Exciting Muswell Hill retrofit project in progress

In March, Muswell Hill Sustainability Group, received an invitation from inspirational architect Natalie Black of Enbee Architecture and Design, to see a ‘deep’ energy efficient retrofit of a home on Muswell Hill Road.

We immediately sent out to our mailing list and were delighted by the interest that we received. Natalie had scheduled a few visiting slots but she generously arranged several more to accommodate local residents intrigued to find out more about the project.

I went to visit the project on March 25th with Linda Leroy and her estate manager from Southwood Hall Estate who are actively looking at retrofit possibilities. Our expert guides were Natalie herself and Emanuel Sulea who is a director of Oasis Construction London, who are based in Muswell Hill. We donned our hi-vis and hardhats, and proceeded to the top floor of the property.

The house is a large Edwardian property on the corner of Muswell Hill Road and Woodland Rise, and had been the home of the so-called ‘vampire-hunter’ David Farrant. By the time he died in 2019, the property was in a terrible state of dilapidation with serious rain damage and rot. The new owners were determined to restore the home, and to retrofit to passivhaus standards of energy use.

They engaged North London architect Johanna Ahrberg Jackson who does a lot of work in Muswell Hill and Crouch End. Johanna does amazing interior design, but she wanted to bring in an architect with great retrofit expertise. She reached out to the Women in Architecture network and connected with Natalie Black, an architect who specialised in low carbon retrofit of homes in South London.

Working mostly over Zoom, due to the pandemic, the project was hatched. Natalie and Johanna worked on the planning application together, and had useful and productive conversations with the Haringey Planning team. The property is on the edge of the Muswell Hill conservation area, and that influenced the design – for example internal wall insulation rather than external. But the two architects found the Haringey team to be open to new approaches and building materials.

One of the key aims of the project has been to reduce the embodied carbon of the building materials used. Many building materials such as concrete, steel and bricks take a vast amount of energy to produce, therefore as little as possible should be used. This was challenging for aspects of the project – for example it became apparent early on that the the back wall of the property would need to be replaced as it was simply too damaged – how to do this in a low carbon way? As we stood on the top-floor scaffolding trying to ignore the vertigo, we listened to Natalie explain. She has used a wood fibre construction, with a very limited amount of steel resulting in a new wall that has a U-value (a measurement of energy loss) of 0.15 – that is Passivhaus standard. Using the wood fibre material she has constructed new dormer windows, and will then apply brick to the outside. Throughout she has worked with a surveyor to ensure that the walls can carry the loads required.

Natalie and her builder Emanuel described their meticulous approach to insulation. When undertaking a deep retrofit there is a risk of cold bridges – gaps in insulation where water can condense, potentially resulting in mould. Emanuel and his team are making sure that all joints are taped and that any holes (e.g when solar panels are attached to the roof) are insulated. Breathable and insulating lime/cork plaster (Diathonite) will be used as the final finish, to ensure that moisture is not trapped.

The basement of the property requires major renovation, and it was here that we saw another of Natalie’s innovations – she is using recycled glass, instead of concrete slab to build the new floors. To deal with the inevitable moisture in a basement she is using a membrane made out of recycled sea plastic.

The energy use of the resulting property will be minimal but an air source heat pump will be used, with solar panels installed to provide electricity.

The aim is to finish the project in the Summer and we can’t wait to see the finished property. But it was a privilege to see the project in progress. This is a major project, but many aspects of what we saw could be applied to smaller improvements, such as extensions or new kitchens. So it was great to see many architects visiting the project – hopefully they will be inspired to incorporate these retrofit approaches into their work.

We are hoping that the house may become one of our Green Open Homes later this year.