3 April

Older houses often had unflued gas or coal fires, and without these vents people would potentially die from the exhaust gases. I’ve had a few air con specialists tell me to seal these up, because they ‘lose heat’. But actually I think they point to something we’ve forgotten, that’s really important. Ventilation. Fresh air. Obviously a big issue with Covid, but even without it many houses now have very little fresh air, particularly in colder months. Older homes had high ceilings and these high vents, not to control heat (a common explanation), but to create an updraught. Which can help control heat, but the focus was much more about keeping fresh air moving through the room. They’re ‘trickle vents’. They allow small amounts of air to move through them, so that even in winter you can heat and have ventilation, at the same time. Some window manufacturers now build trickle vents into window frames, for the same reason, though you don’t get the same updraught. By creating a vertical movement of air it also helps move germs and pollution upwards, away from other people. This can be more effective than cross-ventilation, which is often used but creates a horizontal flow of air, that can carry dirty air from person to person.