Key impact - Overheating

We're always being told that global warming is a problem, but in the middle of a classic miserable British summer, it's hard not to wish for a little bit more warmth.

This makes it difficult to take overheating seriously, but if you're very old, very young, or ill, overheating can be dangerous. People suffer most when the temperature stays high (over 30°C) for a few days, without cooling down much at night. We can usually cope with higher temperatures in the day, but if it stays high overnight, our bodies don't get a chance to recover, and that's when vulnerable people suffer.

Even if you're fit and healthy, if your home is too hot it will stop you sleeping properly and make relaxation difficult. Traditionally, we've coped with stifling temperatures by opening windows. This is fine if it's cooler outside, but once the temperature outside rises above 28°C, ventilation just replaces warm air with more warm air, and doesn't have much benefit.

These outdoor temperatures wouldn't be considered unusual in other countries, but houses there are designed differently. Plenty of natural ventilation, light-coloured walls, and small shuttered windows keep buildings cool in the heat of the day. In the UK, staying comfortable has usually been a problem at the other end of the year - keeping warm in wintertime. So our homes aren't well suited to the climate we're going to experience, and many will experience severe overheating.

Why not just fit an air conditioning unit?

One way to keep cool is to fit an air conditioning unit. They're becoming common in offices and cars, but there are good arguments for trying to avoid them at home. They're heavy power users, so running one means higher energy bills and more carbon being pumped into the atmosphere - contributing further to climate change. They can also be noisy, require maintenance, and pump waste heat into your surroundings. This means your neighbour will probably have to close the window to get some sleep, increasing their temperature, and as a result may well simply go out and buy their own air conditioner.