Key facts
- A 1960s ex-council house in south London has been retrofitted to Passivhaus standards, allowing it to stay cool without air conditioning.
- The retrofit involved extensive insulation, triple-glazed windows, and an air-tight ventilation system.
- Energy demand in the retrofitted home has decreased by an estimated 88%, resulting in annual savings of nearly £750.
- The total cost of the retrofit was approximately £80,000, spread over ten years.
- Building new homes to Passivhaus standards is significantly less expensive than retrofitting existing ones.
As the UK faces increasingly hot summers, with projections indicating a significant rise in homes at risk of overheating, innovative solutions are being explored. One such example is a 1960s ex-council house in south London, owned by architect Marion Baeli, which has been transformed to remain cool even on 35C days, without the need for air conditioning.
Baeli describes her retrofitted home as a well-insulated flask, effectively sealed against extreme temperatures. The transformation, carried out over a decade, involved comprehensive insulation of shared walls, flooring, and the roof, along with the replacement of cavity brick walls with super-insulated timber-framed walls and the installation of triple-glazed windows. An air-tight ventilation system ensures constant fresh air, minimizing temperature fluctuations year-round. These measures have reportedly reduced the house's energy demand by 88%, leading to annual savings of nearly £750.
The Passivhaus standard, developed in Germany, aims to maintain a constant internal temperature. While effective, retrofitting a home to this standard is expensive, with Baeli's project costing around £80,000. The Passivhaus Trust acknowledges this cost, noting that building new homes to the standard is considerably cheaper, typically adding only 2-5% to construction costs. Currently, only about 1% of new UK homes are built to this voluntary standard, though this is expected to grow.
Despite the benefits, challenges remain. Many existing homes will require retrofitting, and government support schemes have faced issues. Experts suggest that even partial implementation of such measures can yield significant energy savings. For those unable to undertake major retrofits, Baeli recommends a simple yet effective strategy: shading windows to prevent heat gain.