Heatwave in Switzerland: can you claim a rent reduction?

Every summer the same question comes back with the heat: if your flat turns into an oven, can you pay less rent? The short answer: sometimes yes, but it is neither automatic nor unconditional. This guide explains when heat becomes a defect under Swiss tenancy law and how to respond correctly.

At a glance

• Excessive heat can constitute a defect in the leased property (Art. 259d of the Code of Obligations) and open the right to a rent reduction. But it is not automatic.
• Unlike heating in winter, there is no legal maximum temperature for summer. Everything is assessed case by case.
• It is easier to establish in a newer building (where good insulation is expected) than in an older one.
• You cannot reduce your rent unilaterally: you must notify the defect in writing, pay under reservation, and then go through the conciliation authority if there is a dispute.
• The tenant association notes that you can pursue two things: a rent reduction and/or measures to make the property liveable (blinds, sun protection).

What you need to understand

Under Swiss law, a tenant has the right to a property that corresponds to the agreed use. If a defect reduces that use, Art. 259d of the Code of Obligations allows a claim for a proportional rent reduction for as long as the defect persists.

The nuance with heat: there is no statutory threshold for summer. In winter, the heating is expected to maintain a comfortable temperature (often cited around 20 to 21 °C in living rooms); a failure there is a fairly clear defect. In summer it is more subtle, because part of the heat comes from outside and does not depend on the landlord.

When heat can be a defect

It all depends on the source and scale of the problem:

• More likely to be recognised as a defect: a property that overheats because of its characteristics (large glazed surfaces without sun shading, poorly insulated top floor, no possibility of ventilation), with temperatures clearly and durably above normal. The Federal Tribunal has already recognised a defect in a case of excessive heat and brightness caused by large glass panels without blinds.
• In a newer building: the standard is higher. A temperature that stays 3 to 5 °C above normal for an extended period may justify a reduction.
• In an older building: considerably harder. You cannot expect the same thermal insulation from an old building as from a new one.
• Less likely to be recognised: an exceptional and general heatwave that affects everyone and that the landlord could not have avoided, where there is no specific defect in the property itself.

In short: it is the abnormal heat linked to the property that matters, not the heatwave in itself.

What to do

The procedure is precise. Do not skip any step, or you risk losing your rights:

1. Document everything. Record the temperature at different times of day (photos of the thermometer, dates, duration), note the impossibility of ventilating or the absence of blinds.
2. Notify the defect in writing to the management or the landlord (notice of defect), requesting measures within a reasonable time. Keep a copy.
3. Pay your rent "under reservation". State this in writing: this is what preserves your right to a retroactive reduction. Never stop paying.
4. Request a reduction proportional to the inconvenience, and/or modifications (blinds, sun protection).
5. If no agreement is reached, refer the matter to the conciliation authority for tenancy disputes (free of charge). This is the mandatory step before any court.

How much of a reduction to expect

There is no official scale. The reduction is proportional to the loss of use: the stronger and longer the inconvenience, the higher it is. In practice, for seasonal overheating limited to a few rooms, the reductions accepted are often modest and limited to the period in question. The conciliation authority helps to find a reasonable amount.

Common mistakes

• Reducing your rent yourself without notifying anyone. That is the surest way to put yourself in the wrong, or even in default of payment.
• Forgetting the "under reservation" notation: without it, no retroactive reduction.
• Not documenting: without evidence of temperature and duration, the defect is difficult to establish.
• Believing a legal threshold exists for summer: it does not - everything is assessed case by case.
• Confusing a general heatwave with a defect in the property: only what is attributable to the property itself is legally defensible.

Where to find official information

• Code of Obligations · Art. 259a to 259d (defects and rent reduction)
• hausinfo.ch · Excessive heat in a rental flat
• Ville de Geneve · Maximum temperature of a dwelling in summer
• Your cantonal tenant association (ASLOCA) - legal advice and template letters.

How Admini can help

Making a defect claim is first and foremost a matter of evidence and letters sent at the right time:

• Centralise your lease, your defect notices and your correspondence with the management in one place.
• Keep your evidence to hand: temperature photos, dates, duration of the overheating.
• Find your lease or a letter in seconds when you are putting your file together.
• Prepare a clear dossier to hand over to your cantonal tenant association or the conciliation authority.

The aim is not to replace legal advice, but to give you the means to act quickly and effectively when your home becomes unliveable.