Find a cool apartment: What to check when searching for a home during a hot summer

Why heat protection matters more when choosing a home

The Climate CH2025 scenarios expect more frequent and intense heat events. In a world that is 3°C warmer globally, Switzerland’s hottest day of the year would be around 4.4°C warmer on average than in 1991–2020; Zurich is expected to experience about five times as many tropical nights.^[1]

The summer of 2025 was among Switzerland’s warmest since measurements began in 1864, with significant heat in June and August. Long-term climate trends make summer comfort increasingly relevant when choosing a home.^[2]

Heat is not merely a comfort issue: 410 deaths in Switzerland between May and September 2025 were attributed to heat. Older people, people with chronic illnesses, pregnant women, babies and young children are particularly vulnerable.^[3]

For a home that may be occupied for years, summer heat protection therefore belongs alongside rent, location, noise and layout as a core quality criterion.

Key overheating risks at a glance

Top floor, middle floor or ground floor?

A top-floor apartment is not automatically too hot. The roof build-up, insulation, glazing, shading and ventilation are decisive. Without good heat protection, however, the upper floor can store heat throughout the day and release it well into the night.

Roof windows are particularly critical because they can admit more heat than vertical windows. Check for external roller shutters or heat-protection awnings and make sure they work fully.^[4]

Middle floors often benefit from apartments above and below. Ground-floor homes may be cooler, but security, moisture, privacy and the ability to keep windows open at night must also be assessed.

Assess orientation and window area

The simple rule that south is hot and north is cool is incomplete. East- and west-facing windows can cause serious overheating because the summer sun is low in the morning and evening. South-facing glazing may be easier to shade with overhangs or horizontal devices.^[4]

Large windows provide daylight but also solar heat. In new buildings, ask about the glazing’s solar-energy transmittance and the summer heat-protection concept. In existing homes, the actual performance of blinds and surrounding shade is more important than a single technical value.

North-facing or well-shaded east-facing bedrooms are often favourable. West-facing bedrooms receive heat late in the day, precisely when the room should begin cooling for the night.

External shading matters more than attractive curtains

The most effective shading blocks radiation before it reaches the glass. External venetian blinds, shutters, roller shutters, awnings and structural shade are therefore substantially more effective than curtains and internal blinds.

Test every blind. Look for damaged slats, blocked motors, wind sensors that retract too readily and whether a balcony or overhang actually shades the window during the crucial hours.

Curtains improve glare and privacy, but once sunlight has passed through the glass, much of its energy is already indoors. They are an addition, not an equivalent replacement for external shading.

Check cross-ventilation and night cooling

Night cooling removes heat stored in walls and ceilings. Several hours of cross-ventilation through large, opposing windows is especially effective; outdoor air is usually coolest before sunrise.^[4]

Do not merely count the windows. Check whether air can genuinely flow through the home. Are openings available on two sides? Can internal doors be secured? Is there a small secure ventilation panel for overnight use?

Traffic, railway lines, restaurants, insects and burglary risk can make theoretical ventilation unusable in practice. Stand quietly for several minutes with the windows open.

Insulation, thermal mass and building services

Massive walls, ceilings and floors can absorb heat during the day and release it during the cooler night. This thermal mass works best when it is not completely separated from the room by suspended ceilings or thick coverings.

Good insulation slows heat entering through the roof and façade. A highly insulated new building can still overheat when extensive glazing, poor shading, internal heat gains and insufficient night cooling coincide.

For mechanical ventilation, ask about the summer bypass, airflow, controls and night mode. Comfort ventilation is not automatically air conditioning and may not actively cool an already hot room.

Positive features include geocooling or a reversible heat pump, provided the system is properly designed and actually available to the apartment.

Urban climate, trees, courtyards and sealed surfaces

Cities heat up strongly during the day and cool more slowly at night than surrounding areas. Trees, green areas, air corridors, elevation, dense development and sealed surfaces can create noticeable differences within the same city.

A home above a large asphalt area, in a narrow street canyon or opposite a sun-heated dark façade may receive more stored and reflected heat at night than a similar home beside a green courtyard.

Trees provide effective shade, but also consider daylight, pollen and whether they are likely to remain. A young tree shown in a development brochure may provide little shade for years.

How to test the apartment during the viewing

1. Where possible, arrange a second viewing on a sunny, warm day between roughly 4 and 7 p.m.
2. After a few minutes, measure living-room and bedroom temperatures with your own thermometer, away from windows, external walls and direct sun.
3. Compare indoor and outdoor temperatures and notice whether the apartment keeps heating despite closed windows.
4. Operate every blind, window and ventilation panel and test their condition and the resulting airflow.
5. Carefully feel roof slopes, ceilings and sun-exposed internal surfaces; strong radiant heat is a warning sign.
6. Keep the windows open and assess traffic, night noise, smells and security.
7. Ask the current tenant separately about typical July and August peaks and whether sleeping was possible at night.
8. Photograph or note orientation, shade, window positions and cooling equipment for later comparison.

