The UK is witnessing a growing interest in the Passivhaus standard as homeowners seek ways to manage rising summer temperatures. This approach to building design focuses on extreme energy efficiency, aiming to keep homes cool in the summer and warm in the winter with minimal reliance on active heating or cooling systems.
A demonstration of this approach can be seen in a 1960s ex-council house retrofitted to meet Passivhaus standards. The homeowner, who is a non-executive director for the Passivhaus Trust, highlighted the significant investment required for such upgrades. The total cost for the work on her home amounted to approximately £80,000, excluding architectural fees. The most substantial expense was the windows, which cost £30,000, while measures to make the entire house airtight were one of the less expensive components, costing £5,000.
To manage the financial outlay, the work was completed in stages over a decade, allowing the costs to be spread out. While the home is designed to prevent heat from entering, it still requires cooler outside air to maintain comfortable temperatures internally.
Strategies employed include closing windows and curtains during the day to block direct sunlight and prevent the 'glasshouse effect.' Dust sheets are used to cover windows externally, further mitigating solar gain. However, during periods of unusually high night-time temperatures, such as a 27C evening experienced during a summer heatwave, the house's internal temperature also remained at 27C. In such instances, the homeowner noted that limited use of air conditioning might be necessary to initially cool the house, after which the Passivhaus measures could maintain the lower temperature.
The Passivhaus standard involves a highly insulated and airtight building envelope, high-performance windows, and a ventilation system that recovers heat from exhaust air. This system ensures a constant supply of fresh air while minimizing heat loss. The growing adoption of these standards in the UK suggests a potential shift in how new homes are built and existing ones are retrofitted to adapt to a changing climate.