Bowman’s Lea Retrofit




The Bowman’s Lea retrofit provides a clear demonstration of what’s possible with an existing home. The architect / homeowner has taken a step-by-step approach to his home’s retrofit, exploring the challenges and solutions at each stage of the works, with the ultimate goal of reaching the Passivhaus high-performance EnerPHit standard for retrofits.

The EnerPHit standard is the equivalent of Passivhaus for new builds, and takes into account the inherent complexities of existing buildings such as construction of foundations, or connections to neighbouring properties.

The house is a 3-storey 1978 mid-terrace which required modernisation, and just the first stage of the step-by-step approach – window upgrades, loft insulation, some internal wall insulation and air-tightness measures – resulted in reduced heating energy demand of more than 50%. Additional energy demand reductions were achieved with additional insulation and the introduction of an MVHR system.

The works were largely completed by the homeowner / architect and focused on exploring the complexity and difficulty of each step of the retrofit, with the aim of learning what works to inform future projects. Material use and resource efficiency were also crucial factors considered in design and material choice, to ensure performance whilst minimising waste and ensuring the quality of the indoor environment.

This project is important because it demonstrates what’s possible with existing buildings, utilising a phased approach which can be completed over time as budget allows. Applying the EnerPHit standard ensures retrofitting is carried out in the right order, avoiding unintended consequences, and with measurable performance gains at each stage.

Key Features

  • Carefully detailed and scheduled step-by-step retrofit, to the Passivhaus EnerPHit standard
  • Low heating energy consumption
  • Comfortable and healthy indoor environment
  • Natural, low embodied carbon materials used efficiently, to reduce carbon footprint and waste

Sustainability Indicators

Further Information