Comparing the embodied carbon and energy of a mass timber structure system to typical steel and concrete alternatives for parking garages

As operational energy use is minimized through high-performance design, construction and systems, the embodied carbon and energy from building materials and construction will play larger roles in the environmental impact of buildings. Consequently, the structural system should be a primary target for reducing the embodied carbon and energy of a building. Parking garages offer an ideal case study for comparing the embodied carbon and energy of different structural systems. As parking garages have little operational energy use and have few materials or systems, the embodied carbon and energy of the structure comprises a majority of the environmental impacts during its life-cycle. This study uses manual material take-offs from construction documents of four parking garages with one-way spans; one pre-cast concrete, one post-tensioned concrete, one cellular steel and one mass timber. The resulting comparison shows that there is little difference in the embodied carbon and energy of structural systems used for parking garages under best material practices. Mass timber, while more viable in a worst-practices scenario, loses its advantages when cement replacement and high recycled content steel are utilized.