In large cities such as Paris, London, and New York, the needs of office tenants have evolved. The prime, transit-connected sites in these cities are often occupied by aging building stock with limited access to natural light, views to the outdoors, and fresh air, driving workers into less-than-fulfilling—or even unhealthy—work environments.

Note

This article originally appeared in the spring 2023 issue of KPF Review. Watch the accompanying video here.

Rejuvenating a building with a new façade offers the opportunity to infuse aging workplaces with upgrades that can attract new populations while reusing the structural bones and embodied carbon of these well-located assets, many of which are now overbuilt according to local zoning laws. While each project poses a fresh challenge, this strategy ensures that we can preserve the environmental and economic value of older buildings while reducing the carbon impact of demolition and construction. The results speak for themselves: our aesthetic and environmental design revitalizations have attracted world-class tenants and dramatically driven real estate values.

La Défense, Paris

In the early 2000s, KPF’s repositioning work in France’s La Défense business district provided valuable lessons that we have applied to later projects. Located on a prominent site near the Neuilly Bridge, Tour First, one of France’s first skyscrapers at 40 stories tall, was conceived as three identical wings around a central core. Originally completed in the 1970s by designer Pierre Dufau, KPF and Associate Architect Saubot-Rouit Associés (SRA) redesigned the tower forty years later to retain the integrity of the original structure while vastly improving environmental performance.

Before (left), proposed (center), and realized transformation (right, credit: Hudton + Crow) of Tour First.

One of the prevailing characteristics of KPF’s design is the breaking down of the “wall effect” of the existing tower by cutting and stepping the wings in a counterclockwise direction and consequently opening interiors to natural light and views across the city. To achieve this, the original tower was raised by 10 stories, and the three wings were reconceived at variable heights, giving the tower’s form a dynamism that it previously lacked. Although 10% larger than the former tower, KPF’s retrofit meaningfully reduced energy consumption and reduced the tower’s CO2 footprint by 50% in comparison to the original tower.

A double skin “passive” breathing façade with special solar coating is integral to this environmental strategy, effectively “wrapping” around the textured single skin made up of high-performance, double-glazed units with folded aluminum spandrels. This design move reinforces the graceful twist of the building even further while responding to climatic and acoustic constraints. Upon reopening, Tour First was the largest fully HQE-certified office tower in France.

Close up view of Tour First’s facade, with views of the Eiffel Tower in the background.

Building on this experience, KPF and SRA teamed up once again in 2013 to kick off the refurbishment of a neighboring project, Window La Défense. The client, Groupama, decided to preserve the existing 1982 structure due to its prior success and good structural condition. KPF’s design recycled the existing base and gave it a new cladding system to enhance the office building’s presence in the major business district, also extending the existing atria and adding new amenity spaces.

Before image credit: Jean-Marc Besacier. After image credit: Hufton + Crow.

The two atria, which existed in the original building in plan but have been extended in elevation, improve natural light penetration into the heart of the building and enhance horizontal and vertical circulation throughout. Seizing the dramatic nature of its location, Window enters into theatrical dialogue with its surroundings by imagining the esplanade as a theater audience, its iconic neighbor, the Grande Arche, as a proscenium, and Window, with its rippled glass façade, as a stage curtain, improving the public face of the building while increasing wellness for office tenants.

Credit: Hufton + Crow.

The City of London

Located opposite St Paul’s Cathedral, the Panorama St. Paul’s development exceeds ambitious environmental requirements set by the City of London, demonstrating a path for the decarbonization of existing urban areas. Originally completed in the 1980s as the headquarters for British Telecom, KPF’s design transforms the outdated office block into a sustainable, mixed-use building and a new destination in a key site on London’s Culture Mile.

Previous schemes for the site included demolition, but KPF recognized that reusing the existing building would save a huge amount of carbon, construction time, and waste. The concrete frame was robust and over-engineered, allowing for the additional loading caused by extension.

Before image credit: Miller Hare. After rendering credit: Uniform.

Still, the existing building presented a number of challenges. The façade needed to be opened up to incorporate mixed-mode ventilation, increase access to daylight on office floors, and improve the relationship to the street through increased transparency. KPF saw the building as a quarry, removing original high-quality Portland Stone and granite and reusing 3,800 m2 of refinished stone with harmonious materials such as terra cotta, in an entirely new, high-performance façade.

