The UK’s first step-by-step EnerPHit

A step-by-step retrofit of a terraced house in Honor Oak, Lewisham, with a focus on using natural materials and inspiring retrofit works in the local neighbourhood

A man and a child sit on the floor in a bedroom, playing with a toy car and toy airplane against the wall. There is a bed to the left of the image and a bookshelf with brightly coloured books. There is a window above where the man and child are.

The project is a whole-house deep retrofit of a 1978 mid-terrace townhouse and is the first certified step-by-step Enerphit (Passivhaus standard for retrofit) in the UK. The 3 storey property was purchased in 2016 though only a very small budget was available to carry out building work. The first step in the phased renovation was completed in May 2018 with a resulting reduction in the space heat demand of 53%.

Image of a living room with a large sliding window in the background set inside a brown cork wall. A man sits in a chair reading a book on the left of an image, while a child plays piano on the right of the image. There is a large plant on the left.
Architectural detail of the Bowman's Lea retrofit project. The detail shows how the existing building has been retrofitted and insulated to ensure there are no thermal bridges. It is a pencil and watercolour image, with annotations in pencil.

The building work on the project has been largely carried out by the homeowner and has focussed on exploring the complexity and difficulty of step-by-step retrofit, learning by doing as a way of informing best building practice, specifying materials with low embodied carbon, reducing construction waste, and improving indoor air quality.

Bowman's Lea shown as a whole street of individual terraced houses, with the house numbers given and photos of the residents of the houses included. There are colourful shapes that make the image more fun!

Talking to neighbours throughout the process has inspired the beginnings of retrofit measures on other homes on the street, from solar panels, to triple glazing. As all the properties on the street share a very similar typology, a similar approach to retrofit can be used, helping save time in terms of retrofit assessments and identifying the best materials and products for the retrofit.

Multiple images showing neighbors, architecture professionals and school students visiting Bowman's Lea and learning about the retrofit works being carried out.

Students from local schools have been able to visit the project throughout, helping them to learn about sustainability in architecture and the importance of retrofitting homes.

Street Elevation of Bowman's Lea. The house is a 1980's terrace with yellow framed windows and and yellow door on the ground floor. The first and second floor windows are partly covered by a yellow fabric solar shading system.

As well as improving insulation, adding in Mechanical Ventilation with Heat Recovery (MVHR), an Air Source Heat Pump (ASHP) and LED Lighting, all to improve comfort and reduce energy usage, solar shading has been added to reduce summer overheating. The yellow sheets can easily be attached to the outside of the window during hot summer days, reducing the solar gain through the windows, but still allowing air flow to help ventilate the house.

A man and a child play piano in the living room of the retrofitted house at Bowman's Lea. Visible in the background is a cork wall and a triple glazed sliding door is visible on the left.
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