10 Tips For Keeping Your House Cool in a Heatwave (2026)
With UK heatwaves becoming an annual reality rather than a rare event, knowing how to keep your home cool is no longer a luxury — it's a practical necessity. The trouble is that UK buildings aren't designed for 40C temperatures, and it's not always easy to find a cool space to work, relax, or sleep in.
The good news is that you don't need an expensive air conditioning system to stay comfortable.
Here are 10 evidence-backed tips for keeping your house cool when temperatures climb.
1. Live in an old house
Modern lightweight construction with high levels of insulation works well in winter, but these buildings have little thermal mass (storage of cold-ness). Dense materials like brick and stone absorb heat slowly throughout the day and release it at night, acting as a natural buffer against rising outdoor temperatures.
2. Block out all the sun
It sounds counterintuitive, but during a heatwave it's more energy-efficient to use LED lighting indoors than to let direct sunlight stream through the glass. Solar gain through unshaded windows is one of the fastest ways to heat a room. Once the sun moves off that elevation, switch the lights off and allow indirect daylight back in.
3. Use blinds with a reflective white surface
A white or silver reflective blind, fitted snugly within the window reveal, is far more effective than dark curtains loosely hung across the opening. Dark fabric absorbs radiant heat and re-radiates it into the room. A well-fitted reflective blind bounces solar energy back out before it has a chance to warm your interior.
4. Open windows at night
Night-time is your opportunity to flush stored heat out of the building fabric and bring cooler air in. To do this safely, consider fitting window restrictors or security stays, which allow ventilation while limiting the opening to a few inches.
5. Open loft hatches after dark
Hot air rises, and your loft is often the hottest space in the house. Opening the loft hatch at night creates a natural stack effect, drawing warm air upward and out. Important caveat: only do this once the sun is off the roof. Opening the hatch while the roof is baking hot will push that heat downward into your living spaces.
6. During the day, only leave windows open if it’s cooler outside than inside
This is the most overlooked rule of passive cooling. Heat generated inside your home — from appliances, cooking, and occupants — is minimal compared to the heat load carried by hot outdoor air. Use a simple indoor thermometer alongside a weather app to track external temperatures, and only open windows when the air outside is genuinely cooler than the air inside. In practice, this often means closing windows before you leave for work and waiting until the evening to ventilate.
7. Crack windows open slightly when using internal blinds
When a blind is closed, a pocket of superheated air builds up in the gap between the glass and the fabric. Left sealed, this heat conducts through the blind and into the room. Opening the window by just a centimetre or two allows that trapped hot air to escape through natural buoyancy — a simple but effective improvement.
8. Consider fitting external shading
Stopping sunlight before it reaches the glass is significantly more effective than trying to manage it once it's inside. An awning, canopy, or brise-soleil on south and west-facing walls can dramatically reduce solar gain through those elevations during the hottest parts of the day.
9. Grow climbing plants on sunny walls
A well-established climber — ivy, Virginia creeper, wisteria — creates a living insulating layer between direct sunlight and your brickwork. This shades the thermal mass of the wall, slowing its rate of heat absorption during the day. As a bonus, deciduous climbers drop their leaves in winter, allowing the sun to warm the wall when you want it to.
10. Go French! External shutters look great
External shutters are the most effective passive shading solution available, and they're commonplace across southern Europe for good reason. By intercepting sunlight before it reaches the glass, they prevent heat gain at source rather than trying to manage it inside the room. They also add security, weather protection, and a great deal of character to a building's facade.
Talk to us about HVAC and Air Conditioning
If your existing ventilation system needs some TLC or you're looking to install a new unit altogether in a non-residential building, get in contact with us today. We'll discuss the best-suited solutions to keep your space cool in these warmer months.
See more: AHU Servicing, New AHUs.
