In Dialogue: Designing with Mass Timber
As part of our “In Dialogue” series celebrating Women’s History Month, we sat down with Associates Kirsten Clemens and Margaret Sledge to discuss working with mass timber, practice and industry shifts, embodied carbon assessment, and more.
Mass timber has well documented environmental benefits — it’s a low carbon alternative to concrete or steel — and also offers biophilic benefits to promote occupant well-being. What are some of the other advantages to using mass timber?
Kirsten: Beyond the emotional appeal of mass timber, and of course its sustainable appeal, a lot has to do with speed of construction. When you work with a project team that is familiar with or open to the collaborative process, it can bring the project timeframe down when compared to steel and concrete buildings. Bringing the project to market faster helps clients start their ROI sooner and saves everyone money. Projects often require less crew members onsite and there can be lighter foundations as well, as the structure is lighter.
Margaret: On our current work at Greenhill School, speed of erection time was not a deal breaker but a positive benefit. One of the things that appealed to our client was the acoustic implications of using mass timber. The site is within an active school campus that borders a residential neighborhood to the north. Greenhill was excited to learn that the noise of erecting the structure would be less than with a similar steel or concrete structure.
We’re currently using cross-laminated timber at the Greenhill School Valdes STEM + Innovation Center in Dallas, Texas. Can you share a little about how the conversation around using CLT evolved?
Margaret: Greenhill started its selection process with an idea about a high-performance, sustainable building that would serve as a teaching tool for students. They wanted to think about designing the new STEM + Innovation Center in a way that looked to future while also capturing qualities of the more timeless architecture on its campus, including the presence of exposed wood structure and heavy timber.
As we were thinking about sustainability measures that would be unique to Greenhill’s specific condition, campus, history, and vision for the future, targeting embodied carbon goals and thinking about ways to push performance in that direction fit their conditions and also challenged our team to continue to advance our knowledge and expertise. When we introduced mass timber as an option early in the design process, the project team and clients gravitated toward it — it stood out as a priority and has become integral to project.
Our practice has a history of using mass timber products across a variety of scales and typologies — Ballard Library in Seattle, the Pocono Environmental Education Center, the Grand Teton Visitor Center, and residential projects around the country. Do you see a shift in the way our practice approaches working with mass timber now?
Kirsten: Looking at our history and where we are now, as well as the industry — there is a shift in the way we work with fabricators, suppliers, contractors, and structural engineers to come up with solutions. Not only is mass timber an aesthetic choice but often involves more layered reasons — speed to market, lighter foundation, and many more connections to choose from, for example.
Sometimes hybrid solutions can also make a lot of sense depending on the needs of the project, program, and region — it doesn’t always have to be an all or nothing thing. Some of our clients have had an interest in using mass timber for a long time; how do we help them begin to incorporate it into their vocabulary in a way that makes sense? Getting clients interested, sharing knowledge, and having open conversations that can help them make an informed decision is important.
Margaret: I see mass timber as part of larger conversation around embodied energy and the lifecycle of materials we select. The wood lobby has done a good job in marketing their products as a low carbon alternative — but if projects end up having to source materials from abroad and factor in associated transportation, you can end up negating the low carbon benefits of wood construction. Some are interested in mass timber as innovative without thinking about whether it’s really the best material for their specific project. So I think it is important to approach each project with that in mind — that there will be an ideal solution for each and if we can’t reach our 2030 Commitment embodied carbon goals with mass timber, there are other things we can do to do that’s best for both project and planet.
As mass timber use options and systems continue to evolve, what new opportunities do you see for our practice?
Kirsten: There’s an opportunity for us to take on creating a working system of embodied carbon assessment and development of objective criteria to help us measure how we continue to evolve. This is of the biggest things we can do, and this goes beyond mass timber.
How does mass timber use at Greenhill School factor into project lifespan and changes in use over time?
Margaret: Greenhill asked specifically for a flexible building that could grow as curriculum changed and be modified to fit evolving uses over time. That’s what we’re trying to accomplish for them: a building that they can move around, where the structure stays in place but within that, there’s a large amount of flexibility.
Kirsten: We have a confidential workplace client where we created an office environment within a space that was formerly a multi-story horse stable — buildings like these are revered but need a lot of love and support to creatively adapt for modern use. We expressed the structure to bring that warmth through and work off of it. Our projects have a high level of customization where we’re addressing specific needs for our clients, but also built-in flexibility that considers how they’ll grow and change. Timber structures often lend themselves to that potential because there’s a regular grid you want to express and flexibility within.