How to Keep Your Home Cool Without Air Conditioning

Keeping the home cool without air conditioning can be easier with a technique borrowed from hot, dry areas: hanging damp curtains at windows to cool the incoming air. This approach relies on evaporative cooling, whereby water draws heat from the air as it evaporates, producing a cooler feeling where there is airflow and low humidity.

How does the damp-curtain technique work?

A damp curtain forms a natural barrier between hot outdoor air and the interior. As the breeze passes through the wet fabric, some of the water evaporates and removes heat from the air, much like the chill felt when leaving a swimming pool wet on a hot day.

This technique is most effective in dry weather or at times when the air is less humid. If humidity is already high, evaporation is slower, the cooling effect is reduced and the room may become stuffy rather than comfortable.

Which type of curtain works best?

The most suitable curtains are lightweight, washable and able to hold moisture without dripping. Very thick fabrics take longer to dry, put extra weight on the curtain rail and may encourage mould if they remain wet for many hours.

• Choose thin cotton, lightweight linen or cotton voile.
• Avoid blackout curtains, velvet and tightly woven synthetic fabrics.
• Opt for curtains that are easy to take down, wash and dry in the sun.
• Select light colours to limit heat absorption at the window.
• Use clean water only, with no fragrance, fabric conditioner or cleaning product.

How should you use damp curtains at windows?

To apply the method, wet the curtain and wring it out thoroughly before hanging it. It should feel damp rather than saturated, preventing drips onto the floor, sockets, walls, furniture or window tracks.

Ideally, air should flow through the curtain continuously. Open another window, door or fanlight on the opposite side to create cross-ventilation, as air needs an entry point and an exit point to carry heat away.

How can you make the cooling effect last longer?

The effect continues while the curtain stays damp and air is circulating. On very hot days, the water evaporates quickly, so the method can be repeated at useful times, such as late morning, the afternoon and early evening.

• Dampen the fabric again when it starts to dry out.
• Close blinds or dry curtains on the side receiving direct sunlight.
• Position a fan towards the window, without allowing the appliance to get wet.
• Place a dry towel on the floor where there is a risk of dripping.
• Take the curtain down to dry fully at the end of the day.

Why can it work better than a fan alone?

A fan merely moves the air already in the room; when the space is very hot, it circulates that heat. A damp curtain adds evaporation to the process, so air moving through the material may feel cooler, provided the room’s humidity allows the water to evaporate.

For safe use, keep this method away from sockets, extension leads, electronic devices and walls that already show mould. In modern houses and flats, it works best as a temporary measure: a lightweight curtain, clean water, a ventilated window and complete drying after use can cool the space without creating built-up damp.