Windows closed? Windows open? What’s the best way to keep your home cool in the heatwave?

‘Generally, you don’t want to open the windows. Grab on to that last bit of cool air inside.’ Photograph: DC Images/Alamy

It’s the UK’s hottest day on record, with temperatures that reached above 40C before 1pm. As a number of schools close early and rail passengers are advised to avoid all but essential travel, those of us who can are staying home to keep out of the heat. But, with everyone desperate to keep their homes cool, a heated debate is raging: should windows be open, or closed – and what about the curtains?

As our homes become increasingly hot and stuffy, the temptation is to open a window – but, counterintuitively, Dr Andrew Shea, a senior lecturer in building physics in the University of Bath’s department of architecture and civil engineering, argues this is all wrong.