By now it’s a well-established fact that buildings can have negative impacts on the climate before they’re even occupied. In fact, nearly a third of the greenhouse gas emissions that come from the built environment—up to 12% of the earth’s total—stem from manufacturing, transporting, installing, and eventually disposing of building materials. The carbon emitted to produce the millions of tons of glass, steel, concrete, and masonry that make up our cities is “embodied” in these materials. Reducing those emissions while building the structures cities need to accommodate changing needs and growing economies is one of the greatest challenges facing architects today.

Preserving buildings is one way forward, but what to do when an existing building is no longer suitable to contemporary needs, even though its component materials are sound? KPF encountered this scenario at 81 Newgate Street in London, a hulking fortress of granite and Portland stone that once housed offices for British Telecom. Rather than raze the building, cart off the rubble, and start afresh, KPF opted to treat the existing building as a quarry from which to source materials, rearranging existing structural elements and façade pieces while adding new interventions where necessary. “A previous scheme for the site included demolition and new build, but we approached the project with the assumption of transformation,” explains John Bushell, KPF Principal. “The existing building is extremely robust and well-made, which was a great argument in favour of reuse and against demolition—saving a huge amount of carbon, construction time, and waste.” The resulting design preserved 76% of the existing building, saving 465 kilograms of embodied carbon dioxide per square meter (half of what a conventional building would produce), and created a new landmark for central London.

“Each adaptive reuse project is unique and requires a deep understanding of the original building, but there are common threads,” John points out. “One important element is that concrete codes were very generous for buildings of this period. Without the benefit of computational design, the structural engineers built in more redundancy than they needed. Plus, concrete hardens over time, so the structure of the building is stronger now than when it was designed. This meant that we could add additional load to the existing frame—allowing for some extension.” That extra strength enabled KPF’s design to carve a new covered walkway through the centre of the site and add new, stepped massing to the top of the building. These setbacks provide extensive terraces and a spacious rooftop as well as dramatic views of St. Paul’s Cathedral, from which the redesigned building takes its new name, Panorama St. Paul’s.

The existing building’s façade, clad in granite and cream white Portland stone, had very small windows that left interiors dark and claustrophobic while appearing heavy and unwelcoming from the outside. KPF’s solution, in collaboration with stone contractors Grants of Shoreditch, was to carefully disassemble the stone panels on the façade and rearrange them into new façade modules with larger windows and fluted terra cotta spandrels that break up the mass of stone, creating visual depth, transparency, and a sense of lightness. The new, high-performance façade panels are prefabricated and can be demounted and refurbished as needed. “The goal of KPF’s adaptive reuse projects,” says John, “is to preserve history whilst allowing for vigorous renewal.” Here the building’s bespoke, modern aesthetic is firmly rooted in its historical context: The rich grey-white Portland stone is the same cladding that Sir Christopher Wren selected for the nearby cathedral, creating a material echo that reverberates across centuries.

The new Panorama St. Paul’s is a 576,000-square-foot office destination with flexible workplaces, larger office floorplates, and plentiful outdoor spaces that accommodate how today’s leading corporations work. At every opportunity, office floors were provided with their own external terraces. The new, expansive roof terrace supports a restaurant, wildflower meadow, and access stairs that, with their striking city views, become a feature in their own right. Alongside attractive office space, the building will also include a gym, swimming pool, and ground-floor retail spaces for 24/7 activation. Abundant cycling infrastructure was another key component of the project, which features parking for 1,300 bicycles to encourage active travel.

In addition to cutting embodied carbon in half through its innovative material reuse strategy, and sending no construction waste to landfill, Panorama St. Paul’s is targeting BREEAM Outstanding, Wired score Platinum, and NABERS 5* Excellent rating. As an all-electric building, Panorama St. Paul’s is ready for the energy transition and will be net-zero once the local electricity grid is decarbonised. With whole-life carbon emissions of 371 kilograms per square meter, it will meet the aspirational targets for whole life carbon set by the Greater London Authority.

“Ultimately, a low-carbon development is the cumulative effect of many decisions, and not the result of one grand gesture,” says John. “We’re learning on every project and feeding that knowledge back into the design process.”