28 jan 20  | Architect Magazine

The Pathway to Net Zero Carbon Buildings

By Dr. Chris Drew

Adrian Smith + Gordon Gill Architecture, the National Ready Mixed Concrete Association, and other partners are testing lower- and even negative-carbon concrete solutions.

Architects and engineers play a key role in building modern society—providing shelter and infrastructure to support our quality of life. But this quality of life comes with significant environmental burdens. According to the Global Alliance for Buildings and Construction, the built environment accounts for 39% of global CO2 emissions. Reducing and eventually eliminating these emissions is a significant component in any strategy to address climate change.

Building operations such as air conditioning and lighting are responsible for 28% of a building’s greenhouse gas (GHG) emissions. Through improved technology, more stringent building codes, and cleaner energy grids, we are making significant progress towards net zero energy buildings. Although we still have work to do to make all buildings net zero, we know how to get there.

The other part of the equation is embodied carbon—the GHG emissions associated with building products and construction. Today’s built environment relies on modern building materials including aluminum, concrete, glass, and steel, among others. Even wood, recently touted as the answer to reducing embodied carbon, comes with its own burdens—ensuring sustainable sourcing remains a challenge.

There is one building material that is used in every building we design: concrete. Whether a building’s structural system is concrete frame, steel frame, mass timber or other system, concrete comprises a significant portion of the structure, as in foundations, shear walls, and floors, and thus a significant portion of the embodied-carbon impacts. And of all the construction materials, design professionals have the greatest influence over concrete.

Project specifications written by structural engineers typically do not promote concrete innovation. Limitations on the use of cement substitutes and prescriptive requirements on minimum cement content drive up the carbon footprint of concrete unnecessarily. Many concrete producers and contractors are eager to provide concrete with lower impacts but limitations within specifications simply doesn’t permit it.

What has become abundantly clear is that it will take a collaborative effort between the design community and product manufacturing community to get to zero carbon. That’s why Adrian Smith + Gordon Gill Architecture (AS+GG) has embarked upon a concrete research project to develop a pathway to net zero carbon buildings. We’ve partnered with the National Ready Mixed Concrete Association, Ozinga Brothers (a concrete producer in Chicago), and host of materials and technology providers to develop concrete mixes with low, zero or even negative carbon footprints.
We plan to combine a variety of innovations including carbon capture technologies from CarbonCure, Solidia, and Blue Planet; cement substitutes such as fly ash, slag, and ground glass; and geopolymer concretes (concrete without Portland cement); among others. Our plan is to develop mixes for specific applications such as foundations, slabs, columns, and pre-cast elements, all of which have different performance criteria for strength, stiffness, and so forth. Some may have a low carbon footprint, others may have negative carbon footprint and sequester carbon.

Ultimately, we want to put what we learn into practice by designing and building a project using the low, zero, negative carbon concrete mixes we develop. We plan to publish our findings to share the successes and challenges and will write a guide specification that encourages these innovations. What makes this initiative different is that it encourages cooperation between design professionals and product manufacturers: The pathway to net zero carbon buildings.