Case Study - CISL Entopia Building

Image credit: Architype

Project summary

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 will house CISL’s Cambridge-based staff, currently spread across five buildings, and provide 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.

Reuse summary

CISL develops leadership solutions for a sustainable economy, so it needed to lead by example when commissioning its new office base. The project incorporates the original structure, with a number of material reuse elements including the steel for the PV canopy,  raised access flooring, carpet tiles and the oak reception desk. LED lights were reused from another building refurbishment, going through a full testing and re-warrantying process. Excess material and furniture was diverted from landfill. 

Image credit: Architype
Image credit: Architype

Key facts/highlights

  • 21,000kg COe saved through reclaimed materials
  • Reused steel frame for the photovoltaic canopy
  • 350 LED reused light fittings with new warranties
  • Repurposed front desk from refurbished Netflix office
  • Reuse of raised floor
  • Excess furniture and materials was diverted from landfill or donated to local communities, avoiding 85,747kg of COe.
  • 48% bio-based materials incorporated by volume
  • Use of paint with 35% recycled content
  • Project has achieved EnerPHIT standard
  • Aiming for BREEAM outstanding and WELL gold
  • 409 kg COe/m²  whole life embodied carbon of refurbished building (stage 5 construction stage assessment)

Project information

Project name

Entopia Building


Cambridge, UK

Project type 

Deep retrofit


Provision of space for offices, start-up incubator and collaborative activities.

Gross internal area (post refurbishment)

2983 m²

Project stage


Cost per sqm


Total project cost

£12.69 million

ClientCISL (Cambridge Institute for Sustainability Leadership)
ArchitectsArchitype (concept architect), Feilden + Mawson (executive architect)
Engineers and consultants

Max Fordham (M&E engineering)

BDP (M&E engineer, structural engineer and BREEAM/WELL consultant)

Cambridge Architectural  Research (structural engineer)

Reuse highlights


Steel for PV canopy


Reused steel

Donor project

Pinewood Studios, was used to run cameras on a film set


Cleveland Steel and Tubes


3.79 tonnes

Carbon saving

At least 2,000 kg COe

Key considerations

Harleston Engineering were happy to use the reused steel as long as they had the correct paperwork and it had the original CE markings.

Material/productRaised floor
ReplacementUse of existing raised floor from the building.
Carbon saving32 kg COe/m² (85,0000 kgCOe total)




Refurbished LED lights

Donor project

Cat A strip out from St James Place, London


ISG, partnered with Collecteco


350 fittings

Key considerations

The warranty would no longer be valid but the manufacturer, a specialist in lighting design agreed to honour the existing warranty, after an inspection at its factory in Essex.

The lights went from sitting within a ceiling system to sitting proud under the soffit. This also gave the chance to add uplighters, take off the end brackets and add wires to hang the luminaires.

Image credit: Architype
Image credit: Architype

Webinar recording: CISL Entopia Building - Material Learnings and Reuse

  • Discover material reuse stories from the landmark Entopia Building.
  • Hear about the successes and lessons learned from the project team.
  • Find out more about the use of bio-based and low carbon building materials, how conservation area constraints were overcome to achieve the required sustainability standards, an innovative PV array made from reused steel, plus reuse and refurbishment of LED lighting.

ASBP's Reuse Now Campaign

This case study is part of ASBP’s Reuse Now Campaign. The campaign builds upon the ASBP-led DISRUPT project, which is exploring the innovative reuse of structural steel in construction through the creation and adoption of new circular business models. Project partners and supporters include reuse stalwarts Cleveland Steel & Tubes, global construction specialist ISG, National Federation of Demolition Contractors, and Grosvenor, the world’s largest privately-owned international property business.

ASBP has been working on the topic of material reuse for nearly 10 years, with past activities including the Re-Fab House feasibility study, research with University of Cambridge identifying the barriers to structural steel reuse, and more recently, a sold-out Reuse Summit.

This previous experience is further enhanced with in-house expertise from Technical Director Dr. Katherine Adams and Research Associate Dr. Asselya Katenbayeva, who bring 25+ years of academic and industry-focussed research and development on the topics of waste, reuse and circular economy.

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