“The best time to plant a tree was 20 years ago. Now is the second-best time.”

Sometimes attributed to an ancient Asian proverb and other times cited as a common saying from modern times, this quote appropriately references a grown material that takes years or decades to reach maturity. Wood is newly becoming appreciated in old ways. 

We are exploring aspects of materiality including embodied carbon, circularity and so-called “externalities” such as equity, and health—which is inspiring even in this “second best” time. (See glossary here).

Embodied carbon is becoming a well-known concept. A term that may still require clarity is “biogenic carbon,” which is somewhat debated in the building industry around the frameworks for measurement and the proper value to assign to stored carbon.

Trees take in CO2 and express oxygen. This CO2 is considered to be drawn down or sequestered over the life of that tree, and stored as biogenic carbon for the full time that the wood is protected from decomposition or combustion, for example in buildings. 

Biogenic carbon is a fast cycle when compared to fossil fuel cycles, so we can feed the cycle with new cultivation of growth and sequestration as we access wood for use in buildings. 

We can benefit, carbon-wise, from many grown materials: using agri-waste in mycelium-based foam production, straw used in bale construction, bamboo and other grasses in finishes or insulation, and by wood waste compressed and glued into OSB or other substrate materials.  

Mass timber—all things new

You may be familiar with mass timber structures through old warehouse and factory buildings of the upper Northeast, where heavy, exposed wood columns and beams make the spaces feel soaring and grounded simultaneously. The corners of these columns are chamfered, meaning cut off at an angle, to reduce the impact of fire on the massive wood. 

What is old is new again, and this type of construction is becoming prominent as the fire-resistive capacity is tested and confirmed. 

Mass timber construction (per the 2021 International Building Code (IBC) is allowed up to 18 stories, with specific requirements per building type for non-combustive protections. In wood frame buildings, the 2024 IBC allows exposure up to 100 percent of mass timber ceilings and integral beams, while the 2021 IBC allowed only up to 20 percent for these elements. Twenty-eight states have adopted some level, usually with local amendments of the 2021 or 2024 IBC provision on mass timber. 

Benefits of mass timber

Modern mass timber, such as that used for structural framing, and composite laminated timber (CLT)—most often used for walls and flooring—is often a composite of layers of wood that is adhered, pinned or nailed together. This massing of the wood still achieves significant fire resistance, and the structural benefits ironically outweigh steel and concrete as there is more strength in compression per pound. The comparative lightness of mass timber means foundations can be less massive, and/or excavations can be reduced. CLT can allow for great increases in spans, thereby reducing material use for the structural framework. 

In many cases, this wood can be left exposed, further reducing the materiality of the building while reconnecting people to the beauty of natural materials.  

Mass timber columns, beams, and panelized floors and walls are well suited to pre-manufactured processes for making the connections and openings. This off-site machining makes for a significant reduction of waste materials through the tight controls that can be used at an off-site facility despite weather issues. This also results in clean, fast and relatively quiet site-work as well. There is also great potential for cataloguing mass timber elements for eventual deconstruction as reuse. Norway is taking the lead in this regard.

The SUNY College of Environmental Science and Forestry has focused on mass timber for several years, with research, presentations and competitions led by a team of professors and contributors. Focus points include the understanding of the life cycle, including forestry practices and planning; material properties; systems, including manufacturing; and market acceptance and outreach. The opportunities for carbon reduction, local forestry practices, human connections to nature through biophilia, and life cycle systemic accountability are significant. 

Although mass timber cannot and should not be used for every building, and we need to learn much more about forestry management as part of this complex life-cycle and system, we should all be inspired to discover what is possible for our work ahead. In a word to the wise, plant a tree today!

Jodi Smits-Anderson is a subject matter guide (SMG) and collaborative leader with deep experience in embodied carbon, energy codes, the AIA Framework for Design Excellence and in identifying the synergies between the false silos we have created in our industry. Acknowledging that full-spectrum sustainability is a set of core principles that improves all work is a mental leap Smits-Anderson strives to cultivate with every team and in all work. Her passion for this work is, frankly, that it is more fun to work with great people and more joyful to learn and evolve that work.