01
+4.4 °C
possible increase in hottest-day temperature
in a world 3 °C warmer than 1991–2020
Property news and apartment search · Hot summers
Finding a cool apartment: What to look for when searching for a home during a hot summer
An attic apartment, large west-facing windows and no external blinds can turn a bright dream home into a heat trap in summer. This guide explains how to spot overheating risks in property listings and viewings, which questions to ask, and what rights you may have if a rented apartment in Switzerland remains excessively hot.
Author: Nikita von Niederhäuser, UrbanHome property expert Updated: · Reading time: approx. 18 minutes
02
5×
more tropical nights
for Zurich under the corresponding climate scenario
03
410
heat-related deaths
Switzerland, May to September 2025
04
External blinds
particularly effective
stop solar energy before it reaches the glass
Climate and housing
Hotter.
Longer.
More tropical nights.
Summer heat protection is becoming an increasingly important quality factor when choosing an apartment.
Climate CH2025
01
More frequent and intense heat
The Swiss Climate CH2025 scenarios project more frequent and intense heatwaves. In a world 3 °C warmer globally, Switzerland's hottest day of the year would be around 4.4 °C warmer on average than in the 1991–2020 reference period; Zurich would experience roughly five times as many tropical nights on average. [1]
02
Summer 2025 was exceptionally warm
Summer 2025 was among Switzerland's seven warmest since measurements began in 1864. In June, some places recorded 5 to 14 hot days; during prolonged periods in August, daily highs in the Swiss Plateau and south of the Alps repeatedly reached at least 30 °C. [2]
03
Heat is more than a comfort issue
Between May and September 2025, 410 deaths in Switzerland were attributed to heat. Older people, those with chronic illnesses, pregnant women, babies and young children are particularly vulnerable. [3]
Summer heat protection is part of housing quality
When choosing an apartment for several years, summer heat protection deserves as much attention as rent, location, noise and layout.
Overheating risks
The main overheating risks at a glance
No single feature usually determines the outcome. What matters is how the floor level, glazing, shading, ventilation, construction, surroundings and building technology work together.
01
Roof and floor level
Avoid direct heat from the roof
Favourable: Middle floor, well-insulated roof or another apartment above.
Warning sign: Top floor directly beneath an uninsulated roof or many roof windows.
02
Windows
Assess glazing and window area
Favourable: Moderate glazing areas, low total solar energy transmittance and shaded façades.
Warning sign: Floor-to-ceiling west-facing windows or large roof glazing without external blinds.
03
Sun protection
Stop sunlight before the glass
Favourable: External venetian blinds, roller shutters or window shutters.
Warning sign: Only indoor curtains or internal blinds.
04
Ventilation
Allow the apartment to cool at night
Favourable: Windows on opposite sides and safe night ventilation.
Warning sign: Only one exposed façade, or windows that can hardly be left open due to noise or burglary risk.
05
Construction
Use thermal mass and insulation
Favourable: Solid, well-insulated building envelope and accessible thermal mass.
Warning sign: Lightweight construction, poorly insulated roof or substantial internal heat gains.
06
Surroundings
Assess the building's microclimate
Favourable: Trees, greenery, shade and a well-ventilated courtyard.
Warning sign: Asphalt, dark façades, large car parks and densely built streets.
07
Technology
Check passive and active cooling
Favourable: Summer bypass, free cooling, GeoCooling or quiet fans.
Warning sign: No cooling option and windows that cannot be opened.
08
Bedrooms
Pay particular attention to evening heat
Favourable: North or east exposure with quiet night-time ventilation.
Warning sign: West exposure, attic rooms or direct evening sun.
Assess the apartment
How to assess the floor, windows, shading and ventilation
Simple rules such as “attics are hot” or “north-facing rooms are cool” are not enough for a reliable assessment.
01
Floor level
Attic, top floor or ground floor?
An attic apartment is not automatically too hot. Roof construction, insulation, windows, shading and ventilation are decisive.
Without effective heat protection, however, a top-floor apartment can become very hot during the day and release stored heat well into the night.
Roof windows are especially critical because they can admit more heat than vertical windows. Check whether they have external roller shutters or heat-protection awnings and whether these work properly. [4]
Middle floors often benefit from apartments above and below. Ground-floor homes may be cooler, but you must also check safety, dampness, privacy and whether windows can be left open at night.
02
Orientation
East and west can be more problematic than south
The simple rule “south is hot, north is cool” is misleading. According to SwissEnergy, east- and west-facing rooms can also overheat.
