How Green is Mass Timber?

How green is mass timber in practice today? How does it compare to concrete and steel? What needs to happen for mass timber to be truly sustainable?

Moderator: Mark Wishnie, Executive Director, Timberland Investment Group, BTG Pactual

Breakout Topic:
Mass Timber Construction as a Circular Economy Solution - Challenges and Opportunities
Elaine Oneil, Director of Science and Sustainability, CORRIM
George Berghorn, Asst. Professor Construction Management Michigan State University

-In this panel presentation, we explore the forest to building construction to use and reuse life cycle of mass timber construction products like cross laminated timber and glulam through a sustainability and efficiency lens. We start with a brief summary of the life cycle from forest to wood product, then compare mass timber and conventional construction whole building life cycle assessments, identify challenges in implementing mass timber construction projects, and highlight opportunities for extending the life cycle by designing for disassembly (DfD) and reuse. Both material and process implications of using this novel construction material are discussed. Dr. Oneil’s focus will be on the life cycle from forest to wood product with emphasis on characterizing elements of sustainable procurement decisions.

Breakout Topic:
Life Cycle Assessment of Mass Timber Products and their use in Buildings Compared to Traditional Building Materials
Maureen Puettmann, Director of Operations, CORRIM

-Mass timber construction can have a greater carbon displacement benefit, because it moves wood into building designs that traditionally have been dominated by steel and concrete materials. Cross-laminated timber is at the forefront of the mass timber movement, which is enabling designers, engineers and other stakeholders to build taller wood buildings. Cross-laminated timber panels are made by laminating dimension lumber orthogonally in alternating layers. Among the environmental advantages of CLT are that it is a natural carbon store and that its use generates virtually no waste at a building site, as panels are generally prefabricated before delivery. Panels made from CLT are lightweight yet very strong, with good fire, seismic and thermal performance. Cross-laminated timber and other mass timber products production and use are still in the early learning curve, and requires additional research to track how it responds over time in terms of lower embodied carbon from changes in production, as well as building design.
-We are just at the beginning of assessing the environmental impacts of mass timber components and their environmental performance in buildings. The carbon mitigation potential of mass timber buildings goes well beyond the embodied carbon from cradle to construction gate. Studies are underway to assess environmental performance and regional differences of mass timber buildings, compared to traditional buildings of concrete and steel ranging from 8 to 18 stories. We will not know the true carbon benefit until we assess the different applications for mass timber in high-rise buildings by displacing steel and concrete, the potential for a longer service life, and the opportunities for reuse and recycling. One can expect many innovations in how a mass timber wall or floor will be used, given that use is just at the beginning of a technology-driven learning curve.