Creating a market for net zero multi-storey buildings

The Mustbe0 project funded by Interreg North-West Europe started in 2019, bringing together market development teams from four countries to kick-start a market for net zero multi-storey buildings.

The ambitious project has been one of the largest in the Interreg NWE programme’s portfolio, with 11 demonstrator retrofit projects in the UK, Germany, France, and the Netherlands aiming to create affordable, comfortable, long-term performance guaranteed zero carbon buildings.






Roubaix, France

Apartment with 32 dwellings

Notre Logis

Halluin, France

1960s social housing apartment with 70 dwellings

Anne Godeau school

Raismes, France

1960s primary school


Bochum, Germany

3-storey building, 24 apartments


Bochum, Germany

7 multi-family-houses, 3/4 floors, 51 apartments



2 multi-family-houses, 4 floors, 16 apartments

Arsago (Hameln)


2-storey 1930s building with 12 dwellings



4 multi-family buildings built in

1957, 3 floors, 24 apartments



3-storey apartment with 30 dwellings



2-storey apartment with 36 dwellings

Treadgold House

United Kingdom

5-storey apartment block of 38 flats


As the project draws to a close, here’s a summary of all it has achieved as well as the challenges it has faced, and the valuable lessons learned along the way.


  • France, Germany, and the UK carried out design competitions at the start of the project which have supported SMEs to develop and test their solutions for deep retrofits.
  • The transnational nature of the project has created an open space to collaborate and share innovations across countries and companies. For example, Belgium-based SME Build Up won the design competition in France and their offsite manufactured panels have been installed on an apartment block owned by social housing landlord Vilogia.
  • The first school in France to undergo an Energiesprong retrofit has been part of the project. The 1960s building has had all classrooms retrofitted, an elevator installed, fully renovated sanitary facilities and a new enlarged dining room created. As well as the improved internal comfort and carbon savings, attention has been paid to the acoustic comfort of the building and children have been involved in the decision-making process, selecting classroom colours and adding more green space in the school playground.
  • In Germany, scaffold-free assembly was successfully tested on two pilot projects, saving costs and causing less disruption for residents.
  • Resident satisfaction surveys issued in the Netherlands by housing provider Woonmeij reported lower energy bills and decreased use of medication by some tenants as a result of their homes being more comfortable, with constant temperature levels and less damp and draughts.

Long-term benefits and lessons learned

  • The Vilogia project in France developed an industrially-produced technical shaft to house the heat pumps and ventilation units, creating a highly replicable solution.
  • Vilogia has also gained experience in industrialising the building envelope in terms of technology, solutions, processes, contracting, services, and relations with residents. Based on this, Vilogia is now developing an industrialised retrofit scale-up strategy, with 4,000 dwellings due to be retrofitted in the coming years.
  • The German Market Development Team introduced and tested the Construction Team Agreement as a support tool for project matchmaking between the client and construction company, saving time and money in the design and planning phase.
  • In the UK, the Treadgold House project in the Royal Borough of Kensington and Chelsea (RBKC) has used a new tender process for the procurement of contractors. The two-stage tender approach will now be used by RBKC for future projects on the estate.

Despite facing many challenges – the Covid pandemic, Brexit, and the war in Ukraine – which have had an impact on material and transportation costs and caused delays, the Mustbe0 project has created warm and desirable places to live (or go to school in!) that are future proofed and will leave a legacy for more deep retrofits in the future.

Moreover, it is estimated that the total energy savings from the project will be 1,320 tonnes of CO2 per year.

Thank you to all partners involved in the Mustbe0 project, everyone is incredibly proud of what has been achieved. And thank you to Interreg NWE for initiating and funding the project and for all your support.

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