Over the past few months, there has been a steady stream of conversation and research around the office related to the subject of mass timber and its application in building design and construction. The stars (and wood!) aligned in mid-July when our own Director of Sustainable Design and DC CREW EDU committee member, Holly Lennihan, joined The National Building Museum’s Timber City Exhibit, Forestry experts and other industry representatives for a panel discussion on the topic as a part of CREW DC’s “Innovation” education series.
Following the program, we sat down with Holly to discuss this growing trend, its application, and the design implications of using mass timber.
Why was mass timber a timely fit for CREW DC’s “Innovation” series?
The idea for the program originally grew out of conversations I was having with people in our office. This trend represents an exciting new way to use wood in our industry, and not many firms have experience designing and building with mass timber therefore our list of potential panelists was limited. However, through CREW EDU committee members, we were able to connect with both Melissa Jenkins of the U.S. Forest Service and Nadine Block of the Sustainable Forestry Initiative. Lauren Wingo, structural engineer at Arup, joined the team on the heels of a presentation Arup gave on mass timber to the Hickok Cole office. She was an integral part of their presentation, and we knew she would bring a lot of value to the program.
What innovations and advancements have been made to make building with wood in urban areas safer than the approach has been in the past?
During the panel, Melissa spoke specifically about the extensive safety testing. As I understand it, when a Cross Laminated Timber column or beam burns, a fascinating thing happens where the outside layer chars and actually insulates the inside. So, counter to what you would think, the burned exterior becomes the protection for the interior. According to Melissa, everyone who watched the fire test was stunned by how well the timber performed.
In addressing seismic issues, Cross Laminated Timber is a surprisingly effective structural system due to the process of laminating in two different directions. This technique results in ductile behavior, giving the structure flexibility and allowing for energy dissipation because the timbers can move against one another.
“Why not strengthen the wood production industry through investment in mass timber material? It supports domestic manufacturing while both helping the environment and contributing to beautiful interior design. I predict we will even see productivity gains in people who work in spaces where the wood structure is visible. To me, it resonates across the triple bottom line—a win-win-win for people, planet and profits.”
– Holly Lennihan
How is Cross Laminated Timber addressing established North American building codes that bar against the use of mass timber in high-rise development?
The 2015 International Building Code (IBC) allows for Cross Laminated Timber, but it has not yet been adopted by DC or Virginia. There are, however, alternate paths for incorporating mass timber in the meantime while complying with current codes. Lauren shared an example where Arup was able to use mass timber in their approach to Washington Latin Public Charter School’s new gymnasium; they walked the Department of Consumer and Regulatory Affairs (DCRA) through a process to show them how Cross Laminated Timber can meet fire and structural requirements for the code. This was, of course, aided by the fact that the material is included in future versions of the IBC.
Once there is a developer on board that understands that building with this material has valid economic rationale, while also giving them an edge in terms of their product offering, we anticipate others will follow. Hines has already successfully delivered a mass timber high-rise office tower in Minneapolis. At Hickok Cole, we’re excited about the opportunity to work alongside developers who want to be at the forefront of this kind of innovative work.
Are there sustainable or aesthetic benefits to building with wood over other materials?
From an aesthetic and wellness angle, there are benefits to taking a biophilic, human-centered approach to design. We are finding more and more connections between natural building materials and productivity, health and wellness. Plus, exposing the natural wood makes for a beautiful interior.
Nadine did a really good job of explaining the role of culling to maintain healthy forests. This necessary clearing results in a supply of timber that can be used throughout the built environment. Others are using wood from forests that have been decimated by the Mountain Pine Beetle, an epidemic brought on by climate change that is currently ravaging the West. Both approaches are helping to keep forests healthy and repurpose excess wood into a useful building material.
Are there financial benefits for developers that choose to go the mass timber route?
I think people that have used it successfully point to its ease of use and the resulting increased speed of construction. Anytime you can cut down on construction time, you are going to have a net gain in terms of expenditure and budget. Additionally, the fact that it’s a lighter weight material means a decrease in foundation costs.
As a designer and architect specializing in sustainability, why do you think mass timber is something DC—and the rest of the country—should be focused on right now?
For one thing, DC’s incredibly committed to sustainability. I think design professionals like myself feel that if there’s one place mass timber could enter the market, it’s here. We are looking for clients – whether it’s a developer or a mission-driven non-profit – to see the benefits of Cross Laminated Timber and be an agent of change.
However, we do have to be realistic. I think there are design constraints which could make it difficult to convince a central business district developer who wants to do a concrete and steel building to go the mass timber route. On the other hand, people may find new ways to use it. I’m both pragmatic and idealistic. I believe the use of mass timber will ultimately result in a better building, but it doesn’t have to be an all or nothing approach.
Special thanks to the DC CREW EDU committee members and to the following expert panelists who contributed to the “Timberrrr! A New Look at Wood Construction” program:
- Melissa Jenkins, Natural Resources Specialist, Cooperative Forestry (Wood Innovation), U.S. Forest Service
- Nadine Block, Chief Operating Officer and Senior VP Public Affairs, Sustainable Forestry Initiative
- Lauren Wingo, Structural Engineer, Arup
Want to learn more about mass timber’s use in building design and construction? Check out these additional resources:
- ReThink Wood
- Council for Tall Buildings and Urban Habitat, Tall Timber Audit
- S.538 Timber Innovation Act of 2017
- “New federal act could give mass timber a big boost,” The Architects Newspaper