Because the summer sun is low in the morning and evening, east- and west-facing windows often cause more problems than south-facing ones, which can be shaded more easily with overhangs or horizontal shading. [4]
Large windows provide plenty of daylight, but also solar heat. For new buildings, ask about the glazing's total solar energy transmittance and proof of summer heat protection.
North-facing or well-shaded east-facing rooms are often good choices for bedrooms. West-facing bedrooms receive heat late in the afternoon and evening.
03
Sun protection
External blinds matter more than attractive curtains
The most effective shading blocks sunlight before it reaches the glass. External venetian blinds, roller shutters, window shutters, awnings and architectural shading are therefore much more effective than curtains or indoor blinds.
Test every blind separately. Look for damaged slats, jammed motors, wind sensors and how much shade is actually provided.
Indoor curtains improve glare and privacy protection but are not an equivalent substitute for external shading.
04
Night cooling
Test cross-ventilation in practice
Night cooling removes heat stored in walls and ceilings during the day. Several hours of cross-ventilation through large windows on opposite sides are particularly effective; outdoor air is usually coolest before sunrise. [4]
Check whether a real draught is possible, whether windows open on two sides of the building and whether night ventilation is safe.
Noise, trains, restaurants, road traffic, mosquitoes and burglary risks can make a theoretically good ventilation option impractical.
Building and surroundings
Insulation, thermal mass, building technology and the urban climate
01
Building
Thermal mass and insulation
Solid walls, ceilings and floors can absorb heat during the day and release it during cooler nights. This thermal mass only works if it is not completely separated from the room by suspended ceilings, thick carpets or other layers.
Good insulation not only protects against winter cold; it also slows heat entering through the roof and façade. Even a well-insulated new building can overheat when large windows, insufficient shading, high internal heat loads and inadequate night cooling come together.
If the apartment has mechanical ventilation, ask about the summer bypass, airflow rate, controls and night operation. A comfort ventilation system is not automatically air conditioning.
Systems such as GeoCooling or a reversible heat pump are particularly positive features, provided they are professionally planned and can actually be used in the apartment.
02
Surroundings
Trees, courtyards and paved surfaces
Cities heat up considerably during the day and cool more slowly at night than the surrounding countryside. Within the same city, trees, green spaces, air corridors, elevation, dense development and sealed surfaces can make a noticeable difference.
An apartment above a large asphalt surface, on a narrow urban street or opposite a dark, sun-exposed façade will often receive more radiated heat at night than a comparable apartment overlooking a green courtyard.
Trees can provide effective shade. Also consider daylight, dampness, pollen and whether the trees will remain. A young tree in a sales brochure may provide little shade for years.
Apartment viewing
In
8
steps to test for summer heat.
A second viewing on a warm late afternoon can reveal much more than an appointment on a cool morning.
Ideal time
sunny day · around 4 to 7 p.m.
01
Arrange a second viewing
If possible, on a sunny, warm day between around 4 and 7 p.m.
02
Measure the temperature yourself
After a few minutes, measure the living room and bedrooms with your own thermometer — not next to a window, exterior wall or in direct sunlight.
03
Compare indoors and outdoors
Compare indoor and outdoor temperatures and check whether the apartment continues to heat up despite closed windows.
04
Test blinds and windows
Open all blinds, windows and ventilation openings and check the controls, condition and airflow.
05
Check surfaces for heat
Carefully touch sloping roof surfaces, ceilings and sunlit interior surfaces. Strong radiant heat is a warning sign.
06
Try leaving the windows open
Assess traffic, night-time noise, smells and security.
07
Ask the current tenants
Ask about typical peak temperatures in July and August, and whether it was possible to sleep comfortably at night.
08
Document your findings
Photograph or note the orientation, shading, window positions and available cooling technology.
Cool apartment check
Assess the risk of overheating
Select all positive features that you have actually checked in the apartment.
Cooling score:
This check is intended to help you make a decision and does not replace building-physics measurements.
+20
External shading
highest single weighting
+15
Cross-ventilation
for night cooling
100
Maximum score
eight positive features
Before signing the lease
Questions you should ask
The more specific the answers, the better you can assess the actual overheating risk.
01–06
Temperature & building
Ask specific questions about the indoor climate
How hot do the living room and bedrooms get during several consecutive hot days?
What temperatures remain at around 2 a.m. or 5 a.m.?
Have there been complaints, measurement records or requests for heat-protection measures?
