A growing problem across Europe — and how different countries are handling it
You have seen it. Everyone who cares about historic buildings has seen it.
A carefully restored 19th century facade. Original stonework, period ironwork, authentic render — everything considered, everything right. And then, screwed directly into the facade at first floor level, a white plastic box the size of a suitcase, with a grille, a drainpipe, and a power cable running down the wall in a loose loop.
The air conditioning unit. The uninvited guest on the historic facade.
It is not going away. As European summers become hotter and the expectation of interior cooling becomes standard rather than exceptional, the pressure to install air conditioning in historic buildings is increasing every year. The question is not whether it will happen, but how — and whether the buildings that have survived a century or more will be allowed to survive it with their character intact.
Why this matters more than it looks
An air conditioning unit on a historic facade is not just an aesthetic problem, although it is certainly that. It is also a practical one.
The fixings penetrate the facade. On historic render, brick, or stone, those penetrations create entry points for moisture. The drainpipe — which discharges condensate water — directs a constant flow of water onto the wall surface below it, often directly onto stonework or render that was never designed to receive that load. The unit itself creates localised heat and vibration that can affect the surrounding fabric over time.
And the cables. The cables that always seem to find the most visible possible route down the most significant part of the facade.
On my last restoration they made big ugly holes thru some beautyfull glazed bricks—luckily, I had some lying around that were the perfect color! But that was a real coincidence! People who install AC units don’t pay attention to historic facades.
France — the strictest approach
France has developed the most systematic approach to air conditioning on historic and protected buildings of any country in Europe, and it is worth understanding in some detail.
In areas subject to the oversight of the Architecte des Bâtiments de France — which covers a significant proportion of French historic city centres — any installation visible from the public realm requires authorisation. In practice, this means that units on streetfacing facades are almost universally refused in protected zones. Owners are expected to find solutions that are not visible from the street: rear facades, internal courtyards, or alternative cooling systems.
The enforcement is not perfect, and there are plenty of French historic buildings with visible units — particularly in areas where oversight is less rigorous. But the principle is clear, and in the most significant historic centres, it is applied consistently.
The UK — listed building consent
In England, Wales, and Scotland, installing an air conditioning unit on a listed building requires Listed Building Consent in addition to any planning permission that might be needed. The test applied is whether the installation would affect the character of the listed building — and a visible unit on a significant facade will almost always fail that test.
Historic England has published guidance on mechanical services in historic buildings that makes the position clear: the installation of services should be reversible, should not damage historic fabric, and should not be visible in a way that harms the character of the building.
In practice, many listed building owners find creative solutions — units concealed behind period-appropriate screens, installations on less significant parts of the building, or alternative cooling systems that avoid the external unit entirely.
Belgium — a patchwork of approaches
Belgium’s approach to air conditioning on historic buildings reflects its broader heritage governance structure: divided by region, variable in practice, and dependent heavily on whether a building is formally protected.
For buildings within a’ “beschermd stadsgezicht” or with individual protection status, the rules are broadly similar to those in France and the UK — visible units on significant facades require permission and are routinely refused.
For the much larger stock of historic buildings that have heritage value but no formal protection, the situation is less clear. Municipal planning regulations apply, but enforcement varies considerably between communes. The result is the familiar patchwork: some streets in historic centres where units are carefully managed, others where they proliferate without apparent constraint.
Italy — the gap between law and practice
Italy presents the paradox that characterises its approach to heritage more broadly. The formal legal framework is comprehensive — installations on historically significant buildings in protected zones require approval from the Soprintendenza, and visible units on significant facades are subject to the same controls as any other alteration to protected fabric.
The gap between the law and what actually happens on Italian streets is, however, significant. In many historic centres, air conditioning units have proliferated on facades that are formally protected, with a combination of unauthorised installations, retroactive approvals, and selective enforcement producing results that are far from what the legislation intends.
Rome is perhaps the most dramatic example — a city where extraordinary historic facades coexist with a density of visible air conditioning units that would be unacceptable in most northern European historic centres.
Switzerland — the predictable exception
Switzerland applies its characteristic precision to this problem as to most others. In the historic centres of cities like Bern, Basel, and Zurich, visible air conditioning units on street-facing facades are effectively prohibited in practice, even where formal protection does not apply. The combination of strict cantonal building regulations, active enforcement, and a cultural attitude that makes visible technical installations on historic buildings broadly unacceptable produces results that are visible — or rather, invisible — on the streets.
The alternatives — what responsible installation looks like
The argument that air conditioning is incompatible with historic buildings is not sustainable. The need for cooling is real, and the alternative to a thoughtfully installed system is often an improperly installed one. The question is not whether to cool the building, but how.
Rear and courtyard installations are the most straightforward solution where the building layout permits. A unit that is not visible from the street causes far less harm than one that is, even if the installation itself is otherwise identical.
Concealed installations — units placed behind screens, within existing architectural features, or in locations that are technically accessible but not visually prominent — require more thought and sometimes more expense, but are achievable on most buildings.
Alternative cooling systems — underfloor cooling, chilled beam systems, and other approaches that do not require an external condensing unit — are increasingly available and increasingly affordable. For significant historic buildings, the additional cost of an appropriate system is almost always justified by the reduced impact on the fabric.
The drainpipe problem deserves specific attention. Whatever the unit location, the condensate drain must be directed to an appropriate discharge point — not onto the historic wall surface. This sounds obvious. It is remarkably often ignored.
A question to the Guild — and to owners
Have you encountered air conditioning installations on historic buildings that were done well — that found a solution which served the occupant’s needs without compromising the facade?
And for property owners: if you are considering air conditioning in a historic building, please ask the question before the fixings go in. The penetration that damages a carved stone surround, the drainpipe that stains a century of carefully maintained render — these are not reversible. The conversation with a craftsperson or a heritage advisor costs nothing compared to the damage that a poorly considered installation can cause.
The building kept you cool for a century through thick walls and good design. It deserves a little more thought before you drill into it.
RestoreFacade Guild — for the craftspeople and owners who think before they fix.