How do I keep a room cool in summer without air conditioning?

British houses are built to retain heat, which is exactly wrong for a hot week. Almost all of the effective response is about timing — doing the right thing several hours before it feels necessary.

Safety

Step by step

1. Shade the windows before the sun hits them.Most of the heat comes in as sunlight through glass. Close curtains or blinds on the east side first thing and the west side by early afternoon, ahead of the sun rather than in response to it.
2. Shade from the outside where you can.External shutters, awnings, or even a sheet hung outside stop the heat before it passes the glass. Internal blinds absorb it after it is already inside, which is much less effective.
3. Keep windows closed while it is hotter outside.Opening windows at two in the afternoon lets hot air in. Keep the house shut through the hottest part of the day and treat it as a cool store.
4. Open up once the outside temperature drops below inside.Usually late evening. Open windows on opposite sides of the house to create a through-draught, and leave them open overnight where it is safe to.
5. Use fans to move air through, not around.A fan in a window blowing out, with another window open elsewhere, exchanges air. A fan in the middle of a closed room only moves the same hot air about — although the breeze still helps you feel cooler.
6. Turn off what is making heat.Computers, televisions, chargers, lights and especially the oven. Cook outside or cold, and switch things off at the wall rather than to standby.
7. Close doors to unused rooms.Particularly a hot loft room or a west-facing room. Keeping the heat contained in one room stops it spreading through the house in the evening.
8. Deal with the loft.A loft can reach well over 50°C and radiates down through the ceiling all evening. Loft insulation works both ways — it keeps summer heat out as effectively as it keeps winter heat in.
9. Use damp air movement for immediate relief.A damp towel over a chair in front of a fan cools the air passing it. Effective in dry heat, less so in humid conditions, and it adds moisture to the room.
10. Plan the bedroom in advance.Shade it all day, air it in the evening, use lighter bedding and natural fibres, and put a fan on a timer rather than running all night against a closed window.

Tips

• Check the outside temperature before opening anything. People routinely open windows in the afternoon and make the house hotter.
• A cheap indoor-outdoor thermometer removes the guesswork about when to open up, and it pays for itself in one hot week.
• Reflective film on a south or west window costs little and makes a substantial difference to a room that bakes every afternoon.

Common mistakes

• Opening the windows during the hottest part of the day — It brings hot air in. The house stays cooler shut up until the outside temperature falls below the inside.
• Relying on a fan in a closed room — A fan does not cool air, it moves it. Without a path for hot air to leave, you are stirring the same heat around — and the motor adds a little more.

If it doesn't work

Questions people ask