7/7 – Staying cool and safe when it’s hot out
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Staying cool and safe when it’s hot out
Hot days and heatwaves can make homes uncomfortable and sometimes unsafe.
When indoor temperatures stay high for many hours, especially above 27–28°C, the body struggles to cool itself. If temperatures stay above 30°C, health risks increase, especially for older adults and people with medical conditions , or those who spend most of their time indoors.
This page explains:
Actions for hot days
Small changes can reduce indoor temperature and help your body cope with heat.
Close curtains, shutters, or blinds on sunny windows during the day
Ventilate when outdoor air becomes cooler (usually evening or early morning).
Drink water regularly, even if you do not feel thirsty.
Rest in the coolest room of the home.
Use a fan or create air movement if possible.
Why heat indoors can become risky
Your body cools itself mainly by sweating.
When the air is very hot, or humid, sweat evaporates more slowly. This makes it harder for the body cannot release heat efficiently.
Long exposure to high indoor temperatures can lead to:
- dehydration,
- dizziness,
- headaches,
- fatigue and weakness,
- difficulty concentrating,
- worsening of existing medical conditions.
Some medicines can also reduce the body’s ability to regulate temperature, making it harder to cope with heat.
That is why managing indoor heat is not only about comfort- it is also about safety.
Warning signs that heat is becoming dangerous
Seek medical help or contact emergency services if someone shows:
- confusion or unusual behaviour,
- fainting,
- very hot skin,
- severe headache,
- breathing difficulties,
- chest pain.
Do not wait if symptoms are serious.
How heat builds up indoors
Heat can enter and remain inside homes in several ways.
During the day:
- Sunlight enters through windows
- Walls and floors store heat (Heavy materials like concrete, brick, or stone store more heat)
- Appliances and electronics release heat
- Windows often remain closed
Even when outdoor temperatures drop at night, the heat stored in walls and furniture may remain inside
If the home is not ventilated during cooler hours, heat can build up day after day.
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Why a room can feel hotter than the thermometer
Just like in winter, how hot a room feels does not depend only on the air temperature. Several factors work together to affect comfort:
- the air temperature,
- how hot the walls, windows, and other surfaces are,
- how much air is moving in the room,
- how humid the air is,
- what you are wearing,
- and how much heat your body is producing.
Hot surfaces and sunlight
Sunlight is one of the main reasons homes become hot. When sunlight enters through a window:
- it passes through glass
- it hits floors and walls
- these surfaces absorb the heat
- the heat is slowly released into the room
This means that even if the air temperature is the same, surfaces near a sunny window can become much hotter.
Your body absorbs heat from these hot surfaces. That is why sitting near a sunny window often feels much hotter than sitting in the shade.
What can you do?
Blocking the sun before it enters the room is very effective. For example, external shading (shutters, awnings) can block 60–90% of this solar heat before it enters the room. Internal curtains help, but are less effective because sunlight has already passed through the glass.
Natural ventilation and air movement
Natural ventilation means cooling your home by opening windows or doors to let fresh air move through it. Opening windows and doors helps in two ways:
- it removes warm indoor air
- it increases air movement around your body
There are two main types:
- Single-sided ventilation: One window is open. Air moves slowly in and out.
- Cross ventilation: Two openings on opposite sides of the home are open. Air flows across the room.
Cross ventilation usually cools a home more quickly, especially during the evening or night when outdoor air is cooler.
Air movement (fans)
Fans do not reduce the air temperature, but they move air across your skin.This helps sweat evaporate and allows your body to release heat more easily.A fan can make a room feel noticeably cooler even if the thermometer does not change.
Humidity
When humidity is high, sweat evaporates more slowly. This makes it harder for the body to cool down.
For example, a day with 28°C and high humidity can feel hotter than a day with 30°C and moderate humidity. Night ventilation can help reduce both temperature and humidity.
Hot surfaces and sunlight
Sunlight is one of the main reasons homes become hot.
When sunlight enters through a window:
- it passes through glass
- it hits floors and walls
- these surfaces absorb the heat
- the heat is slowly released into the room
If indoor temperature remains above 30°C for many hours and symptoms appear, seek medical help.
This means that even if the air temperature is the same, surfaces near a sunny window can become much hotter.
Your body absorbs heat from these hot surfaces. That is why sitting near a sunny window often feels much hotter than sitting in the shade.
What can you do?
Blocking the sun before it enters the room is very effective.
For example, external shading (shutters, awnings) can block 60–90% of this solar heat before it enters the room. Internal curtains help but are less effective because sunlight has already passed through the glass.
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Natural ventilation and air movement
Natural ventilation means cooling your home by opening windows or doors to let fresh air move through it.
Opening windows and doors helps in two ways:
- it removes warm indoor air
- it increases air movement around your body
There are two main types:
- Single-sided ventilationOne window is open. Air moves slowly in and out.
- Cross ventilationTwo openings on opposite sides of the home are open. Air flows across the room. Cross ventilation usually cools a home more quickly, especially during the evening or night when outdoor air is cooler.
Air movement (fans)
Fans do not reduce the air temperature, but they move air across your skin.This helps sweat evaporate and allows your body to release heat more easily.A fan can make a room feel noticeably cooler even if the thermometer does not change.
