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Sustainable Design in Structural Engineering
By Jacob Loew & Galen Reed
Image: The Adelaide Pointe Mixed-Use Building is being engineered using mass timber. Rendering by Architektura.
For over 60 years, Progressive AE has been committed to innovative and sustainable designs that benefit our clients and communities. In this blog series leading up to Earth Day, we’ll share knowledge and best practices we’ve learned along the way.
In our last blog we discussed the importance of balancing operational and embodied carbon emissions in order to reach the firm’s AIA 2030 goal of net-zero. As structural engineers, we are most interested in embodied carbon, which is carbon produced during the manufacture and shipment of building materials like steel and concrete.
Aiming for Elegance
Our team puts intention behind material choices, specifications, and efficient designs in order to reduce overall tonnage (saving both cost AND waste). We like to call this “aiming for elegance” – you can throw a lot of blocky steel at a project and it will stand, or can you find an elegant solution that neatly solves the problem and is inherently efficient.
Another way we approach sustainability is using local manufacturers and focusing designs around materials that can be sourced near the project. This avoids unnecessary carbon emissions due to transportation. An added benefit is that local contractors are accustomed to working with the materials.
One of the biggest selling points for steel is that it’s entirely recyclable. In fact, upwards of 90% of the steel used today is recycled. Historically, the recycling process also contributed to a gradual increase in the strength of the stock of steel available, allowing us to use less steel in our buildings today than would have been required without the heavy use of recycled material in steel production. Some United States steel plants are starting to operate on solar and wind energy, but the processing and production of steel still accounts for about 6-7% of the world’s greenhouse gas emissions and the industry has a way to go in that regard.
At times we do have contractors and clients inquire about steel alternatives. One recent example was a request to use carbon fiber rebar. Our team always researches and discusses new materials to ensure the alternative will not compromise structural design and is proven to be better for the environment. With any new material, we also explore these positives and negatives with our clients.
Concrete is a large contributor to embodied carbon due to the manufacturing process, but the industry is changing. One example in Michigan is that most plants have transitioned to type 1L cement which has higher limestone content and lower carbon footprint.
Our specifications for concrete are continually reviewed to include items like Type 1L cement and many of the other industry standard practices such as fly ash percentages.
Mass timber is not a new product but has recently gained immense traction as a highly sustainable material. On the threshold of exploding onto the marketplace, mass timber includes engineered wood products that are extremely strong, fire resistant, and renewable. Although initially most cost effective due to availability in the Pacific Northwest, there is growing client demand and environmental need for a material like this. Manufacturing facilities are being built and brought online across the United States making it far more accessible. Not only does wood take less energy to produce, it can be farmed and grown relatively quickly and engineered in large quantities.
Mass timber has opened possibilities across many markets and can even be used in high-rises. Right now, the tallest project in the world is Ascent, a 25-story apartment complex in Milwaukee, Wisconsin. The Portland, Oregon airport is currently installing a 9-acre mass timber roof over the main terminal.
The construction industry will need to learn how to work with this relatively new material, and it hasn’t become widely available yet, so transportation is a challenge for some projects. But our team is optimistic about the possibilities. From a structural perspective it has good strength properties and its lightweight nature makes it an excellent choice for high seismic areas and sites with poor soils.
Building for Resilience
A word that often goes hand-in-hand with sustainability is resilience. As structural engineers, this is paramount to our designs and failure isn’t an option. We stay up to date on local building codes in each state to ensure our buildings stand the test of time against potential climate events. A project in Florida needs to withstand increasing hurricane level winds, while one in California may need particular design considerations for wildfires. As we adapt to a changing climate, we must ensure our projects are ready to withstand the future, whatever it may hold.
One of our recent projects that prioritized sustainability is the Bay Area Transportation Authority facility in Traverse City. We were intentional about optimizing our material use and showed the client a number of iterations that could minimize the total steel tonnage and thus both the cost and environmental impact. Ultimately, we were able to find a solution with the client that met the needs of the space and reduced the initial concept’s steel tonnage by over 30%.
Recently we have had the opportunity to design and implement mass timber on a handful of projects. On one project, we used a cross-laminated timber deck and glulam beams and columns to provide a statement space for a workplace client that brings nature indoors while providing the above referenced benefits of mass timber. We’re also working on Adelaide Pointe, a mixed-use project utilizing mass timber super structure. That project is benefitting from the sales appeal of the biophilic nature of mass timber and the overall weight reduction on a site with relatively poor soils.
Our team is always looking at ways to reduce our environmental impact. As we learn about new methods and materials, we educate each other and our clients. Contact us if you’d like to talk with one of our design experts about your project.