What are the triumphs and challenges of deep retrofit – the process of making a building sustainable in conversion and use?
RIBA charts the development of the Entopia Building for the Cambridge Institute for Sustainability Leadership
The RIBA journal has recently released a study, across the lifecycle of our Cambridge Institute for Sustainability Leadership project, to find out what are the triumphs and challenges of a deep retrofit are.
Starting in July 2021 – RIBA have tracked the process and progress of the project and considered the fundamental questions of sustainability that must be interrogated at each point, through the RIBA Plan of Work (POW), to create a powerful sustainable building exemplar. They have examined POW Stages 0 to 5 of this ambitious, £12.8 million retrofit.
We chart ISG’s involvement from stage three onwards.
Stage 3: Spatial coordination
Stage three is officially labelled spatial coordination in the RIBA Plan of Work. And certainly, there was a lot of testing of initial concepts in the design development for the deep retrofit for Cambridge Institute for Sustainability Leadership.
This stage is where the project manager, along with Architype as architect and BDP on MEP, have been preparing the project for transition to the design and build stage, for ISG and its team.
As lead contractor ISG came in at the pre-construction stage and liaised with key stakeholders of the project. With this being a refurbishment, the level of complexity is elevated.
Wendy Bishop of Architype recalls: ‘There were contractors coming to find out about the building and new approaches to the job.’
Alongside the financial process there was delivery on sustainability targets. She was interested to see how keen contractors were and whether it seemed as though they would give attention to detail. The structure of the design-and-build teams on offer varied – and unlike some of the competing contractors ISG’s, Passivhaus expertise sat not with the architect, Feilden + Mawson, but with the MEP engineer Max Fordham.
Following the end of stage 3, ISG was appointed contractor on the stage 4 design and planning was submitted in early summer 2019.
Stage 4: Technical design
It was during stage four – shortly after delayed planning approval gave the ok to proceed – that Covid hit. The progress on the project did not stop though, whilst it was slowed due to capacity allowed on site – technical works still took place. First up was the insulation of the solid masonry wall.
It was a knife-edge balancing act to meet the combined challenges of airtightness, internal insulation of solid masonry wall, thermal performance, and moisture risk. Different underlying wall types drove different approaches to build ups in this complex insulation job, whilst the biggest challenge perhaps came with the initial strip-out.
Software package Therm was used to model the thermal bridges and help work out how far it was worth extending the insulation into the building, above and below the soffit. “Each cold bridge had to be identified and a solution for insulating it developed. The detail would then be thermally modelled to understand the impact on heating demand in order to maintain a comfortable margin within Passivhaus requirements.’ Chris Read, Senior Architect, Feilden + Mawson.
Keeping the total in-use energy in line with EnerPHit’s complex total energy metric (PER) required working with the client, agreeing low flow showers, and as much detail as possible on copiers, printers and IT equipment.
There was a guessing game where the numbers were trumped by estimations of human behaviour. Would a sustainably committed workforce fill the kettle just enough and not too much?
“Each cold bridge had to be identified and a solution for insulating it developed. The detail would then be thermally modelled to understand the impact on heating demand in order to maintain a comfortable margin within Passivhaus requirements."
Chris Read, Senior Architect, Feilden + Mawson
Stage 5: Manufacturing and construction
Having now reached the construction stage, ISG take control of the site. Peter Kelly, Group Director of Sustainable Operations, took a lead role in the Entopia project, something he hadn’t done previously.
“Every decision was made with sustainability in mind. It is the first time in my working life that this has happened.”
Team collaboration was vitally important for the project lead with a vairtey of strategies in place to ensure everyone was singing from the same hymn sheet. There were training days, two, three-minute videos of wall build-ups, which ISG’s visualisation team created and mock-ups for air tightness. With not only Enerphit targets to hit but also Breeam and Well Building standards, there was endless checking that any proposed substitute products chains – were bio-based with low VOCs and low embodied carbon.
With circular economy a big part of the project, with ISG playing a big part in sourcing re-used materials and objects for the project. It wasn’t a case of grabbing something from a skip, first there was finding them and then ensuring they were checked and re-conditioned as necessary.
First was the reception desk; originally from the Copyright Building in central London, where ISG was doing a refit for Netflix. This was going to be skipped due to a layout change for the new reception area, but instead went back to its makers at Benchmark to be adapted for Entopia.
A steel structure, that was no longer in use at a London film set, was repurposed and brought to Cambridge and has since been used as PV canopy for Entopia. Whilst the LED lights came from an ISG client who was stripping out a CAT A fit out. The complication was not only that the warranty would no longer be valid but that the lights would be going from sitting within a ceiling system to sitting proud under the soffit. But the manufacturer, Specials Lighting Design agreed to honour the existing warranty, after an inspection at its factory in Essex.
These examples show the huge waste generated by discarding still-performing objects in the industry, sometimes after little or no use. ‘The circular economy has got to be how we do things in future,’ says Kelly. ‘We can’t just downcycle, there has to be a marketplace for perfectly reusable materials.’ One of ISG’s targets is an Ebay-style system for re-used materials but he admits there is a problem in scale. And there is the complexity compared to buying an off the shelf product. ‘You need a bit of luck, a bit of skill and a bit of charm,’ admits Kelly. Persuasion and making things sound possible are part of the job.
This was originally published on the RIBA Journal website - You can read the full publication here
"Every decision was made with sustainability in mind. It is the first time in my working life that this has happened.”
Peter Kelly, Group Director of Sustainable Operations
A world's first
CISL recently launched their ‘The Entopia Building, CISL's ultra-sustainable home in the heart of Cambridge’ case study, which document the innovations, best practices and new insights that emerged from the project.
‘From the outset, the Entopia Building project aspired to demonstrate and highlight how global trends and challenges can be addressed meaningfully at the scale of a single building. The building embodies our mission to develop leadership and solutions for a sustainable economy.
With a reputation as one of the most environmentally burdensome industries, the built environment sector needs to find a way to lead the transition to a sustainable economy. Through the Entopia Building, CISL are demonstrating the multitude of benefits that can be delivered by re-purposing existing building stock.
By targeting ambitious sustainable building standards including BREEAM (Outstanding), the Passivhauss 'EnerPHit' standard (awarded in July 2022), and WELL (Gold) certification, alongside the application of 'circular economy' principles, this project has achieved its goal in delivering an exceptionally efficient home for CISL and the Canopy incubator that places wellbeing at its heart.’
