How to cool your house without air conditioning
Close by day, ventilate by night, and cool people before rooms. What actually works and why a fan can make things worse.
Without air conditioning you cannot cool a whole house during a heat wave. What you can do is slow the heat coming in, push it out when the outside air drops, and cool people directly.
The daily cycle
By day: windows closed, blinds down, curtains drawn. Every ray of sun coming through glass is heat that stays inside.
By night: once the outside air is cooler than the inside, open on opposite sides of the house to create a cross-draft. A fan in a window exhausting outward speeds up the exchange.
Reduce the heat you generate indoors
| Source | Alternative |
|---|---|
| Oven and stovetop | Cold meals or cooking at night |
| Clothes dryer | Line drying |
| Incandescent bulbs | LED lighting |
| Electronics | Switch off what is not in use |
Cool people, not rooms
- A lukewarm shower. Not ice cold: very cold water causes vasoconstriction and reduces heat loss.
- Damp cloths at the nape, wrists, temples and groin, where blood runs close to the skin.
- Light, loose, pale clothing in natural fabrics.
- Drink regularly, without waiting to feel thirsty, unless medically restricted.
- Move to the lowest floor, where the air is coolest.
When the house cannot do more
Municipalities open cooling centres during heat waves precisely because some homes cannot be cooled. Spending the peak hours in a library, a mall or an air-conditioned public building is not giving up: it is the correct move.
If there is an older person living alone in your circle, that is the person least likely to go on their own. Going to get them is the part of the plan that saves the most lives.
- Heat stroke: how to recognise it and what to do Heat exhaustion is treated at home; heat stroke is a medical emergency. How to tell them apart and what to do in the first minutes.
- Who is most at risk during extreme heat Heat does not affect everyone equally. Which ages, conditions and medications raise the risk, and how to organise check-ins.
Gear that covers this
Products that match what the guide above recommends.
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Blackout or reflective window coverings
Blocking solar radiation before it comes through the glass lowers indoor temperature far more than any fan.
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Box fan for windows
For cross-ventilation at night: it exhausts the hot air built up during the day and pulls in cooler outside air.
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Cooling towels
They cool by evaporation at the neck, forehead and wrists. They act on the person, which is where it matters.
Frequently asked questions
Does a fan help when it is very hot?
It helps while sweat can evaporate, but above roughly 95 degrees Fahrenheit it stops cooling and simply moves hot air over the skin. The CDC advises against relying on a fan alone during extreme heat.
When should windows be opened during a heat wave?
Only when the outside air is cooler than the inside, usually in the early morning hours. During the day, closed with the blinds down.
What is more effective: cooling the house or cooling your body?
Your body. A lukewarm shower, damp cloths at the neck and wrists and light clothing lower body temperature in minutes, while cooling a whole house without air conditioning is close to impossible.
Where can I go if my home does not cool down?
Many municipalities open cooling centres during heat waves. Libraries, malls and air-conditioned public buildings serve the same purpose.