible unit passes comfortably whatever it does in August. Scotland’s wording is positive rather than negative: it says what the right is for, rather than what disqualifies you from it.

Nobody should read that as settled. It has not been litigated, local authorities will differ, and this is exactly the point at which a reader needs their own planning authority rather than a website. But anybody fitting a reversible unit in Scotland primarily for cooling should understand that the permitted development right they are relying on is framed around heating.

Three further Scottish conditions worth knowing:

• One unit. More than one air source heat pump on the same building or within its curtilage takes it outside the class.
• One metre of protrusion. No part may protrude more than 1 metre from the outer surface of an external wall, roof plane, roof ridge or chimney.
• Conservation areas. The unit must be at ground floor level and on the rear elevation.
• Listed buildings. Not permitted within the curtilage of one.

Scotland also retains a requirement to comply with MCS Planning Standards or equivalent. England removed its equivalent requirement on 29 May 2025. If you have read that MCS no longer matters for planning, that was an England article.

Wales: closest to England, with a sound test attached

Wales treats air conditioning the same way England does on the question that matters most. The Welsh Government’s guidance on planning permission for domestic heat pumps states that the unit cannot be one designed for the purpose of cooling only.

So the advice that applies in England applies here too, for the same reason: buy the reversible one and the planning problem disappears.

The Welsh conditions as published:

The MCS 020(a) condition is the one that catches installers rather than homeowners, and it is a real condition of the right rather than best practice. A unit that fails the sound assessment at a neighbour’s window is not permitted development in Wales however small it is and wherever it sits.

Northern Ireland: no roofs, and a height limit

Northern Ireland runs Class G of the 2015 order, amended by the Department for Infrastructure with effect from 4 July 2023. The amendment relaxed the position considerably: before it, the unit had to be 30 metres from any other dwellinghouse, which ruled out most of the housing stock.

The current position:

Two things stand out. The roof prohibition is absolute, where England distinguishes pitched from flat. And the condition on use, that it must provide heat within the curtilage, is phrased like Scotland’s rather than England’s.

What differs, in one table

The row that matters is the first one, and the row that surprises people is the last one. England’s deregulation in May 2025 was an England measure. It did not change anything in the other three nations, and a great deal of UK coverage published since then reads as though it did.

What to do with this

The honest answer in all four nations is the same: check with your own local planning authority before you order anything. Permitted development is a default, not a permission, and it can be removed locally by an Article 4 direction, by a condition on the original planning permission for the house, or by a leasehold or tenancy agreement that has nothing to do with planning law at all.

For England specifically, the Class G planning checker on this site walks through the conditions. It is England only and says so. The deeper England position, including the provision that decides most cases, is in the planning rule that decides what air conditioning you can fit.

And the choice that solves the most problems at once has not changed regardless of which nation you are in. A reversible unit is permitted development in England and Wales where a cooling-only unit is not, it sits better against the Scottish and Northern Irish conditions on use, and in England it is the version that attracts the Boiler Upgrade Scheme grant. A cooling-only box has nothing going for it except a slightly shorter spec sheet.