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

A 1960s-era former council house in south London is proving that it is possible to remain cool without relying on air conditioning, even amid record-breaking temperatures. On a recent day when the mercury reached 35 degrees Celsius, the home of Marion Baeli, a self-described “architect” who has spent over a decade retrofitting her property, was found to be 10 degrees cooler than the outside environment. The house, built decades ago, has undergone extensive modifications to meet the standards of the Passivhaus building philosophy, a German-developed approach aimed at creating highly energy-efficient structures. The transformation began when Baeli and her family moved into the property ten years ago. At that time, the house featured drafty PVC double-glazed windows and minimal insulation, leading to challenges in maintaining comfort both in the cold winter months and the sweltering summer days. To address these issues, Baeli initiated a multi-phase renovation project that focused on reducing thermal loss and preventing excessive heat gain. The initial stage of the retrofit involved insulating shared walls, flooring, and the roof. These steps helped reduce heat exchange with neighboring properties and improved overall thermal performance. A key aspect of the work was eliminating “thermal bridges”, areas within the structure where heat can escape or enter quickly, often due to breaks in insulation. For instance, gaps between rafters in the ceiling were addressed to prevent unwanted heat flow. Following the completion of the first phase, Baeli moved on to the second stage of the project. Some cavity brick walls were replaced with thinner, super-insulated timber-framed walls, significantly improving the home’s ability to retain internal temperatures. New triple-glazed windows were also installed, further slowing the transfer of heat from the outside into the living space. These changes contributed to making the house more airtight, which is essential for maintaining consistent indoor temperatures year-round. To manage the indoor air quality after sealing the house tightly, a dedicated ventilation system was added. This system ensures that the air inside remains fresh without compromising the insulation benefits achieved through the retrofit. As a result, the home experiences fewer fluctuations in temperature, whether it is a freezing winter day or a scorching summer afternoon. The impact of these modifications is evident in the energy consumption of the home. According to Baeli, the retrofit has reduced her household’s energy demand by approximately 88%. This reduction translates into annual savings of nearly £750 on utility bills. In the colder months, just one radiator is enough to heat the entire four-bedroom house across three floors, demonstrating the effectiveness of the insulation and thermal management strategies employed. Despite the benefits, the process of retrofitting a home to meet Passivhaus standards comes with considerable financial implications. The total cost of the work undertaken by Baeli amounted to roughly £80,000, excluding any additional architectural fees. Her most expensive investment was the installation of the triple-glazed windows, which cost £30,000. In contrast, making the house completely airtight was among the cheaper aspects of the project, costing around £5,000. Baeli acknowledges that the high cost of such renovations can be prohibitive for many homeowners. However, she managed to finance the work in stages over a period of ten years, spreading the expense and making it more manageable. She emphasizes that while the initial investment is substantial, the long-term savings and increased comfort justify the effort. The success of Baeli’s home highlights the potential of retrofitting older buildings to meet modern energy efficiency standards. As the UK faces increasingly frequent and intense heatwaves, solutions like those implemented in her home offer a viable path toward sustainable living. With careful planning and phased implementation, similar transformations could help millions of households across the country adapt to the realities of a warming climate.