Retrofit and Low Energy Strategy - London Townhouse

CWenergy’s expertise was integral to transforming this large Edwardian terraced house into a modern, energy-efficient home. The project’s centrepiece is a striking corten steel and glass extension, which houses a cutting-edge underfloor heating system powered by an air source heat pump. This upgrade significantly reduces energy bills while providing year-round comfort.

Whole-House Energy Transformation

Working alongside the architectural design team, Cagni Williams Energy developed and coordinated the low-energy retrofit strategy for this Edwardian townhouse, transforming an ageing gas-heated property into an efficient all-electric home. The project demonstrates how careful integration of building fabric improvements, renewable heating and ventilation can dramatically improve comfort while reducing operational energy demand.

Air Source Heat Pump Integration

A key objective was the complete removal of fossil fuel heating. The existing gas system was replaced with an air source heat pump serving underfloor heating throughout the remodelled ground floor. The system delivers consistent low-temperature heating, improving occupant comfort while significantly reducing carbon emissions and providing a future-ready heating solution aligned with the UK's net-zero objectives.

Designing Out Overheating

The extensive glazing of the new gallery extension required careful environmental modelling and technical design. Ventilation systems were integrated to manage potential overheating in summer, maintain indoor air quality and prevent condensation within the highly glazed space. By addressing thermal comfort from the earliest design stages, the project demonstrates how contemporary architecture and environmental performance can complement one another.

Building Fabric and Performance Upgrades

Alongside new heating infrastructure, the project incorporated targeted improvements to insulation and construction detailing to reduce heat loss and improve energy efficiency. The combination of fabric upgrades and low-carbon technologies has helped create a comfortable, resilient home with significantly lower running costs than the original property. 

Client feedback one year after occupation confirmed markedly reduced energy bills and improved year-round comfort.

Integrated Project Delivery

A major benefit of the Cagni Williams Energy approach is the integration of architecture, energy strategy and project delivery. By working alongside architects, engineers, contractors and specialist suppliers from the earliest design stages, the team ensured that energy systems, services routes and architectural aspirations could be coordinated efficiently and without compromise. This collaborative approach helped deliver a highly sustainable retrofit while maintaining exceptional design quality.