1 De Haro
1 De Haro is a 170,000-sf, four-story office building in San Francisco’s Design District and is comprised of three levels of mass timber construction (cross laminated timber [CLT] and glulam framing]) over one level of concrete. While its upper three levels are for office usage, the ground-level concrete podium is for light industrial work. The milestone project holds multiple titles, including the CLT building in the City of San Francisco and the first multi-story mass timber building in California. The structure was topped out in February 2020 and the building was ready for occupancy in Summer 2021.
Mass Timber and Concrete Focus
With site soils, the project team needed to reduce the weight of the structure, so explored the option of mass timber. Mass timber also provided a sustainable component to the project as it equates to roughly 2,000-metric tons of stored carbon. While the concrete component of 1 De Haro was a factor in weight, the team was able to approach its usage with sustainability standards, performing a retroactive Life-Cycle Analysis.
DCI performed a retroactive Life-Cycle Analysis (LCA) on 1 De Haro. During procurement, DCI received two different sets of concrete mix submittals for the cast-in-place concrete portion of the building: one mid-grade set with 15-30% cement replacement and one high-grade set with 70% cement replacement in the foundations, plus 20-50% for all other applications. All high-grade mixes also contained the carbon injection admixture, CarbonCure. When compared to the NRMCA Pacific Southwest Baseline, the cradle-to-gate GWP of the entire structure was reduced by 5% with the mid-grade concrete mixes and 20% with the high-grade concrete mixes.
DCI found that the foundation elements provided the biggest opportunity for embodied carbon reduction. The global warming potential associated with the high-grade foundation mixtures was nearly half of the mid-grade and NRMCA Pacific Southwest Baseline mixtures.