Passivhaus Affiliate

Entopia EnerPHit Exemplar

The upgrade of a former 1930's telephone exchange is well underway, soon to become the new headquarters of the University of Cambridge Institute for Sustainability Leadership (CISL). With Passivhaus as the driving force for the scheme, the Entopia Building aims to become an exemplar for future retrofit schemes globally. Designed by PHT Patron Architype and PHT member BDP, the project seeks to raise the bar for deep green retrofit projects by incorporating embodied carbon and circular economy principles in conjunction with EnerPHit certification.

The Entopia Building, Image credit: Soren Kristensen

Acting as a central hub to facilitate growth in business, government, and academia, both in Cambridge and internationally, The Entopia Building will provide a thriving environment for staff and visitors and align with the deep-rooted values of sustainability and leadership within the institution.

We currently face the immense challenge of retrofitting over 28 million buildings by 2050 to meet our net-zero pledges. Despite conservation planning concerns, this had a considerable influence on the development of new headquarters in Cambridge, with EnerPHit prevailing as the robust and reliable route to achieve such ambitions.



The Entopia Building aims to show building owners what can be achieved with a clear focus on cutting operational, embodied and whole life carbon in existing buildings while creating beautiful and healthy places to work. The project balances the technical demands of meeting the EnerPHit standard with the sensitivities of dealing with a building in a conservation area.

Wendy Bishop, Associate & Passivhaus Designer at Architype


Key Stats

Build start date: March 2021

Completion: Expected early 2022

Project stage: In development

The Entopia Building, Image credit: Soren Kristensen


Implementing the Passivhaus fabric-first approach as the main driver of the scheme enables stringent climate targets to be met, without compromising the comfort of occupants. The Entopia Buildings is projected to deliver 75% lower heating demand compared to the average office building, with airtightness levels designed more than five times higher than the building regulation benchmarks.


The investment in building fabric is expected to increase the long-term value of the building, lower utility bills, and lower plant maintenance costs. Through the project we have been able to demonstrate the viability of measures such as internal wall insulation and triple glazing which have significantly reduced the size of the air source heat pump installation and avoided the need to upgrade electrical substation capacity. This means the only significant external alterations are the glazing and a solar power photovoltaic array on the roof. 

  Alexander Reeve, Sustainable Building Advisor, Estates Division, University of Cambridge


Heating and cooling will be provided by the central Air Handling Unit (AHU), with a 65kW integrated air source reverse-cycle heat pump, which adapts according to room temperature and CO2 sensors. Fresh air will be supplied to all spaces, providing excellent indoor air quality 24/7. This is particularly beneficial in office environments where activity levels fluctuate regularly, thus improving productivity and reducing absenteeism.


The Entopia Building, Image credit: Architype


The project was the vision of Dame Polly Courtice, CISL’s Emeritus Director, working with CISL’s John French to develop the brief, who previously led the design and build of the award-winning Passivhaus Enterprise Centre at the University of East Anglia. A pioneering Passivhaus project, the Enterprise centre holds five years of post-occupancy monitoring data. It met the RIBA 2030 targets before utilising on-site renewables. Following on from the success of this scheme, the same team, including PHT Patron Architype and PHT member BDP, were appointed to bring the Entopia Building to fruition.


Delivering the vision of The Entopia Building project is only possible through leadership and collaboration that puts sustainability objectives top of the list of priorities, and constantly innovates to achieve it, whilst not compromising cost, quality or timeline. We hope this building will provide an exemplar for the built environment, as the world moves to meet its Paris Agreement ambition to limit global warming to 1.5C. 

Prof. John French, Senior Advisor, CISL


The new CISL headquarters will provide:

  • New offices spaces, including hot desking.

  • Entertainment spaces to hold exhibitions, events, and a café.

  • A virtual hub for international offices and partner organisations, alumni, fellows, associates, researchers and visiting academics.

  • An Accelerator and Sustainability Hub to support small businesses and start-ups.

  • High tech video conferencing facilities

The Entopia Building, Image credit: Architype


Conservation vs Sustainability

Striking a balance between conservation and sustainability can often present challenges in historical locations like Cambridge, but with net-zero targets edging closer, the scheme was recognised for its climate-forward ambitions.


We confidently expect the new design modelling, material and methodology innovations at the new CISL headquarters to provide the springboard for greater collaboration at an industry and client level to fast-track the reduction of carbon emissions from our built assets.

 Paul Cossell, CEO, ISG

Key challenges included upgrading the building fabric only with internal insulation to avoid drastically altering the existing façade and disrupting the character of the building. This required thermal and hygroscopic modelling to ensure that interstitial condensation would not occur, thus causing potential damage to the building fabric over time. Taking these additional measures have made for a more high-quality design, increasing the longevity and durability of the building.

Another design challenge was sympathetically replacing the original sash windows. Triple glazed recessed frames are the most appropriate aesthetically and practically, enabling the internal wall insulation and windows to avoid complications in thermal detailing. These common challenges serve as prime lessons for other retrofit schemes with conservation constraints.


The Entopia Building existing & proposed windows, Image credit: Architype 

Existing vs proposed bay window design, Architype


The University of Cambridge was the first university to commit to a 1.5 degrees Science Based Target for carbon reduction by pledging to reduce its energy-related carbon emissions to net-zero by 2048. However, the institution hopes to go beyond this and aspires to achieve this target ten years earlier and will undergo post-occupancy evaluation for at least a year following practical completion. Alongside aiming for EnerPHit certification, The Entopia Building aims to:

  • Generate supplementary power through solar PVs.

  • Reuse lighting from another building refurbishment, re-testing and re-warrantying more than 350 LED lights.

  • Divert excess furniture from landfills avoiding 21,000kg of CO2, with others donated to local communities.

  • Target BREEAM Outstanding and WELL Gold Certification. 


Key team

Project Client: University Cambridge Institute for Sustainability Leadership (CISL) 

Architects:  Architype


Main Contractor: ISG

Certifier: MEAD

The Entopia Building construction, Image credit: MEAD


The Entopia Building is set to be the most significant project of its type in the country – proving that the most sustainable building is one that already exists. The measures we are incorporating go far beyond standard sustainable buildings and the integrated and collaborative approach to design, operation and management from all stakeholders will undoubtedly result in a truly efficient, world class facility.

James Hepburn, Principal at BDP


With Cranmer Road winning the People’s Choice Award at the 2021 UK Passivhaus Awards, Cambridge is set to gain yet another impressive Passivhaus project. The Entopia Building is due to open its doors in early 2022. We look forward to seeing how the project progresses and inspires other retrofit projects.

To discover more about the Entopia Building, don't miss our Passivhaus for Educational Buildings: University Procurement event on Wednesday 27th October. The case study will be showcased, along with other university schemes, in this standalone session focusing on the sizable and complex nature of delivering Passivhaus higher education buildings.

Passivhaus for Educational Buildings: University Procurement


Want to learn more and get into the detail of Passivhaus Retrofit? Join our hotly anticipated series of Passivhaus Retrofit Masterclass lecture series starting this winter.

Further information

The Entopia Building

Passivhaus Retrofit

Passivhaus Retrofit Masterclass lecture series

RIBA Journal: CISL’s sustainable retrofit reaches Stage 2 of the Plan of Work - 23 June 2021

ISG: World-first sustainable office retrofit begins at new CISL headquarters - 09 March 2021

15th September 2021

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