5 Things Developers Should Know About Mass Timber

Editor's Note: This article was originally published in 2022. It has been updated throughout with the latest information.

The United Nations' latest International Panel on Climate Change (IPCC) report contains an urgent call to action for the building industry. The report stresses the urgency of near-term integrated climate action, noting that the "window of opportunity to secure a livable and sustainable future for all" is rapidly closing. As designers and architects, we must make buildings less carbon intensive in order to mitigate the worst effects and prevent a runaway, irreversible climate change scenario. With an inherently low carbon profile, mass timber can make a big impact towards tackling climate action and achieving those goals.

The effects of climate change like drought, extreme weather events, and sea level rise, are already having far-reaching impacts on the health and well-being of all living things. According to the IPCC, even if global warming is limited to 1.5°C, up to 14% of species assessed will face a high risk of extinction and more than 3 billion people across the globe live in contexts that are highly vulnerable to climate change.

The building industry accounts for approximately 39% of all global greenhouse gas emissions. At the COP28 U.N. climate summit in 2023, Gensler Global Co-Chair Diane Hoskins reaffirmed our commitment to carbon neutrality in our work and operations by 2030 and initiatives like the Gensler Product Sustainability Standards that will help us reach that goal. However, as the IPCC has noted, an additional 2.5 billion people are projected to move to urban areas by 2050. This global migration poses a tremendous opportunity to adapt the urban built environment to reduce greenhouse gas emissions.

The role of embodied carbon

Global greenhouse gas emissions can be categorized in two major categories: embodied and operational emissions. Embodied emissions are the ‘baked in’ carbon dioxide (and equivalent gas) emissions associated with material sourcing, manufacturing, and construction, and end of life. Operational emissions are associated with the building performance after completion. Both types of emissions are generally measured in carbon use intensity (kgCO2e/SF) and are combined to understand the overall carbon profile of a project. Although operational emissions are typically 60-70% of the overall emissions over the lifespan of a project, embodied emissions will contribute approximately 75% of overall emissions associated with new projects over the next eight years. As the IPCC report outlines, the level of greenhouse gas emission reductions we make this decade will largely determine whether global temperature rise can be limited to the crucial 1.5°C. Embodied emission reductions strategies are equally, if not more, important than operational emission reduction measures.

What are the materials that contribute to embodied carbon emissions and what strategies do we have available to us to reduce these emissions? Structural materials such as steel and concrete account for most greenhouse gas emissions due to energy intensive manufacturing processes. Concrete alone accounts for approximately 10-15% of all embodied carbon emissions associated with the built environment. To change the trajectory of the building industry, we must find alternatives to steel and concrete.

The promise and potential of mass timber

It is in the context of the climate crisis that the mass timber movement has taken root and spread. Mass timber is an umbrella term for a wide variety of engineered wood products that can structurally replace steel and concrete and lower carbon emissions. There are two main reasons mass timber structural systems have relatively low embodied carbon profiles: avoided emissions from not using steel and concrete, and carbon sequestration through photosynthesis over the lifecycle of the harvested trees. According to the IPCC report, strategic conversion prevention of forests and other ecosystems can reduce 4 gigatons of carbon dioxide emissions a year, second only to solar energy as a potential contributor to net emission reduction by 2030. So how does harvesting trees protect forest ecosystems? The purchase of sustainably sourced mass timber products assigns monetary value to forests, conserving the existing forest stock by discouraging land use conversion.

Here are five things developers need to know to include mass timber in their next project:

Although not a silver bullet, mass timber is one of many strategies industry players can leverage to reduce global greenhouse gas emissions. Timber is a renewable resource that is underutilized as a structural material. North American forests produce enough timber to build a 100,000 square foot mass timber building every seven minutes. Tree harvesting occurs on less than 2% of forest land annually, compared to close to 3% of forest land that is annually disturbed by insects, disease, and fire. Mass timber projects can contribute to holistic sustainability stories that are attractive to tenants, benefit the environment, and are good for the bottom line. What are we waiting for?