PASSIVHAUS | ENTOPIA BUILDING CIRCULAR CONSIDERATIONS The project is projected to deliver 75% lower heating demand compared with an average office a boost when needed, but its a more of a backup. During the initial feasibility process, a more traditional approach using a gas-fired boiler system with four-pipe fan coil units, and chillers, was ruled out due to the sustainability ambitions of the project. We did away with gas mains; we stripped that back and were going to an allelectric building, says Williams. In a way, were future-proofing it to get onto the Grid, because, undoubtedly, well move to all-electric buildings. If not all-air systems, the future will be a mix, with central all-air systems and heat pumps, or other electric technology, driving the main systems. As a result of the relatively small domestic hot-water (DHW) demand, the client opted to use electric showers and a mix of instantaneous and point-of-use water heaters for basins and sinks. To minimise distribution pipework losses and mitigate overheating in corridors, direct electric heating was chosen because the DHW loads in the building are relatively low. We felt that a more economical and effective solution was to use point-of-use. It also factored into maintenance and legionella risk, so we can maintain local systems a lot better, says Williams. The rooftop PV canopy, which will provide supplementary power on site, will offset some of those demands for the building, he adds. Its more a considered application, rather than a bolt-on. Challenges The biggest challenges with existing sites are constraints such as the geometry, orientation and form factor fixed variables that cannot be changed. Its a big challenge on the Entopia building because of the abnormals you find on site during construction, says Williams. He describes the property as a patchwork of previous retrofit and fit-out projects that have been added to over time, so things such as perimeter trenches get uncovered as work progresses. But he says the biggest challenge 44 April 2021 www.cibsejournal.com The spirit of the project was collaboration and integrated design, says BDPs Michael Williams, who adds that all the stakeholders and invested parties, on the client and design side, signed up to a charter to ensure everyone stuck to the brief from the outset. One such KPI was the application of circular economy principles during the retrofit. The project is one of the first to reuse more than 350 LED light fittings from another building refurbishment for the occupancy-driven, task-based lighting solution. Williams explains: The contractor had a range of existing light fittings from another project that were destined for landfill, a lot of which we were able to use on this project and theyve honoured the warranties from the point of installation. The contractor has also reclaimed the steel used for the PV canopy frame, which is a huge win in terms of reclaimed materials, says Williams. Leftover furniture has been diverted from landfill, avoiding 21,000kg of CO2, with 21,600kg of furniture donated to local communities. A third of the paint needs have been covered by a donation from Dulux of paint with 35% recycled content. of a deep energy retrofit is the risk of adding measures that might have unintended consequences for other parts of the building. For example, the Entopia Building, which is situated in a conversation area, could not be insulated externally because of planning restrictions. We have had to internally insulate, which creates the risk of interstitial condensation, compromising the building fabric and the building structure elsewhere, says Williams. To ensure the internal insulation didnt introduce a condensation risk, the team did thermal and hygroscopic (moisture) modelling of the wall build-up. We took the wall build-ups and ran them through a computer programme to simulate the moisture transfer through them. This gave us confidence that the architectural and engineering specifications would stack up, so were not introducing any risk to the existing building, Williams says. Youve got to be really careful how you address each challenge, especially with a fabric-first approach. Its about understanding the measure, the driving force behind it, and what implications it might have for other aspects of the existing design and whether we can design to accommodate it, or empathise with the existing context, while trying to achieve the difficult standards of Passivhaus. The project balances the technical demands of meeting the EnerPHit standard with the sensitivities of dealing with a building in a conservation area. When it formally opens in early 2022, CISL and the team hope the building will become an exemplar for the evolution of sustainable building refurbishment approaches in the UK. Dame Polly Courtice, founder director at CISL, said: We wanted the retrofit of our new HQ, The Entopia Building, to reflect the leadership and collaboration we engender through our projects, and to deliver the integrated social and environmental performance we advocate for as an Institute. It was therefore important for us to work with partners who would be energised by the sustainability mission and collaborate to bring their own ideas and solutions to help us achieve multiple social and environmental standards. CJ