How to Cool Down a Room

When a room is too hot to sleep or work in, a few simple changes can make a real difference. These tips start with the free ones, several of them based on NHS heatwave advice, and finish with the longer-term options.

Keep the Heat Out During the Day

• Close curtains and blinds on sunny windows. The NHS advises closing windows, curtains and blinds during the day and opening them at night when it is cooler outside. Take care with dark curtains and metal blinds, which can absorb heat.

• Shade windows from the outside. External shutters, awnings and roof window blinds stop the sun before it reaches the glass, which is more effective than a blind inside.

• Keep windows shut while it is hotter outside than in. Opening a window on a hot afternoon lets warm air in.

• Switch off what you are not using. Lights, televisions, computers and games consoles all give off heat.

• Avoid the oven on hot afternoons, and cook at cooler times of day.

Let the Heat Out at Night

• Open windows when it is cooler outside. Once the temperature outside has dropped, open up. Windows on opposite sides of the house let air flow through.

• Use the height of the house. A window open upstairs and another downstairs lets warm air rise out at the top and cooler air come in lower down.

• Stay safe. Only leave windows open where it is safe to do so.

Cool Yourself as Well as the Room

• Use a fan sensibly. The NHS says electric fans can help if the temperature is below 35°C. Do not aim it directly at your body.

• Have a cool shower or bath before bed, and keep a cold drink nearby.

• Choose cotton or linen bedding and lightweight nightwear.

• Keep a thermometer in the bedroom so you know when the room is too warm. The Sleep Charity suggests 16 to 18°C for sleep.

Longer-Term Fixes

• Shade from plants, such as trees, climbers or planters in front of south-facing windows.

• Reflective window film on the sunniest glass.

• Loft insulation to slow down the heat coming through the roof.

• Air conditioning for rooms that stay too hot whatever you do.

When to Consider Air Conditioning

If a room is still too warm to sleep in on summer evenings, despite closed curtains and open windows at night, these measures may never be enough. That is common in loft conversions, bedrooms above garages, south-facing extensions and garden offices.

A fixed air conditioning system cools the room quietly to the temperature you set, and heats it efficiently in winter. A portable unit is a short-term option, but it is noisy and less efficient. Our guides to bedroom air conditioning and portable air conditioners explain the differences.

As a guide, one room typically starts from around £2,500 and multi-room systems usually range from £5,000 to £10,000+. See how our home air conditioning installation works.

Frequently Asked Questions

What is the fastest way to cool down a room?

Close the curtains on sunny windows, switch off anything that gives off heat and run a fan. If the air outside is cooler than inside, open windows on opposite sides to get air moving. On a hot day, air conditioning is the only way to bring a room below the temperature outside.

Should I open the windows in a heatwave?

Not during the hottest part of the day. Keep sun-facing windows closed while it is hotter outside, and open them at night when it has cooled down, as the NHS advises.

Does a dehumidifier cool a room?

No. A dehumidifier makes the air drier, which can make a warm room feel less muggy, but it gives off heat as it works, so the room gets slightly warmer.

How do I keep a bedroom cool at night?

Keep the curtains closed during the day, open the windows once it is cooler outside, and use a fan. If the room still will not cool down, see our guide to bedroom air conditioning.

Call 01772 288651 or use the form below to book a free survey. We will measure the room, recommend the right system and give you a clear written quote.

Last updated: November 2026.