In this series, speakers from USGBC Northern California’s GreenerBuilder conference, held July 13, 2017, at the Zero Net Energy Center in San Leandro, share insights from their sessions. Interested in supporting GreenerBuilder 2018 as an event sponsor or exhibitor? Please contact Brenden McEneaney.
Building with mass timber is relatively new to the United States, and particularly to Northern California; the session served as an introduction to the material and basics of construction, set the context for the role of mass timber in sustainable design and high-performance buildings and presented lessons learned from an experienced developer.
The term "mass timber construction" or "tall wood construction" is different from light-wood frame, stick-frame or even heavy timber post-and-beam structures. Mass timber usually refers to timber products engineered for loads similar in strength to structural materials like concrete and steel. Fire and structural engineering methods for these materials have been well developed around the world in the last 20 years, and we are realizing the many benefits mass timber that allow us to build tall, with a lighter, natural, low-carbon and high-quality material.
There are several products in the mass timber family. Nail-laminated timber (NLT), glued-laminated timber (GLT), and cross-laminated timber (CLT) are some of the most common. Each product is engineered to provide strength in different ways, and the way we use them varies accordingly. CLT is particularly versatile, and it presents strong opportunities for Northern California.
Building with wood is an opportunity to realize complementary performance benefits contributing to environmental, social and economic goals at all scales.
The use of mass timber helps with our shift to renewable resources, necessary as part of large-scale climate adaptation and mitigation. Mass timber supports very efficient and high-performing envelopes, and the precision manufacturing process creates extremely airtight buildings that can support good passive strategies for high-quality and comfortable operation.
Economic benefits include off-site fabrication, making construction schedules shorter and limiting financing time. Wood is a lighter material compared to concrete, allowing for a reduction in the size of footings and an associated reduction in costs. In addition, mass timber often means smaller crews and simpler tools.
Aesthetically, the natural qualities of wood lead to increased occupant satisfaction. Humans are attracted to natural shapes, forms and textures, and wood is widely understood as a material that contributes to our sense of well-being in spaces and that can be a very healthy alternative to other finishes as an exposed surface on the interior.
Finally, mass timber is being used around the world to contribute to local and global climate action goals. It has a place in policy at all scales of governance as many jurisdictions recognize wood as an integral part of a low-carbon development, tying it directly to economic development, research initiatives and emissions goals. Local expertise with the material is growing, and many resources exist to support developers, designers and construction professionals.
Lessons from experience
The benefits of building with CLT in the United States is demonstrated by Lend Lease’s Redstone Arsenal hotel project in Huntsville, Alabama. Completed 37 percent faster than traditional steel frame construction, and first-cost neutral, this example was a success that is being replicated in support of positively disrupting traditional construction methods. Analysis indicates that this approach could be optimal in the current residential, hospitality and office market sectors for mid-rise buildings of between six and 12 stories.
Challenges in the industry include a limited supply of CLT within North America, limited industry experience, lack of testing data and explicit support in building codes. Although it is currently possible to overcome regulatory barriers, early adopters like Lend Lease are supporting fire, blast and seismic testing to demonstrate acceptable performance parameters to regulators and authorities. Moreover, new U.S suppliers of CLT are becoming available, and other mass timber products can be accessed through numerous suppliers across the country.
To accelerate adoption, emphasis on demonstrating that this approach is effective for mass market development is most important.
To learn more about mass timber, visit rethinkwood.com and download the Survey of International Tall Wood Buildings or the Nail Laminated Timber Design and Construction Guide. Check out the many learning opportunities, including a case study of Redstone Arsenal, through WoodWorks Education webinars.