Are all external blinds included in the rental property, and will the property manager repair defects?
Can air flow across the apartment through windows on two sides, and is this realistic at night given noise and safety?
How is the roof insulated, and when were the roof or windows last renovated?
07–12
Technology & costs
Clarify cooling and operation
Does the ventilation system have a summer bypass or an active cooling function?
Can the heat pump cool through floor or ceiling systems?
Are portable air conditioners allowed, and where can the exhaust hose be routed?
Would a permanently installed split air-conditioning unit be eligible for approval in principle?
What were the electricity and ancillary costs of summer cooling?
Will trees, awnings or other shading features be removed or altered in the near future?
Real-life comparison
Comparing typical apartments
01
Attic apartment
South-facing windows and external roller shutters
An attic can work well if the roof is insulated, shutters are effective, glazing is moderate and night ventilation is possible.
02
New-build apartment
Floor-to-ceiling west-facing windows without external blinds
High risk: good winter insulation alone does not prevent solar heat gain. Evening sunlight and missing external shading are problematic.
03
Older building
Middle floor with window shutters
Often favourable: solid construction, external shutters and windows on opposite sides can limit heat. Still check their condition and night-time noise.
04
Ground floor
Green courtyard
Can be pleasantly cool. Check security, dampness, privacy and whether night ventilation is actually possible.
05
Minergie
Comfort ventilation does not automatically provide cooling
The certification label alone does not guarantee active cooling. Ask about shading, summer bypass, controls and previous indoor temperatures.
Swiss tenancy law
Rented apartment too hot: What does the law say?
Swiss tenancy law sets no generally applicable maximum summer temperature for residential rooms. Under Article 256 of the Swiss Code of Obligations, however, landlords must hand over and maintain the apartment in a condition suitable for its agreed use.
If a defect is not caused by the tenant, rights under Articles 259a et seq. of the Code of Obligations may apply depending on its severity. [6] [7]
An apartment is not automatically defective simply because it becomes warm during a few exceptionally hot days. However, substantial and persistent overheating that is striking in relation to outside conditions may constitute a defect in an individual case.
There are no rigid thresholds for summer heat; what matters is the extent to which use is impaired, the building's condition and the reasonable conduct expected of the tenant. [8]
Over several days, record the room, time, indoor and outdoor temperatures, and your ventilation and shading practices. Report the problem in writing and request an assessment of proportionate measures such as external blinds, roller shutters or heat-protection film.
There is no automatic right to air conditioning. A rent reduction is likewise not automatically due; it depends on the defect, the impairment, notification and circumstances of the individual case.
256
Art. 256 CO
Suitability for use
259a
Rights in case of defects
depends on the individual case
°C
No fixed upper limit
for summer heat in residential rooms
Please note
This guide provides general information and does not replace individual advice on building physics, health or the law.
Cooling technology
Fan.
Air conditioning.
Heat pump.
Not all technical solutions cool with the same efficiency or may be installed without permission.
01
Fan
Fans do not lower the room temperature, but moving air improves perceived comfort and they generally consume much less electricity than portable air conditioners.
02
Portable and fixed air conditioning
Portable monoblock units do not need permanent façade installation, but are often noisy and inefficient because warm outside air is drawn in to replace air expelled through the hose.
A permanently installed split system in a rental apartment generally requires the landlord's written consent. Façade alterations, noise, refrigerants and cantonal or municipal permits may also be relevant.
03
Heat pumps and GeoCooling
A reversible heat pump or GeoCooling may be more efficient. Ask what temperature reduction is realistically achievable, about running costs and whether you can control it individually.
After moving in
How to keep your apartment cooler after moving in
01–04
Prevent heat build-up
Reduce incoming heat
Close external blinds early, before direct sunlight reaches the windows.
Keep windows closed during the day when it is warmer outside than inside.
Cross-ventilate for as long as possible at night and in the early morning.
Reduce use of ovens, powerful computers, lighting and other heat sources.
05–07
Reduce heat stress
Cool down and keep records
Use quiet fans where people spend time or sleep.
Record temperatures during hot spells if the apartment overheats despite appropriate precautions.
Take particular care of vulnerable people and act quickly if signs of heat stress appear. [5]
Common mistakes
The
10
most common mistakes when apartment hunting.
Never judge a feature in isolation.
01
Viewing an apartment only on a cool morning
02
Rejecting all attic apartments or assuming every new build stays cool
03
Considering only the compass direction
Do not ignore window size and shading.
