Heatwave plan: keep your home cool without AC

Build a heatwave plan for your home: shading, night ventilation and room swaps ranked by how much they cool, before you spend on a system.

Your home

Which floor?

Main rooms face

Built

Surroundings

At night, outside is

Outdoor air

Anything else?

High risk

Active cooling is justified for this home. The passive measures below still matter: they cut the size and running cost of the system you need.

You may be able to cool with good night ventilation - active cooling is optional.

Your measures, strongest first

Night ventilation: windows open overnight, closed by day
Big effect
Local noise and air quality make opening up at night realistic here. Flushing out the day's heat overnight, then shutting windows and curtains by mid-morning, is free and effective.
Free
External shading: awnings, external blinds or shutters
Big effect
Your main rooms face south, so most of the heat arrives as sun through the glass. Stopping it outside the window is the single most effective passive step.
In a flat, fittings on the outside of the building usually need the freeholder's consent, and in a conservation area possibly the council's.
£300 to £2,500
Cross-ventilation between opposite sides of the home
Worth doing
Opening windows on opposite sides, with internal doors open, moves far more air than a single open window.
Free
Light-coloured or thermal blinds and curtains, closed by day
Worth doing
Inside the glass they are less effective than external shading, but closing pale or reflective blinds on sunny windows during the day still cuts the heat noticeably.
£40 to £300
Solar-control window film
Worth doing
A reflective film on south-facing glass cuts solar gain without changing the view much, and needs no outside work.
£150 to £600
Cut heat made indoors: LED lighting, appliances run in the evening
Small help
Old bulbs, ovens, dryers and chargers all add heat. Shifting heavy use to cooler hours helps on the hottest days.
£0 to £100
Ceiling or pedestal fans
Small help
Fans do not lower the temperature, but moving air makes a warm room feel several degrees cooler for a few pence an hour.
£30 to £300

Your heatwave day

Before 8am
Close the windows once the air outside starts to feel warmer than inside.
Morning
Draw blinds and curtains on the south-facing side before the sun reaches the glass. Light-coloured linings reflect more heat back out.
Midday
Keep doors to the hottest rooms shut, and move cooking, laundry and other heat-making jobs to the evening.
Afternoon
Rooms under the roof peak late: spend the hottest hours downstairs or in a north-facing room.
Evening
Once it is cooler outside than in, open windows on opposite sides of the home to pull air through.
Night
A fan aimed across a bowl of cold water or a damp cloth near the bed takes the edge off a warm bedroom.

How this works

Your answers run through the same cooling engine as the Home Cooling Checker. It scores summer overheating risk from the factors that drive it (home type and floor, which way the main rooms face, age of construction, the urban heat island and whether the home can be cross-ventilated), then ranks passive measures by how much they help a home like yours.

Whether night ventilation is realistic uses the World Health Organization's 55 dB guideline for outdoor living areas by day and its 2021 fine-particle guideline (PM2.5 of 15 micrograms per cubic metre over 24 hours). A busy road or poor outdoor air rules it out. Cost bands are indicative UK ranges.

For a score from your home's real records, including its EPC, fabric and local noise and air-quality data, use the Home Cooling Checker.

Sources

Questions people ask

What is the best way to keep a house cool without air conditioning?

Stop the sun before it reaches the glass, ideally with external shading, keep windows shut by day and open at night when it is cooler outside, move air through the home, and cut the heat you make indoors.

Should I close the curtains in a heatwave?

Yes, on the sunny side, before the sun reaches the window. Pale or reflective linings work best.

When is passive cooling not enough?

In top-floor flats, loft rooms and single-aspect homes facing south or west, especially in dense cities, bedrooms can stay above 26°C at night despite shading and ventilation. That is when a system is worth considering.