Material Innovation Case Studies
The Carbon Issue

Our buildings can have deleterious effects on the climate long before they’re even occupied. In fact, nearly a third of the climate emissions that come from the built environment—up to 12% of the earth’s total carbon emissions—stem from manufacturing, transporting, installing, and eventually disposing of building materials. Reducing the carbon that’s embodied in the glass, steel, concrete, and masonry that make up our cities is a major challenge to reaching global climate goals, and it’s one that requires architects to think deeply and critically about the building materials we use and their lifecycle.

Note:

This article originally appeared in the spring 2024 issue of KPF Review. View all of the accompanying videos here.

Cities around the world need new buildings to accommodate urbanizing populations and growing economies. The processing of raw materials required for all of this development produces a great deal of carbon emissions, accounting for 40–60% of a building’s emissions during the first 10 years of its lifespan, but there are design solutions to mitigate them.

For new buildings and buildings with new components, replacing materials with large carbon footprints, such as concrete, steel, or aluminum, with low-carbon alternatives, such as low-carbon cement, mass timber, and recycled materials reduces climate impacts. Some materials, like timber, have an even higher reduction capacity, as they sequester carbon from the atmosphere during growth that is later stored in the building.

When possible, to reduce waste and minimize embodied carbon, KPF pursues a “reuse and retrofit first” strategy. Our firm has been a leader in the field of adaptive reuse since our very first project, converting an armory to studio and office space for ABC, back in 1978. Since then, we’ve developed innovative approaches to reusing existing structures, avoiding teardowns while adding needed density, adapting to new uses, and preserving historic structures. In addition to reusing whole buildings, we’ve used building materials salvaged from demolition projects in new ways, reducing waste and creating historical continuity and character in the urban fabric.

For KPF, using these low-carbon materials and repurposing buildings are opportunities to explore new ground architecturally, and develop designs that make our cities more dynamic, livable, and sustainable.

The exterior of the ABC Armory. Credit: Peter Aaron/ ESTO.

Burrard Exchange

Vancouver, Canada

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Burrard Exchange is a loft-like, biophilic office tower that, together with its surrounding public space interventions, seeks to reinvigorate the prominent Bentall Centre in Vancouver, Canada. While complementary to the site, the building departs from its context in select ways, most notably in its use of mass timber as a key structural element and primary aesthetic motif.

As a building material, timber has the capacity to be not only carbon neutral, but carbon negative—actually taking more carbon dioxide out of the atmosphere than it emits. During timber’s growth cycle, trees absorb carbon dioxide; when they are harvested and transformed into mass timber components that can be locked away in a building, the carbon absorbed by those trees is sequestered.

Credit: WAX.
Mechanical systems are stowed above the timber girders, allowing the exposed wood’s materiality and texture to take center stage.

In the case of Burrard Exchange, timber is also a hyper-local material, with British Columbia being one of the world’s largest exporters of wood products. Vancouver has thus been at the leading edge of global cities in adopting building codes that facilitate tall timber buildings.

Timber presents several challenges, including strict building and fire codes, as well as the design challenge of being an unyielding material, disallowing eccentricities and curves. The KPF team innovatively synthesized the current local code with variances based on previously approved solutions and hybridized timber and concrete for the project’s upper 14 floors, using concrete for the columns and timber for the purlins, girders, and slabs. The design elegantly carves loggias and terraces into the grid necessitated by the timber frame system, creating an office tower that is at once rational and exciting.

Panorama St. Paul’s

London, UK

Sited in a prominent position adjacent to St. Paul’s Cathedral, 81 Newgate Street is a well-located but outdated office building that presented an ideal opportunity for thoughtful adaptive reuse.

KPF’s redesign carves a new covered walkway through the center of the site and adds a terrace to the top of the building to provide views of the iconic cathedral, from which the redesigned building takes its new name, Panorama St. Paul’s.

Before (credit: Richard Leeney Photography) and after (credit: Uniform) of Panorama St. Paul’s.

As a part of our sustainability strategy, the KPF team recognized the value of the Portland stone and granite that make up the existing building and chose to view the old office as a quarry. The new façades are a completely rearranged assemblage of the stone from the original exterior combined with harmonious terra cotta to create a modern aesthetic that remains rooted in the building’s local context.

The updated façade of Panorama St. Paul’s incorporates pieces of Portland stone repurposed from the existing building, keeping carbon out of the atmosphere and waste out of the landfill.

The rich gray-white Portland stone is the same cladding that Sir Christopher Wren selected for the nearby cathedral, creating a material echo that reverberates across centuries. By reusing existing materials, KPF cut the project’s carbon footprint in half compared to a full  demolition and rebuild, ultimately achieving an embodied carbon savings of 465 kilograms of carbon dioxide per square meter.

Additional sustainability measures include a net-zero operational carbon strategy, modular construction, a zero waste-to-landfill plan, extensive plantings, rainwater attenuation, and thermally comfortable adaptive environments. Panorama St. Paul’s is expected to achieve a BREEAM Outstanding rating and WiredScore Platinum.

17xM

Washington D.C., USA

Concrete is one of the most important building materials in the world. Unfortunately, it’s also among the worst for the planet. The production of Portland cement, the main ingredient in concrete, accounts for nearly 8% of global carbon emissions. Because of concrete’s omnipresence and its high environmental cost, building with lower-carbon alternatives and analyzing the carbon intensiveness of the concrete mixes used in our projects is a crucial component of our work to decarbonize the built environment.

17xM, a new office building KPF designed in Washington, D.C., is part of a research effort we have undertaken alongside our engineering partners at Arup to study embodied carbon in buildings. During construction, low-carbon cement was used for the building’s post-tensioned concrete floor slabs and concrete pillars. By replacing 20% of the Portland cement in the concrete mix with a combination of fly ash and slag, both industrial byproducts, as well as CarbonCure, a cement product made with mineralized carbon that’s captured from the atmosphere, this material offered a reduced climate impact that was widely available and price-competitive.

Credit: Visualhouse for Skanska

Because 17xM’s concrete structure is responsible for the vast majority of its embodied carbon footprint, the team found that by simply specifying low-carbon cement, they reduced the project’s overall embodied carbon footprint by 15% (over 1,500 tons) without making any design changes or adding costs for the client. The use of post-tensioned floorplates further reduced the building’s structural volume and weight, providing additional carbon savings.

Using concrete with 20% less cement than standard mixes cut embodied carbon emissions across 17xM’s structure by 15%.

The design for 17xM innovates on the typical D.C. office block by utilizing a dynamic form to dramatically increase the number of perimeter offices on each floor, while an articulated façade maximizes views. To achieve LEED Gold, the façade features a dynamic interplay of horizontal cells and vertical sun-screens, both optimized to maximize the insulating value of the wall, daylight penetration for offices, and solar control. Other sustainable components include a green roof to assist in stormwater control, high efficiency MEP systems, and local, recycled, and natural construction materials.

17xM topped out. Credit: Royce Douglas / Tectonic Photo.