Global exemplar

As the hoardings communicated during the refurbishment, the building is not an ordinary office retrofit, but urgently needs to become one if the climate emergency is to be addressed. With buildings responsible for 40% of global carbon emissions and 50,000 UK buildings demolished every year, a standard demolition and rebuild approach can no longer apply. The whole industry needs to rethink how to design and construct buildings, with carbon impact, circularity and wellbeing being the rule not the exception.

The Institute is a global leader in sustainability, and with the design team developed challenging environmental and wellbeing targets of EnerPHit (the Passivhaus standard for retrofit) WELL Gold and BREEAM Outstanding – believed to be a world first for all three standards. The site at 1 Regent Street, Cambridge is also set within a conservation area, with planners keen to retain the existing appearance.

Overcoming the planning challenges required forensic analysis of the energy and daylighting benefits of replacing the 97 mock Georgian windows. Passivhaus Planning Package (PHPP) analysis was used to demonstrate that overall carbon emissions from the building will be cut by more than 80 per cent over the next 100 years. The carbon savings amount to over 10,000kg CO2e/m2 over 100 years compared to a standard office refurbishment – cutting the equivalent of driving a fossil fuel car around the world over 27 times each year. The building is believed to be the largest EnerPHit certified office building in the UK and achieves 75 per cent lower heating demand compared to an average office, with airtightness around five times better than building regulations.

A wellbeing focus

The existing windows’ chunky sash bars blocked light so were replaced with triple glazed and recessed Passivhaus windows, using minimal contemporary framing. Light studies show a 60% improvement in the amount of glazing, nearly doubling the amount of natural daylight, and allowing light to filter into the building. The move also delivered much better thermal comfort for staff, who won’t have to experience draughts in winter or overheating in the summer.

35 per cent of the materials are bio-based using non-toxic materials to enhance health and wellbeing. Acoustically, a recycled newspaper spray coating to the concrete soffits helps absorb background sounds, making it easier to hear well and creating a calm workspace. The internal wall insulation is two layers – a cork and clay render and a wood-fibre board – rather than plastic foam.

To achieve the EnerPHit standard, mechanical ventilation heat recovery (MVHR) units are used to bring in a constant supply of fresh filtered air. The system allows heat from people and equipment to be recovered to cut energy costs and keep temperatures constant for thermal comfort. Although the designs were begun well before Covid, the excellent fresh air ventilation rates from the units are critical for maintaining healthy air quality.

A circular office

A circular economy approach ensured the retention and repurposing of materials, with new products designed for repair, refurbishment, reuse and disassembly. The building gained a BREEAM innovation credit through the contractor ISG who re-used lighting from another building refurbishment. This required the testing and re-warrantying of more than 350 LED lights – another example of an extraordinary measure taken to disrupt the typical construction industry approach, with most suppliers reluctant to give guarantees on products that are no longer new. The lifts were also retained, with the original manufacturer working hard to test, replace certain parts and re-warranty the lift. A desk recovered from the headquarters of Netflix was re-shaped to fit the new entrance space. The beautiful stone surface, damaged in the removal process, is repaired using the Japanese kintsugi visible repair method to celebrate the building’s philosophy. Leftover furniture in the building was diverted from landfill, avoiding wastage of 21,000kg of CO2, with 21,600kg of chairs, tables and storage cabinets donated to local communities.

Learning lessons

Given the urgent need to take action by every building owner, the Institute has developed a detailed case study to help organisations and students understand the many steps taken to achieve the approach. A soft landings approach to support users in occupancy and a building performance evaluation by the university will add further learnings to industry knowledge and help inspire others to make the building’s approach become the norm.

Wendy Bishop, Architype’s lead architect on the project, comments: “Given Entopia’s origins as a hub for communications, it is fitting that the building has come full circle and has been rejuvenated as a pioneering global example of sustainable retrofit that clearly demonstrates how to tackle the enormous retrofit challenge.”