With up to 40 percent of carbon emissions coming from the construction industry, the profession needs to find ways to adapt the type of buildings it designs, and fast. The default option for any project should be the adaptation and reuse of an existing building, which is one of the main demands of AJ’s RetroFirst campaign.
Our ongoing series strives to celebrate projects that save buildings from ruin or give them a whole new life.
Today we hear from Fred Pilbrow, Partner at Pilbrow & Partners, about how the company repaired the 1973 Brutalist Building in Kensington, while keeping the Boots store open.
Tell us about the project
The Kensington Building is a A mixed-use renovation project designed by Pilbrow & Partners on behalf of Ashby Capital. The building offers 11,974 square meters of office and retail space. Construction was completed in April 2022.
We started with a building from the seventies. Architecturally and urbanly, it had many shortcomings: its primitive concrete facades detracted from its historical location. Its orthogonal and brutal crowds eroded traditional street lines, and the empty, inactive facades at ground floor level created a hostile presence.
However, the building had positive qualities that allowed it to be successfully renovated. It had a regular and widely spaced structural grid, good floor-to-ceiling heights and high retail floor loads.
We stripped the building to its frame and then expanded the structure laterally to restore the building’s historic lines on Kensington High Street and Right Lane. We added three levels of accommodation above, which are set behind richly landscaped garden terraces.
The building is adjacent to High Street Kensington Tube Station. We created a new showroom to provide 24/7 access. These lanes are lined by a renovated Boots unit on Main Street and a walk of independent shops to the south.
What are the challenges of the current building?
Even with a modern building in 1973, the quality of the archival information presented a challenge to the renovation process. Our distinguished structural engineers, WSP, needed to be confident in the structure and construction of the original building to allow for its extension and reconfiguration. We searched archival sources (the Building Watch and London Metropolitan Archives) and supplemented the information with intrusive survey sampling on site.
Work on the site was closely associated with the archival drawings and we were able to proceed with the renovation, with confidence in the structural capacity and longevity of the retained superstructure.
Boots’ pharmacy license was dependent on the continuing trade and ISG, the prime contractor, sequencing the business to allow Boots’ ongoing business.
The aspects of the renovation that proved most successful were controversial and difficult to plan. We brought back the three new office floors from the restored facade of Wrights Lane. Here, offices face adjacent residential areas and the planners of the Royal Borough Council of Kensington and Chelsea initially resisted allowing the offices access to the landscaped terraces.
Working with Gillespies Landscape Architects, we proposed a 3m planting strip outside the office balconies to provide a visual barrier between the balcony and the facing residence. They also have limited balcony sizes, so large social gatherings will not be encouraged.
We have proven that providing offices with external access, as well as being good for luxury, also stimulated commercial tenants To pay for and maintain the landscape.
Has a demolition or partial demolition been considered?
We prefer renovation where the quality and character of the existing building allows. In this case, it immediately became clear that the robust and generous dimensions of the department store formed the natural core of a reimagined mixed-use building.
In addition to the embodied carbon benefits of repurposing existing infrastructure and superstructure, there were significant benefits to the construction program (less year of new construction) and reduced disruption with fewer deliveries associated with demolition and new construction.
To facilitate the creation of high-quality retail and office spaces, demolition elements were required. We constructed a walkway on the ground floor, a new steel siding core and demolished the original rooftop and roof slab, which had insufficient loads, all the way to the second floor slab.
Some items, such as the high-grade steel frame factory enclosure, contain relatively high carbon, which somewhat balances the savings of the retained structure. The total embodied carbon – 700 kg C02e/m² – is a very reliable figure, but falls short of the LETI target of 500 kgC02e/m².
Aside from retaining the original texture, what other aspects of your design would reduce the carbon footprint over the life of the building?
The building is designed for BREEAM Premium and WELL Gold certifications. The EPC B rating was calculated.
The building design reduces operational carbon by applying the Greater London Authority’s energy hierarchy: be light, be clean, be green, be visible.
Be Lean: Thermal-efficient facades improve the ratio of glazing to solid walls To give good daylight without unwanted solar gain. New elevations in white Roman brick and Portland stone provide deep undertones of interior glazing, aiding in negative shading. Good daylight even for deep and lower floors is achieved by wide ceiling heights.
Stay Clean: Ecosystems combine operational energy efficiency with high luxury standards. Opening panels on the facade allow for natural ventilation and mid-season mixed mode. calm The displacement system delivers generous amounts of air across the floor.
Be green: air-source heat pumps and photovoltaics to make a renewable contribution.
Be visible: The building integrates advanced sensors and controls. Unoccupied spaces are not cooled, ventilated or lit. Conversely, spaces with higher occupancy levels are provided with additional ventilation and cooling.
Did the planners endorse the proposals?
The planners were very supportive of the proposals. Three aspects have been identified for particular support: the scheme improves the development potential of a well-connected site, enhances the public realm by introducing new permeability for the Kensington High Street tube station and increasing the proportion of the active facade, and the quality of the new building design.
The site is sensitive. It is surrounded on three sides by conservation areas and to the west by the Grade II listed Derry and Toms Store and behind the Grade II listed Barkers Department Stores. We discovered how renovation should relate to these wonderful neighbors through their powerful Portland stone elevations and underglazed bronze finishes. The elevations of the white pointed Roman brick and stone are developed. It relates tonally to Portland stone, but the materiality of the brick establishes a submissive presence (and relationship with the mansion’s brick blocks to the west of the site).
Is your approach to retrofitting and the way you talk about it with customers changing, especially given the increased focus on the climate emergency?
Retrofitting is often the right answer and we hope the Kensington Building demonstrates that we have the expertise to renovate buildings that you will be interested in and committed to.
However, we don’t think retrofitting is the right answer in every circumstance. When existing buildings are compromised in their design, structure or construction, their retention can have very poor long-term results in terms of building function and sustainability.
Therefore, our approach is context driven and in no way will we assume knowing the correct answer without a thorough understanding of the existing building constraints and opportunities.