This world-first for a deep retrofitted sustainable office building sets new standards for low energy use, carbon emissions and impact on natural resources as well as user experience and wellbeing measured against multiple benchmarks.

The Entopia Building's brief included achieving multiple sustainable building certifications - BREEAM “Outstanding”, the Passivhaus ‘Enerphit’ standard, and Well “Gold” certification - alongside the application of ‘circular economy’ principles to minimise the volume and impact of natural and human-made resources used in the building.

The former 1930s Telephone Exchange at 1 Regent Street, Cambridge, has been transformed into an ultra-low carbon sustainability hub and new home for Cambridge Institute for Sustainability Leadership (CISL). The building houses CISL’s Cambridge-based staff, and provides a dynamic virtual hub for its offices in Brussels and Cape Town, partner organisations in China, Australia and the UAE, its global corporate partners, alumni, fellows, associates, researchers and visiting academics.

“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 warning to 1.5C." - Prof. John French, Senior Advisor, CISL

We provided M&E Engineering, Sustainability, Passivhaus, Wellbeing and Acoustics consultancy for the delivery of the retrofitted building. Working for ISG and alongside Feilden and Mawson, we took on Architype and BDP's concept design and developed it into a detailed design and continued throughout construction. We also developed the initial design in a number of ways, including:

• Moisture modelling and thermal bridging analysis - to help deliver a low-risk, low embodied energy, high thermal and airtightness performance envelope
• Lighting design – to develop the design to allow use of reclaimed fittings
• Refining the heating system design

The building fabric was comprehensively upgraded - including internal wall insulation - to reduce heat loss and work to achieve the EnerPHit airtightness targets. The wall build-up has been carefully designed to balance the benefits of increasing the thermal performance, the use of bio-based materials, and the moisture risks inherent in building against a solid masonry wall. Existing windows were replaced with high-performance triple-glazed units. Thermal bridging was carefully managed, particularly where the internal structure cuts through the internal insulation line. These measures will deliver 75% lower heating demand in comparison to an average office building, and airtightness at more than five times that required by building regulations.

The approach to building services is to tread lightly, minimising the amount of equipment required, and re-using existing items where possible. Whole-building mechanical ventilation with heat recovery is provided from a single central unit. The ventilation unit has an integral heat pump, which is used to provide efficient background heating. 

The summer comfort strategy is to combine natural ventilation with tempering of the ventilation air, using the ventilation unit. Secure night purge ventilation is also provided by the mechanical ventilation system, which, coupled with the exposed thermal mass, should limit the active cooling requirements, and help control temperatures.

Acoustic absorption is provided via class A cellulose spray ceilings and extensive acoustic panelling in meeting rooms, to provide conditions suitable for collaboration, communication and hybrid working. Noise from Cambridge city centre's Regent Street is mitigated with robust acoustic glazing and noise control is provided to ventilation systems to meet Passivhaus's stringent standards for plant noise. Our scope included the provision of pre-completion acoustic testing following the refurbishment.

The deep green retrofit is projected to result in an 80% saving in whole-life carbon emissions (over 10,000 kg CO₂e/m²), compared to a standard office refurbishment.

"The Entopia project is an exciting example of what can be achieved with a combination of an engaged client, a forward-looking brief, and a design and delivery team who commit to building for the climate emergency.

The project addresses operational carbon with EnerPHit (the Passivhaus retrofit standard), an all-electric scheme, and on-site electricity generation from PV panels. It addresses embodied carbon by using retrofit rather than new build, low embodied carbon bio-based materials rather than petrochemical-intensive products, and re-use and a circular economy approach rather than scrapping without consideration. It also addresses wider sustainability issues, including working towards both BREEAM outstanding and WELL Gold certification.

Although it’s an exceptional project at the moment, the approaches, technologies and materials being used are scalable, so we hope it becomes the norm.” - Gwilym Still, Passivhaus Leader