Modernist EnerPHit Plus
| Location: London | |
| Completion Status: 2022 | Occupancy: Since Oct 2021 |
| Architect: RDA Architects | Consultant: Passivhaus Consultant: Ecospheric, Structural engineer: Michael Baigent Orla Kelly Ltd |
| Contractor: PJS Building & Maintenance | Client: Private client |
| Certification: June 2022 | Certifier: MEAD Consulting |
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A 1960s modern concrete London designer pad gets a sensitive low energy makeover. Finalist in the 2023 UK Passivhaus Awards residential retrofit category.
Originally designed by architect Michael Blackstock, the 'Modernist' has undergone an EnerPHit Plus retrofit makeover. Passivhaus retrofit standards were implemented to allow the home to face the challenges of the future and future-proof the house against rising energy bills. This home now uses 88% less energy than an average UK home.
Designed by PHT member RDA Architects, the ambitious project strived to maintain the existing structure to extend the building’s life by another 100 years, while also combining the original design aesthetic with a contemporary approach.
Key stats
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The house needed extensive repair works addressing air leakages and damp, but the the client was keen to retain many of the original features of the modernist 1960s aesthetic. The building's reinforced-concrete structure presented difficulties since it was hard to know the condition of the structure, and where the pre-stressed areas would be, until the building work was underway.
.jpg "Modernist EnerPHit Plus I RDA Architects/ Tim Soar Photography. Quote:")
The three-storey property was originally designed in the ‘upside-down’ style , with an open-plan living space and terrace sitting above the first-floor bedrooms while the ground floor contained a garage and utility area. The retrofit involved a reorganisation of the layout, including replacing the groundfloor parking area with a large welcoming lobby leading to a private study and a bedroom with ensuite, alongside a utility and plant room. The Master bedroom and two further bedrooms are on the first floor, with the living space remaining on the third floor. Distributing daylight and heat from the hotter suntlit top floors through to the darker cooler bottom floors was a challenge.
To achieve EnerPHit Plus requirements involved careful consideration of how to introduce the airtightness to the existing building fabric without affecting the overall appearance of the existing house. There were also challenges about how to resolve thermal bridging between the new triple glazed windows and the existing walls.
Construction
Different wall build-ups (using internal or external wall insulation, such as EcoCork lime plaster, ThermaLine render or wood-based Steico insulation) were needed depending on the orientation of the building. The outside of the building was fully re-rendered, alongside making good windowsills with leaking flashings. The project team aimed to retain as much of the existing structure and materials as possible, including the reuse of decommissioned pre-existing underfloor heating pipes.
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Overall U-values
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Floor: 0.128 W/m2K Floor insulation board on concrete floor. |
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Wall : 0.163 W/m2K External wall insulation board finished with cork lime plaster render. |
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Roof: 0.088 W/m2K Phenolic board Insulation, insulated plasterboard, pine cladding |
Further information can be found at the International Passivhaus Database listing
Building performance
The house's renewable energy systems meant that the project attainied EnerPHit Plus certification. The house switched to all electric heating using an air source heat pump and underfloor heating. Solar PV panels, generating 7.8kW, were integrated with a high capacity battery storage system.
The project team had to pay close attention as to how to integrate the air source heat pump with the solar PV panels and hot water storage, to ensure the most efficient energy output to the heating system at minimal demand from the grid. As well as replacing the roof, a new roof was created to include solar panels to the south side, with PV and evacuated tubes.
Predicted energy performance
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Space Heating Demand (≤ 25 kWh/m².a) |
25 kWh/m2.a |
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Heating Load |
14 W/m2 |
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Primary Renewable Energy Demand (≤ 60 kWh/m².a) |
58 kWh/m2.a |
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Airtightness (≤ 1.0 ACH @ 50 Pa) |
0.82 ACH @ 50Pa |
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Lessons Learned
- Integrate solar shading in the local authority planning process at an earlier stage.
- Stricter control on Mechanical and Electrical contractors who were in-experienced with Passivhaus EnerPHit
- Ensure that the client is fully informed with Passivhaus options before planning is approved, as the Tesla Power wall was requested after planning.
Key team
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Discover more about the project below via the awards poster & presentation.
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Further information
RIBA Journal: Retrofitting a 1960s modernist house to Passivhaus standards - 31 March 2023
Previous PHT Story: Old Timberyard gets new lease of life - 14 November 2022
Previous PHT Story: Passivhaus Mews II
Previous PHT Story: Chiswick Eco Lodge
Back to 2023 UK Passivhaus Awards
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