Not only is timber a renewable natural resource, building with wood can amplify the carbon sequestration ability of our forests.
As trees grow, they absorb carbon from the atmosphere and – powered by photosynthesis – convert it into the organic molecules of living plant matter. Carbon is stored within the roots, trunk, branches, bark, and leaves of the living tree. Under natural forest conditions, the stored carbon is slowly released back into the atmosphere after the tree dies and decomposes.
However, if the wood from the tree is sustainably harvested, this carbon storage can outlast the life span of the tree. The timber – with its stored carbon – can endure for centuries, incorporated into our buildings. A seedling growing in the place of the harvested tree will begin the process of carbon sequestration anew.
Mass timber has the potential to magnify the carbon sequestration potential of sustainably harvested wood, by expanding the use of structural timber into building types formerly constructed of conventional steel and concrete. Featuring an innovative use of engineered timber, the John W. Olver Design Building is the largest cross-laminated timber (CLT) academic building in the United States. It demonstrates the sustainability, economy, and beauty of mass timber as a building material and renewable resource.
Leers Weinzapfel worked with WoodWorks and the Athena Institute to use the Olver Building as a test case for the potential of mass timber to reduce carbon emissions over the life cycle of the building. Harnessing the carbon-sequestration potential of sustainably-sourced wood, the timber structure effectively removes 2,681 metric tons of carbon from the atmosphere. A comprehensive life cycle analysis by the Athena Institute evaluated the complete energy used by the building – production, transportation, construction, maintenance, and demolition – and found mass timber construction reduced carbon emissions by 13%, CFCs by 10% and non-renewable energy use by 15%, compared to conventional (steel/concrete) construction.
Energy is inevitably required to construct buildings, as well as to operate and maintain them. However, the choices we make — to reduce energy use, to obtain our energy from renewable sources, and to sequester carbon instead of releasing it — can ensure that energy approaches carbon-neutrality.
