AC in an Altbau or Listed Building: What Renters Are Allowed to Do

Old buildings and heritage protection change the rules for cooling. Here is what you can install without permission, and where the façade is off-limits.

6 min read · Updated July 2026

An Altbau with stucco ceilings, tall windows and a handsome façade is a joy to live in, right up until the first real heat wave. Once you want to cool it down, two questions come up fast: am I even allowed to install AC here, and does anything change if the building is listed (denkmalgeschützt)? The short answer is that you have a lot of freedom indoors and almost none on the façade. This guide walks through what works without permission and where you should ask first.

Altbau vs. listed building: what actually changes

"Altbau" is not a legal category on its own. It usually just means a pre-war building, but in practice it often comes bundled with things that matter for AC: a landlord who cares about the look of the house, local conservation rules (Milieuschutz or an Erhaltungssatzung), and sometimes heritage protection. Denkmalschutz is the strict one. It is regulated at state level (for example the DSchG Bln in Berlin and the BbgDSchG in Brandenburg), and as a rule everything that is part of the protected substance is covered.

• Not listed, just old: the main constraint is your landlord and any local façade rules. Anything you screw or drill into the building needs consent.
• Listed (denkmalgeschützt): the protected fabric is off-limits without a heritage permit. That almost always includes the façade, historic windows, and often visible roof surfaces.
• Near a monument: even a non-listed building can be caught by "Umgebungsschutz" if a visible change would affect a protected neighbour.

What you can use without any permission

The good news for renters is that the most common cooling options do not touch the building at all, so they sit outside both landlord consent and heritage rules. They cool the room without changing any protected substance.

• Mobile monobloc units: a single free-standing device with one exhaust hose. The hose vents through a tilted or slightly opened window, no drilling, no fixed fitting.
• Permanently sealed mobile split units: two connected parts with a hermetically sealed, pre-filled refrigerant circuit. Because the circuit is closed, no F-Gas certified technician is needed and you can set it up yourself.
• Window units: rare in Germany and often awkward in Altbau casement windows, but where they fit without permanent structural change they follow the same logic.

Where the façade becomes the problem: fixed split systems

A classic fixed split system is a different story. It has an outdoor condenser that has to be mounted on the wall or balcony, connected through a core-drilled hole to the indoor unit. That combination triggers almost every rule at once.

• Structural change (bauliche Veränderung): mounting a unit and drilling through the wall alters the building, so you need the landlord's written consent as a renter.
• Refrigerant handling: filling and connecting the refrigerant circuit falls under the EU F-Gas Regulation and must be done by a certified company, not by you.
• Building and conservation law: depending on the state and the location, a fixed installation can need a building permit, and on a protected façade the outdoor unit is frequently refused outright.

Denkmalschutz in practice: façade, windows, permits

In a listed building the deciding question is whether a change touches the protected substance and whether it is visible. Anything on the outside usually is. An outdoor unit, a wall penetration, or a permanently fitted window kit visible from the street will typically need a heritage permit (denkmalrechtliche Erlaubnis) from the lower heritage authority (Untere Denkmalschutzbehörde), and permission is far from guaranteed.

Interiors can be protected too, if stucco, historic doors or original windows count as part of the monument. A free-standing mobile device changes none of that and stays unproblematic. A core drilling to the outside or a fixed built-in does the opposite. If you are unsure, a short call to the local heritage authority before you buy anything saves a lot of trouble, and if you own rather than rent, you still need that permit for façade work.

If you rent in an old building: a simple path

You do not need to fight your way through building law to stay cool. Most renters in an Altbau are best served by a device that never touches the façade in the first place.

• Start with a mobile monobloc or a sealed mobile split. No consent, no permit, no certified installer.
• Use a proper window seal for the hose instead of drilling. It is removable and leaves no trace.
• Keep noise and condensate in mind so you do not create a separate nuisance issue with neighbours.
• Only consider a fixed split system if you own the flat or have written landlord consent, and check heritage and permit requirements before ordering.

So the honest summary for an Altbau, listed or not: cool the room, not the wall. A mobile monobloc or a sealed mobile split gets you through the summer with no permit and no certified installer, and it never touches the protected façade. Seasonal rental options like the ones KlimaLegal offers are built around exactly that constraint, so you keep the comfort and leave the building untouched. Save the paperwork for the day you actually own the wall you want to drill.

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