Significance of Time Value When Comparing Alternatives for Building Decarbonization

Decarbonizing buildings globally requires accurately quantifying the global warming impact of construction materials. However, standard carbon accounting methods and metrics undermine the potential of fast-growing biogenic materials because they ignore the timing of carbon uptake. The consequence is that analyses can indicate a building material is carbon-neutral when it is not climate-neutral. Here, we investigated the time-dependent effect of using fast-growing fibers in durable construction materials. The study estimated the material stock and flow and associated cradle-to-gate embodied emissions for four residential framing systems in the US: concrete masonry units, light-frame dimensional timber, and two framing systems that incorporate fast-growing fibers (bamboo and Eucalyptus). The carbon flows for these four framing systems were then scaled across four adoption scenarios, ranging from business-as-usual (no adoption of fast-growing fibers) to highly optimistic (full adoption of fast-growing materials in new construction within 10 years). Dynamic Life Cycle Assessment modeling was used to project radiative forcing and global temperature change potential. The results show that adoption of fast-growing biogenic construction materials can significantly reduce the climate impact of new US residential buildings within this century under reasonable adoption scenarios. However, net climate-cooling from residential framing will require highly aggressive, immediate adoption of fast-growing biogenic materials.