Humidity
When humidity is high, sweat evaporates more slowly. This makes it harder for the body to cool down.
For example, a day with 28°C and high humidity can feel hotter than a day with 30°C and moderate humidity.
Night ventilation can help reduce both temperature and humidity.
Keep heat out during the day
Blocking heat before it enters the home is one of the most effective cooling actions. During the hottest hours (usually 12:00–18:00):
- close shutters, blinds or curtains on sunny windows
- keep windows closed if it is outdoor air is hotter than indoors
- stay in the shadiest room of the home if possible.
- reduce appliance use during peak hours
Even common appliances release heat:
- TV: 100–200 W
- Refrigerator: 100–300 W
- Cooking: 1000 W or more temporarily
Reducing internal heat gains helps limit overheating. Blocking heat is easier than removing it later.
Bring cooler air in at the right time
When outdoor air becomes cooler than indoor air (usually in the evening or at night):
- open windows for 10–20 minutes, if safe
- if possible, open two windows on opposite sides to create airflow (cross ventilation)
This is called cross ventilation and helps to remove warm indoor air faster.
Short, strong ventilation is more effective than leaving one window slightly open all day. If opening windows is difficult and you live alone:
- use the window that is easiest and safest for you to reach
- even one short opening in one room is better than none
If your home has a mechanical ventilation or exhaust system, use it to help move warm air out.
Keep your body cooler and reduce heat stress
Cooling the body directly is often easier than cooling the entire room.
You can try to:
- drink water regularly (small sips during the day)
- use a cool or damp cloth on your neck, wrists or forehead
- take a lukewarm shower, if possible
- wear light and loose clothing
- avoid heavy physical effort during the hottest hours (usually 12:00–18:00)
If you forget to drink:
- keep a bottle or glass in your main living area
- use a phone reminder if helpful
Create a “cool corner” in your home
If your home becomes very warm, prepare a small area where you can rest during the hottest hours. A cool corner can be:
- the room with the least sun
- a space with curtains closed
- an area with some air movement
- an area with easy access to water and seating
This can help reduce fatigue if you have limited energy or mobility.
Sleep better during hot nights
Hot nights can reduce sleep quality and increase health stress.
You can try to:
- ventilate the bedroom in the evening or early morning
- keep curtains closed during the day
- use light sheets instead of heavy blankets
- cool your body before bed with a shower or a damp cloth
Even small temperature reductions at night improve sleep quality.
If you use medical or assistive equipment
Heat can also affect equipment such as:
- medical devices
- chargers
- mobility equipment
To reduce risks
- keep equipment away from direct sunlight,
- ensure air can circulate around devices that become warm,
- avoid placing equipment near windows that receive strong sun.
If you notice that heat affects how your equipment works, contact your service provider.
Why indoor heat matters for long-term health
Spending many hours in very warm indoor spaces can affect health over time.
Researchers study these impacts using population health measures such as DALYs.
This method was explained in the winter module (link), where it is used to estimate the health impact of cold homes. The same approach is also used to study indoor overheating in summer.
Even small improvements matter!
Heatwave emergency plan
During extreme heat:
- Close curtains or shutters during the day
- Ventilate after sunset and early morning
- Use a fan if available
- Drink water regularly
- Reduce activity during 12:00–18:00
- Ask someone to check on you, or check on others
If indoor temperature remains above 30°C for many hours and symptoms appear, seek medical help.
A checklist for hot days
- Close curtains or shutters on sunny windows
- Ventilate when outdoor air is cooler
- Drink water regularly
- Use cool cloths or showers
- Rest in the coolest room of the home
- Keep medical equipment away from direct sun
Optional technical solutions (if changes to the home are possible)
In some homes daily habits may not be enough to keep indoor temperatures safe during heatwaves.
If you own your home or your landlord agrees to improvements, some technical solutions may help.
You do not need to organise these changes alone. A technician, installer or housing service can support you.
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External shading systems
External blinds, shutters or awnings are very effective at stopping heat before it enters the home. This is one of the most effective ways to reduce overheating. Accessibility tips:
- choose systems that can be operated easily (motorised or low-force controls)
- make sure switches or remote controls are easy to reach
Mechanical ventilation or night ventilation systems
Some ventilation systems remove warm air automatically during cooler hours, such as at night. These systems can:
- reduce heat build-up indoors
- improve air circulation
- reduce the need to open windows manually
Accessibility tips:
- useful if opening windows is physically difficult
- choose system with simple controls and clearly labelled
- check who will be responsible for maintenance
Portable cooling devices (with caution)
Portable air-conditioning units or cooling devices can help in one room. Important accessibility and health notes:
- avoid heavy units that need to be moved often
- choose devices with simple controls
- make sure filters and water containers are easy to clean
- avoid cold air blowing directly on your body for long periods.
Window improvement and solar protection films
Improving window performance or adding solar control films can:
- reduce heat entering through glass
- improve comfort in rooms exposed to strong sun
Accessibility tips:
- installation should be done by professionals
- avoid solutions that require frequent manual adjustments
Ask for a heat and comfort assessment
Local energy or housing services may offer assessments to:
- identify rooms at high overheating risk,
- recommend suitable shading or ventilation improvements,
- support requests for building improvements.
This is especially useful if you live in rented or social housing