How this 1960s ex-council house is managing to stay cool without air con

In south London, a 1960s ex-council house managed to stay remarkably cool during a scorching 35C day, despite having no air conditioning. Marion Baeli, the homeowner and an architect, compares her house to a well-insulated flask, noting that it stays 10C cooler than the outside temperature. The house adheres to the Passivhaus standard, an international building standard developed in Germany around 35 years ago.

This standard involves sealing the home against the elements to maintain a constant temperature while consuming up to 90% less energy than typical houses. Baeli's house underwent a retrofitting process over ten years, including insulation of shared walls, flooring, and the roof, as well as installing triple-glazed windows and an air-tight ventilation system.

Although the initial cost of retrofitting was around £80,000, the Passivhaus Trust acknowledges that the expense can be challenging to manage for most homeowners. Despite this, the energy demand in Baeli's house has decreased by 88% due to these measures, saving nearly £750 on her annual bills. While more new homes are expected to be built to the Passivhaus standard in the coming years, the additional construction cost is estimated to range from 2% to 5%, depending on the type of dwelling.