A blueprint for cutting carbon in construction

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By Frank JossiBridgeTower Media Newswires

Architects and builders working to reduce carbon have discovered the challenge remains enormous.

Every material in the construction process involves carbon in its creation. Building anything generates carbon emissions, from trucks driving materials to a site to the power consumed to create those materials. Yet architects have been working on approaches using a mix of tools that help find suppliers and monitor outcomes, making decarbonization more achievable.

In November, the Minnesota chapter of the American Institute of Architects’ annual conference featured a session on best practices for decarbonization projects. Speakers broke down their approach and the challenges they had to overcome to get to near-net zero projects.

A national leader in sustainability, Douglas Pierce oversees Perkins&Will’s resilience and regeneration initiative and has been part of 25 certified sustainable projects, including Great River Energy’s headquarters in Maple Grove, Minnesota. Before delving into the details, Pierce suggested that architects and builders must understand each other’s roles.

“To decarbonize, we need to all become better interdisciplinary teammates and understand each other’s disciplines better as we go along,” he said.

Every project involves embodied carbon from the production of materials and operational carbon created by building heating, cooling, lighting and, potentially, transportation involving employees, Pierce said.

Embodied carbon has to be measured in every part of a project. Architects should consider the carbon count of building products, construction activity, and the heating and cooling of buildings over 60 years, including the impact of reuse or demolition.

Pierce said a building constructed this year will see 49% of carbon emissions from embodied carbon if the electricity grid becomes carbon-free by 2050. “As the grid gets cleaner, more carbon is attributable to embodied carbon,” he said.

Information sources exist on embodied carbon to help guide architects, including Perkins&Will research reports, in collaboration with the Healthy Building Network, focusing on low-carbon gypsum drywall, flooring, and insulation and plastics reduction. Another resource is the Athena Sustainable Materials Institute, which provides free software programs allowing professionals to estimate the carbon impact of various products.

Embodied carbon adds up. Perkins&Will did a study of 97 of its built projects, from labs to offices. Pierce said the total embodied carbon was 790,000 tons, enough to operate 103,000 homes annually.

The most embodied carbon, 44%, came from metal and reinforcing steel, with 36% from concrete. Materials under 10% included openings, glazing and thermal and moisture protection. As an experiment, researchers redid building specifications to require more sustainable materials such as greener concrete and reduced embodied carbon anywhere from 10% to 40%, he said.

Pierce offered four examples of projects he worked on that reduced embodied carbon, including the Perkins&Will office at the IDS Center. Designed in 2016, the office has almost no carpet, no ceiling tiles, and has plywood components. Shelving and other objects from the firm’s former office were repurposed, he said.

For Avivo’s headquarters in Minneapolis, Perkins&Will stripped and reused a concrete building for the chemical dependency, career services and mental health provider. “It was cheaper to reuse the frame than demo the frame and the basement,” Pierce said. Perkins&Will is using mass timber to add two stories to the building, rather than one, as the original plan called for. He said mass timber, lighter than concrete, allowed for the extra floor.

Pierce spoke about other projects using fly ash concrete and designs to reduce square footage. The architect suggested measuring carbon with EPIC, a free software tool.

One emerging issue in creating more low-carbon buildings is the impact of climate change. Heavier snowfalls and higher wind loads could require more materials to construct firmer structures. “It’s a sort of interesting dichotomy,” he said.

Kyle Thompson, a lead engineer at Michaud Cooley Erickson, spoke about bringing clients, facilities staff, architects and contractors together before building projects with low-carbon goals. Getting buy-in remains a critical element of successful projects, he said.

Issues inevitably arise as facilities work with new ways of heating and cooling. Thompson said he worked on a library project where air source heat pumps produced a fair bit of moisture, as they usually do. The library facilities staff didn’t understand that could be a problem, he said, but his firm found a simple solution in directing water to drains.

Speaking to facilities staff about how new technology operates differently should be included in projects. “They don’t have to be at every design meeting, but conversations with them should be had,” Thompson said.

Jeff Anderson, an aviation practice area lead for Meyer Borgman Johnson (MBJ), addressed “Scope 3” emissions. Scope 3, sometimes called “value emissions,” consists of indirect greenhouse gas emissions resulting from activities not controlled by clients but influenced by them.

Anderson suggested the audience consult Life Cycle Assessment by Kathrina Simonen, which is a “lesson in things you think you know that you don’t.”

Whole building lifecycle assessments offer information on selecting appropriate materials for projects, he said. However, the data should be parsed to target the most significant impacts on greenhouse gas emissions, citing the Pareto Principle, where 20% of effort creates 80% of results.

Anderson said that in one project he engineered, he saw challenges with concrete and thermal moisture. He first set criteria for what he wanted in concrete and then called suppliers. He shares specifications with suppliers before bids go out to see if they can provide sustainable materials and environmental product declarations (EPD) to prove it.

Anderson gives the chosen supplier a list of questions, such as where the concrete was the source material and how it traveled to the company’s plant. Before use in the project, EPD-labeled concrete mixes from a Twin Cities supplier were tested.

The results, he said, were impressive. The project exceeded the reduction in carbon from the North Central average for concrete that the project team had sought. It’s a win.

“Be a little bit more incremental rather than trying to swing for that home run right off the plate,” Anderson said. “Let’s make some gains. Let’s see how they go and make more gains later.”