An architect in south London has spent over a decade retrofitting her 1960s ex-council house to the Passivhaus standard, keeping it noticeably cooler in the current heatwave without any air-conditioning. On the hottest day of the summer's fourth heatwave, with outside temperatures reaching 35C, Marion Baeli's home stayed around 10C cooler inside, illustrating how such adaptations could help UK homes cope with hotter, potentially 40C, summers as more than half of British homes are already at risk of overheating.

The work, carried out in stages to spread the cost, involved insulating shared walls, flooring and the roof, eliminating "thermal bridges", replacing cavity brick walls with super-insulated timber-framed alternatives, fitting triple-glazed windows, and installing a ventilation system once the house was made airtight. Baeli estimates the retrofit has cut her energy demand by 88%, saving her nearly £750 a year, though the Passivhaus Trust acknowledges such work is costly — Baeli's total spend was around £80,000, with windows the biggest expense at £30,000 and airtighting among the cheapest at £5,000.