Cool-home check: estimate the overheating risk

Questions to ask

• How hot do the living room and bedrooms become during several consecutive hot days?
• What temperatures remain at around 2 or 5 a.m.?
• Have there been complaints, measurement records or requests for heat-protection measures?
• Are all external blinds part of the rented property, and will the manager repair defects?
• Can the home be cross-ventilated, and is this realistic at night given noise and security?
• How is the roof insulated, and when were the roof and windows last refurbished?
• Does the ventilation system have a summer bypass or active cooling?
• Can the heat pump cool through the floor or ceiling system?
• Are portable air conditioners permitted, and where may the exhaust hose be routed?
• Would a permanently installed split unit be acceptable in principle?
• What electricity and ancillary costs resulted from summer cooling?
• Will trees, awnings or other shading elements be removed or altered?

Typical apartments compared

An excessively hot rental home: the legal position

Swiss tenancy law does not specify a universally applicable summer maximum for homes. Under Article 256 CO, however, the landlord must provide and maintain the property in a condition fit for its intended use. Defects not caused by the tenant may trigger rights under Articles 259a et seq. CO, depending on their severity.^[6]

A home is not defective merely because it becomes warm on isolated exceptionally hot days. Substantial, persistent overheating that is unusual relative to outdoor conditions may nevertheless constitute a defect in an individual case. The degree of impairment, building condition and reasonable behaviour by the tenant are relevant.

Record the room, time, indoor and outdoor temperatures, ventilation and shading over several days. Notify the landlord in writing and request consideration of proportionate measures such as external blinds, shutters or heat-protection film.

There is no automatic right to air conditioning. A rent reduction is also not automatic and depends on the existence and severity of a defect, notification and the individual circumstances. Obtain advice before withholding rent or making structural alterations.

Air conditioning, heat pumps and fans

Fans do not lower room temperature, but moving air improves perceived comfort and generally uses much less electricity than portable air conditioners.

Portable monoblock units require no permanent façade installation but are often noisy and inefficient because warm outside air is drawn in to replace exhausted air. Condensate, window sealing and neighbour noise matter.

A fixed split system in a rented home normally requires the landlord’s written consent. Façade alterations, noise, refrigerants and cantonal or municipal permissions may also be relevant.

A reversible heat pump or geocooling may be more efficient. Ask about the achievable temperature reduction, operating costs and individual control.

What helps after moving in

• Close external blinds early, before direct sunlight reaches the glass.
• Keep windows closed during the day whenever outside air is warmer than indoor air.
• Cross-ventilate for as long as possible at night and early in the morning.
• Reduce heat from ovens, powerful computers, lighting and other appliances.
• Use quiet fans in occupied and sleeping areas.
• Document temperatures during heat periods if the home overheats despite correct behaviour.
• Protect vulnerable people and act quickly if signs of heat stress appear.^[5]

Common home-search mistakes

1. Viewing only on a cool morning.
2. Rejecting every top-floor home or assuming every modern new build is cool.
3. Looking only at orientation while ignoring glazing area and shading.
4. Treating curtains as equivalent to external shading.
5. Assuming comfort ventilation is air conditioning.
6. Assuming cross-ventilation without testing window positions, noise and security.
7. Accepting “it gets a little warm” without asking for actual temperatures.
8. Failing to document promised cooling functions in the lease or property description.
9. Demanding a rent reduction immediately without measurements and written notification.
10. Installing a split unit without written consent and permission checks.

Checklist for a cooler apartment

Sources and information date

1. NCCS: Climate CH2025
2. MeteoSwiss: Climate change particularly pronounced in Switzerland
3. NCCS: Heat-related deaths through 2025
4. SwissEnergy: Protecting buildings from summer overheating
5. Federal Office of Public Health: Protecting yourself in hot weather
6. Swiss Code of Obligations: Articles 256 and 259a et seq.
7. Zurich courts: Defects in rented property
8. Swiss Tenants’ Association: When a home is too hot

Updated: 3 August 2026.

Frequently asked questions about finding a cool apartment

Summary

No single feature guarantees a cool apartment. The interaction of floor, roof, glazing, orientation, external shading, thermal mass, insulation, cross-ventilation, surroundings and building technology is decisive. View the property on a warm late afternoon, measure temperatures, test windows and blinds and record important assurances in writing. Checking these points before applying reduces the risk of discovering a summer heat trap only after moving in.