04
Treating indoor curtains as equivalent to external shading
05
Assuming comfort ventilation is the same as air conditioning
06
Assuming cross-ventilation is possible without testing it
Test window positions, noise and safety in practice.
07
Failing to question “It's always warm in summer”
Ask for actual temperature readings.
08
Not recording promised cooling features in writing
09
Demanding an immediate rent reduction without temperature records
10
Installing a split air conditioner without consent
Check written consent and permit requirements.
Checklist
Checklist for finding the coolest possible apartment
Check these four areas as thoroughly as possible before applying or signing a lease.
01
Location and building
Surroundings checked
Floor level and roof construction checked
Surroundings visited in the evening
Trees and shading assessed
Heat radiated by asphalt and façades considered
02
Windows and sunlight
Solar heat gain assessed
Orientation of all main rooms noted
Roof and west-facing windows checked particularly carefully
All external blinds tested
Bedrooms protected from evening sun
03
Ventilation and technology
Cooling options checked
Cross-ventilation tested in practice
Night-time noise with open windows checked
Summer bypass or cooling explained
Operating costs and controls clarified
04
Decision
Apartment tested in real conditions
Viewing on a warm afternoon
Temperature measured personally
Current tenants questioned
Important assurances obtained in writing
Sources
Sources and information date
The climate, energy, health and tenancy-law information is based on Swiss expert and official sources.
Last updated: .
- NCCS: Climate CH2025
- MeteoSwiss: Climate bulletin for 2025
- NCCS: Heat-related mortality through 2025
- SwissEnergy: Prevent summer overheating and make use of winter sun
- Federal Office of Public Health: Protection from heat
- Code of Obligations: Art. 256 and Art. 259a et seq.
- Zurich Courts: Defects in rental properties
- Swiss Tenants' Association: Is the apartment too hot?
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Topics covered
Cool apartments in hot summers
Finding a cool apartment: What to look for when searching for a home during a hot summer Climate CH2025 External blinds Cross-ventilation
Direct answers
Frequently asked questions about cool apartments during hot summers
The key answers, explained concisely.
14
Questions & answers
North-facing rooms receive little direct sunlight. However, window size, external shading, ventilation and construction are decisive. Unprotected east- and west-facing windows can heat up considerably because of the low sun.
No. South-facing windows can often be shaded effectively in summer with roof overhangs or horizontal shading. Low evening sun hits west-facing windows more directly and can heat bedrooms well into the night.
Not necessarily. A well-insulated roof, effective external shading and good night ventilation can make an attic apartment comfortable. Without these features, however, the risk increases.
No. Good insulation helps, but large areas of glazing, lack of shading and insufficient cooling at night can cause even new apartments to overheat.
No. Check the actual shading, summer bypass, cooling options and previously measured room temperatures.
Ideally, there are large openings on opposite or differently oriented façades. Test the airflow and check whether windows can genuinely be left open at night.
Ideally on a sunny, warm late afternoon to assess summer heat. An additional evening viewing shows whether the rooms cool down again.
A single reading tells you little. Compare several rooms with the outdoor temperature and ask about measurements during prolonged heat and at night.
Yes. They stop much of the sun's energy before it reaches the glass. Indoor curtains reduce glare but are much less effective at preventing heat gain.
There is no generally applicable fixed upper temperature for summer heat. Significant and persistent overheating may nevertheless constitute a defect, depending on the individual case.
Only if there is a legally relevant defect, assessed case by case. First document the overheating and report it in writing.
No general entitlement exists. However, where a relevant defect is present, the landlord must consider suitable and proportionate measures.
Only with the landlord's written consent and after checking cantonal or municipal permits and noise regulations.
Bedrooms and children's rooms should be able to cool at night and should ideally not be exposed to unshaded west-facing sun or sit directly below the roof.
UrbanHome advisor
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Key takeaways
Conclusion: A cool apartment depends on several factors working together
No single feature identifies the coolest apartment. What matters is the combination of floor level, roof, window size and orientation, effective external shading, thermal mass, insulation, cross-ventilation, surroundings and building technology.
Visit on a warm late afternoon, take your own measurements, test windows and blinds, and get important information confirmed in writing.
Checking these points before applying reduces the risk of discovering a summer heat trap only after moving in.
Find an apartment with a comfortable indoor climate
Compare rental apartments on UrbanHome
Compare current rental apartments on UrbanHome and include heat protection, orientation and ventilation in your search criteria.
Check orientation
Compare external blinds
Consider cross-ventilation