Use the ‘Caveman Method’ to beat heatwaves in 2026

After unusually warm weather hit much of the UK during May, keeping cool has been on the minds of many at home or at work.

Timed to mark World Environment Day 2026 today (5 June, 2026), the experts at Green Doors, the Luton based sustainable door and window company, say many people make their homes and working spaces hotter during heatwaves by opening windows and doors at the wrong time of day.

So, as Britain braces for another summer of extreme heat, the company’s founder and CEO Joseph Holman is advising the use of a simple ‘Caveman Method’ to keep cool without turning to expensive, energy hungry air conditioning,  saying we should treat living and working spaces like caves during the hottest hours by shutting windows, doors, curtains and blinds to keep hot air and direct sunlight out.

While air conditioning is still uncommon in British homes, demand for cooling products is expected to rise as heatwaves become more frequent. Green Doors says we can all reduce costs and cut energy use by focusing on passive cooling methods first.

Joseph said, ‘The instinct when temperatures rise is often to throw open every window, but during the hottest hours that can actually make your home warmer. The Caveman Method works by preventing heat from getting inside in the first place.

‘World Environment Day is a reminder that some of the most effective environmental solutions are also the simplest. Keeping your home cool without consuming additional electricity reduces both carbon emissions and energy bills, while helping households stay comfortable during increasingly frequent heatwaves.

‘The best cooling system is often prevention. If you can stop heat entering your home, you reduce the need for fans, portable air conditioning units and other energy hungry appliances.’

Five sustainable ways to keep your spaces cooler this summer

Alongside the Caveman Method, Green Doors recommends several environmentally friendly measures that can help households stay comfortable during future heatwaves.

1. Close blinds and curtains before rooms heat up

Blocking direct sunlight can significantly reduce solar heat gain, particularly on south and west facing windows.

2. Open windows strategically

Keep windows closed during the hottest part of the day and open them during cooler early morning and evening periods to encourage natural ventilation.

(And, it is a good idea if you can, to open them on opposite sides of your room, so that you get a flowthrough of cooler air).

3. Reduce unnecessary indoor heat sources

Switch off lights and appliances where possible, as they generate additional heat inside the home.

4. Use external shading where possible

Awnings, canopies, shutters, trees and planting can all help block sunlight before it reaches windows.

5. Invest in long term, passive cooling improvements

Modern glazing, integral blinds, reflective glass and other heat management solutions can help spaces remain cooler naturally, without increasing energy consumption.

As a company dedicated to extending the life of doors and windows through reuse and upcycling, Green Doors, which last year won a King’s Award for Enterprise for Sustainable Development, advocates for sustainability being built into every aspect of home improvement.

‘At Green Doors, we are passionate about reducing waste and helping people make more sustainable choices,’ added Jospeh.

‘Whether it is giving a door a second life instead of sending it to landfill, or helping homeowners reduce their energy use during a heatwave, the principle is the same: making smarter use of the resources we already have.’

Green Doors has saved thousands of doors and windows from landfill and continues its mission to promote practical, affordable sustainability across the home improvement sector.

Joseph Holman is the CEO and founder of upcycling company Green Doors, which started with a door he found in a skip. The business now produces revenues of close to £2 million. 

Last year, the business saved over 3000 items destined for landfill and currently has over 1600 doors for sale in its 25,000 square foot warehouse. 

Joseph is on a mission to provide every door with a second life and to stop UPVC going to landfill.