Facade transformation process of Panorama St. Paul’s, with the original condition on the left and the reclad, high-performance product on the right.

Beyond this reskinning, the existing building had a low net-to-gross floor area, an inefficient internal atrium, and cores that need to be replaced and updated. More than 70% of the original structure has been retained, with new lift cores inserted into the partially filled atrium. Three new full-height slot atria, topped by skylights, announce principal entrances and define internal circulation space and public routes at ground level.

The overall material reuse reduces embodied carbon by 280 kgCO2e/m2, bringing the total lifecycle carbon of the project below 650 kgCO2e/m2; a 45% reduction over typical new construction office buildings in London.

Panorama’s new envelope reduces conditioning loads and integrates operable components for passive ventilation cooling in all office floors. Passive design is most critical in the façade atriums, which operate as open spaces in milder months, bringing daylight deeper into the floorplate, and rely on thermal mass and solar design to reduce energy use during the rest of the year. Designed for resilience and wellbeing, the building’s roof integrates photovoltaic panels with a fully planted terrace that controls stormwater, reduces urban heat island effect, and provides a publicly accessible open space in the City.

By transforming a monolithic and introverted single-use block into a welcoming and permeable mixed-use building, this retrofit creates an exciting destination on an important site. The completed building will address occupants’ needs and enhance the City’s public realm. The project is the first of a new generation of net zero carbon enabled office developments in London.

Midtown Manhattan

At 660 Fifth Avenue, KPF undertook a full recladding of a prominent 1950s office building that had been recently acquired by Brookfield Properties. With a very early version of a semi-unitized curtain wall, the original façade featured units with punched aluminum panels on the bottom and a single glass pane on top—lightweight and inconsequential in terms of structure, but low performing environmentally. The design team and consultants quickly understood that a full reskinning would be the best option to upgrade this aging building for today’s market.

Before (left) and after (right, credit: Hayes Davidson) of 660 Fifth Avenue.

When upgrading older office buildings, low floor-to-floor heights are a common challenge. At 11 feet, 660 Fifth Avenue’s floor-to-floor heights were significantly lower than the standard for today’s typical Class-A office buildings, which often measure 13, 14, or even 15 feet high. The original structure’s tight column spacing at the perimeter posed an additional challenge. By opening up the façade completely to introduce new units spanning column to column, the team was able to change what could be perceived as disadvantages into an opportunity—allowing the structure to virtually disappear alongside generous open views of Fifth Avenue and Central Park. Additionally, because the building was constructed before the passage of New York City’s zoning law, its GFA was significantly overbuilt. To maximize this area, the KPF team puzzled together a number of double-height spaces and incorporated new terraces at multiple levels of the building, offering outdoor space on three sides, including along Fifth Avenue.

The decision to reclad with the largest single-pane units ever used on an office development in New York City not only made sense from an aesthetic standpoint but also created efficiencies in construction, logistics, and structural detailing. The typical jumbo glass panel comes off the production line measuring 19 feet wide by 11 feet tall, which for this project, meant fabricators could use a single cut and create minimal waste when producing each panel. Situated inside a four-sided shadowbox, these panels were designed to span the full width between columns and the full height between floors, allowing plentiful daylight penetration to the interior spaces and tripling the window area for tenants compared to the original structure. Along with mechanical upgrades to optimize high-efficiency heating and air systems and bring in greater quantities of fresh air, these moves maximize occupant comfort and reduce energy consumption.

Credit: Raimund Koch.

During construction, without the capacity or space to lay down façade panels for install, the team orchestrated a careful sequence—trucking the finished panels from Long Island to the site, then directly loading from the trucks and onto the building with the crane. This efficiency was made possible by the structure’s reuse, as there were no competing structural demands on the crane’s usage. This opportunity, along with the existing steel moment frame’s capacity, helped make the install of these mega façade panels feasible. As a result, and despite their size, the panels were installed at the same rate as a standard five-foot-wide curtain wall unit, speeding the rate of install by almost four times.

One of the key challenges of any adaptive reuse project is to uncover what we don’t know—about the original building and the structure’s possibilities. What is the most impactful design intervention when a building no longer serves its community’s needs? While there is no single answer to this question, clever façade interventions can infuse older buildings with new promise, preserving embodied carbon in the elements that still deliver value and upgrading features to meet heightened standards for the future.