CISL Entopia Building – Material Learnings and Reuse

Date: Thursday 29th September   Time: 12:00-13:45   Location: Online (Zoom)

About this event

The Cambridge Institute for Sustainability Leadership (CISL) needed a headquarters that reflected its own values, so it set about a deep green retrofit of the Entopia Building, proving along the way that the most sustainable building is probably the one that already exists. The 1930s former telephone exchange in central Cambridge, used for offices since the 1990s has been refurbished to the Passivhaus EnerPHit standard and BREEAM Outstanding, and is aiming for WELL Gold certification.

  • 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.



Wendy Bishop

Wendy Bishop

Roy Fishwick

Roy Fishwick

Cleveland Steel and Tubes
Peter Kelly

Peter Kelly

Group Director of Sustainable Operations
Anna Nitch-Smith

Anna Nitch-Smith

Chief Operating Officer
Cambridge Institute for Sustainability Leadership (CISL)
Neil Turner

Neil Turner

UK Technical Sales Manager
Ecological Building Systems


12:00 WelcomeSimon Corbey, Director, ASBP

12:05 The client perspectiveAnna Nitch-Smith, Chief Operating Officer, Cambridge Institute for Sustainability Leadership (CISL)

12:25 The architect’s perspective: Learnings from material choice, reuse, and circular economyWendy Bishop, Associate and Passivhaus Designer, Architype

12:45 Reuse success stories: Reconditioned lighting and the PV arrayPeter Kelly, Group Director of Sustainable Operations, ISG

13:00 Supplying reused steel for the PV array and an update on the ASBP project DISRUPT funded by Innovate UKRoy Fishwick, Managing Director, Cleveland Steel and Tubes

13:15 Specification & Supply of the natural insulation systems & airtightness detailing & installation and sharing learning on working towards the Well Standard Neil Turner, Technical Sales Manager, Ecological Building Systems

13:30 Q&A

13:45 Finish

Key information

Date: Thursday 29th September

Time: 12:00-13:45

Cost: ASBP members – FREE, registration essential; Member of partner organisation* – £20 + VAT; Non-member/General admittance – £30 + VAT

* ACAN, AECB, Building Performance Network, BWF, CIBSE, Fit for the Future, FIS, Good Homes Alliance, Passivhaus Trust, STBA, The Green Register and Woodknowledge Wales.

Location: Online (Zoom)

About the Entopia Building deep green retrofit

Aspirational targets and standards:
  • An ambitious embodied carbon target of 300kg/CO2/m² was set over the building’s assumed 100-year life
  • Refurbished to the Passivhaus EnerPhit standard
  • Refurbished to BREEAM Outstanding
  • Aiming for WELL Gold certification
A new precedent in window design

Modelling revealed that the glazing bars and frame of the Georgian-style windows hogged more than 40% of the window area. Architype proposed replacing the windows with large, tilt-turn ones without any mullions or transoms and recessed behind the window opening so barely any of this was occupied by the frame. This would improve daylighting factors inside the building by between 70% and 80% and offer better thermal performance than windows divided up into smaller panes or fitted within the window opening.

The Cambridge planners took exception to the loss of the Georgian-style windows, so they recommended refusal. Fortunately, the planning committee disagreed with the planning officers and approved the proposal, setting a new precedent for a conservationa rea.

“One of the reasons for approval was this was an exemplary project that was addressing the climate emergency,” says Alex Reeve, the sustainable buildings adviser for Cambridge university estate management.

Reuse stories
  • Reused steel in the new PV array.
  • 350 recalimed LED light fittings. These were inspected by the manufacturer and given a new warranty.
  • The reception desk was reclaimed from Netflix
  • Leftover furniture in the building has been diverted from landfill avoiding 21,000kg of CO2, with 21,600kg of chairs, tables and storage cabinets donated to local communities.
  • A third of the building’s paint needs have been covered by a donation from Dulux of paint made from 35 per cent recycled paint content.
Bio-based materials

Two 20mm-thick layers of Diathonite sprayed to the inside of the brick wall. Made from natural hydraulic lime, diatomaceous earth and cork and supplied by Ecological Building Systems, this primarily acts as the airtightness layer but also has insulating properties. A 40mm layer of Gutex woodfibre insulation board was fixed over the Diathonite. This realtively thin layer allowed the building to meet the EnerPhit standard as the building has a large floor area relative to the wall area, which means smaller heat losses.


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