Retrofitting a 70s home to Enerphit standards

Architect Harry Paticas used a step-by-step Enerphit process to transform his home

By Arabella St John Parker | 26 December 2021

There are 27.2 million homes in the UK and these are responsible for 25% of the UK’s energy use. As more than 98% of these are energy inefficient, with Energy Performance Certificates (EPCs) of C or below, there is a significant need to carry out radical improvements.

An effective way of improving the energy efficiency of homes is by following the Passivhaus retrofit standard. Called Enerphit, it can achieve between 75-90% savings in the energy required for heating.

Architect Harry Paticas explains how he tackled the retrofit in his own home in this Enerphit case study…

Tell us about the house

It’s a late 1970s brick-built property in Honor Oak, London that was uninsulated and unaltered in any way: even the original 1978 boiler was still in situ. As a mid-terrace house, it loses less heat than a detached or semi-detached building, which made it a little easier for energy efficiency retrofitting.

I was keen to find a project where I could do all the work myself. I’m a certified European Passivhaus consultant and although I could have chosen a smaller house and done the retrofit in one go, I wanted to experiment using a step-by-step Enerphit approach, which is the Passivhaus standard for retrofitting, and has never been done in the UK.

enerphit case study in london

Harry and his son enjoy their warm, energy efficient home. Photo: Agnese Sanvito

Where did you start?

From the top down, starting with anything that involved serious dust first, such as taking down loose plaster and ceilings. All the joist ends were taped to the external walls to make them airtight. I wanted to use some of the loft space for storage so as well as making it well-insulated with Eden Renewable Innovations’ SupaSoft, I put in a triple-sealed loft hatch.

New aluminium-clad, timber frame windows went in; they can be opened by just three millimetres at the top to act like a trickle vent in a wall. This was essential to moderate the humidity before the mechanical heat recovery ventilation system went in.

an enerphit red brick house in south london

New aluminium-clad, timber-frame windows were fitted. Photo: Agnese Sanvito

The Enerphit case study continues below…

There are 27.2 million homes in the UK and these are responsible for 25% of the UK’s energy use. As more than 98% of these are energy inefficient, with Energy Performance Certificates (EPCs) of C or below, there is a significant need to carry out radical improvements.

An effective way of improving the energy efficiency of homes is by following the Passivhaus retrofit standard. Called Enerphit, it can achieve between 75-90% savings in the energy required for heating.

Architect Harry Paticas explains how he tackled the retrofit in his own home in this Enerphit case study…

Tell us about the house

It’s a late 1970s brick-built property in Honor Oak, London that was uninsulated and unaltered in any way: even the original 1978 boiler was still in situ. As a mid-terrace house, it loses less heat than a detached or semi-detached building, which made it a little easier for energy efficiency retrofitting.

I was keen to find a project where I could do all the work myself. I’m a certified European Passivhaus consultant and although I could have chosen a smaller house and done the retrofit in one go, I wanted to experiment using a step-by-step Enerphit approach, which is the Passivhaus standard for retrofitting, and has never been done in the UK.

enerphit case study in london

Harry and his son enjoy their warm, energy efficient home. Photo: Agnese Sanvito

Where did you start?

From the top down, starting with anything that involved serious dust first, such as taking down loose plaster and ceilings. All the joist ends were taped to the external walls to make them airtight. I wanted to use some of the loft space for storage so as well as making it well-insulated with Eden Renewable Innovations’ SupaSoft, I put in a triple-sealed loft hatch.

New aluminium-clad, timber frame windows went in; they can be opened by just three millimetres at the top to act like a trickle vent in a wall. This was essential to moderate the humidity before the mechanical heat recovery ventilation system went in.

an enerphit red brick house in south london

New aluminium-clad, timber-frame windows were fitted. Photo: Agnese Sanvito

The Enerphit case study continues below…

Did it run smoothly?

Yes. I did the work in stages, detailing what had to be done in drawings each Monday, and working on the house every Sunday. It was essential to adopt a whole-house approach to avoid issues such as high humidity or CO2.

Which materials were used?

The inside of the front wall is lined with cork. By being careful when cutting it to size, I was able to insulate part of the inside rear wall as well. The back elevation cavity wall is filled with EcoBead Platinum insulation and lined with 100 millimetre-deep internal wall insulation.

Feeling how the house changed was incredible. It was cold and damp at the start, but now it’s like living beneath a huge breathable duvet.

inside an enerphit house in london

Layers of insulation include cork, EcoBead Platinum insulation and 100 millimetre-deep internal wall insulation. Photo: Agnese Sanvito

Was this a family project?

Very much so. My seven-year-old son and I leafleted the area and hosted tours of the house so neighbours could learn about the process. He also gave a presentation about cork insulation at his school. We now have a household sustainability plan to reduce our single-use plastic consumption and energy use, and to continue our retrofit journey over the next few years.

I am now a RIBA Architecture Ambassador, giving workshops about thermal performance and natural insulation in schools, and showing children how they have the power to address climate change. Winning the 2019 Alliance for Sustainable Building Products’ top award, and the People’s Prize, has been the best thing about the project so far. I want to show how people can be agents for their own change, have better quality air and better homes.

Looking for another Enerphit case study? Arboreal Architecture has also retrofitted this 170-year-old Grade II listed Victorian townhouse in Clapham and this early 20th century end-of-terrace house in south London.

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