How can I keep my home cool in summer?

To keep your apartment or your house cool, even during the heat of summer, two things are essential: insulating and airing.

Just like preventing the cold from getting into your home, your walls, your roof and your windows must be as airtight as possible in order to leave the heat outside. But you also have to guard against the sun’s rays. A window right in the sun, without curtains, without shutters, without blinds or without a protective film quickly becomes a real heating system.

Good air circulation is also vital. The residents of southern European towns and cities show us how. They keep all their windows firmly shut as long as the sun is out to prevent the hot air from coming in, only opening the windows at night to let the gentle night-time breeze cool the overheated stone walls. This is the same night cooling or free cooling principle which is used nowadays in the ventilation systems of large office buildings.

The exact same principle can be used at home: opening a basement window, the entrance doors and a roof window will allow a draught of cool air to come flooding in that will cool the house from top to bottom.

Protecting against the sun

• Limit the “greenhouse” effect. Draw curtains, lower blinds and close shutters, especially in rooms that are exposed to the sun. Choose pale colours. They will reflect both the light and the heat, rather than absorbing them.
• Keep bedrooms in the dark during the day.
• Fit protective films to your windows. They will filter the UV rays and reduce the effect of the sun in living rooms but still let the light in.

Keeping the heat outside

• Have your roof insulated, especially if you have bedrooms under the eaves.
• Properly insulated walls will protect you against the heat as well as against the cold.
• Keep your windows closed when it’s hot.
• Switch off unnecessary heat sources:
  • Chargers, even when they are not charging, devices on stand-by and computers all give off a fair amount of heat – unplug anything that could be an unwanted heat source.
  • Do not do any cooking in the oven and stick to cold dishes.
• Put electrical appliances that have to be used in the shade to prevent them overheating.
  • Your refrigerator and freezer act to heat the room where they are set up. If possible, move them into an adjacent room.
  • Halogen and incandescent light bulbs emit a lot of heat – switch off the lights you do not really need and replace them with LEDs.

Letting cool air in

• Air at night and create draughts to ensure that the cool air circulates around the house.
• Use a ceiling fan to stir up the hot air that has gathered overhead; this will eliminate some of the humidity created due to condensation and sweat.
• Use standing fans, without remaining directly in the draught, so that you don’t catch a cold!
• If you are drying washing, place a fan behind the dryer. Your clothes will be ready more quickly and you will benefit from the coolness of the humidity given off.

Solutions for next summer

Some solutions to improve the energy performance of your home cannot be improvised. So, for summer next year, remember to plan the works:

• Install rolling shutters, an awning, shade screens, mobile sun screens, etc.
• Put in a ground-coupled heat exchanger if you have the land. This is a stretch of tube of around twenty metres in length which is buried some 3 metres in the ground. The outdoor air is circulated through it before entering the home through the ventilation system. Underground, the temperature is 12°C, which cools the air.
• Convert your flat roof into a green roof.
• Grow some wisteria, ivy, a Virginia creeper or some Chinese knotweed on the walls that are exposed to the sun.
• Separate your veranda from your living rooms using an insulated dividing wall with an insulated door.
• Improve the airtightness of your home.
• Insulate your roof, your walls and your floors in that order.
• Repaint the walls that are exposed to the sun in white.