Bloom, EthanChidambaranath, PallavlFretz, MarkKwok, AlisonMahic, AlenMartin, KatherineNorthcutt, DaleRowell, JoshuaStenson, JasonVan Den Wymelenberg, KevinOnell, ElainePuettmann, Maureen2024-10-172024-10-172023https://hdl.handle.net/1794/3012065 pagesThe carbon story for buildings exemplifies the complexity and interconnection of embodied and operational carbon contributing to global greenhouse gas (GHG) emissions causing climate change. A myriad of considerations are in play, from natural resource management, extraction, processing, transportation, construction, operation and ultimately end of life, for every material and every building. Buildings currently represent about 37% of annual global CO2 emissions.1 About 10 GtCO2 annually come from building operations, which is at an all-time high, and about 3.6 GtCO2 from producing major materials used in building construction.1 As the world economy grows and living standards rise, the global consumption of raw materials is expected to nearly double by 2060.1 Decarbonizing the building sector will require coordinated action from numerous and diverse stakeholders in areas such as science, policy, and finance. Architects, engineers, and construction (AEC) professionals can take greater responsibility through building material selection, but this important decision-making process requires having the right data at hand when it’s needed. We believe the quickest means to reducing global warming potential through building material selection in the near term is to: 1) use and reuse materials efficiently, including existing structures; 2) use low embodied-carbon material options in place of materials that are derived from carbon intensive production; 3) employ bio-based materials, such as timber, that are renewable and remove carbon from the atmosphere during their growth, then design for durability and longevity, disassembly, and end-of-life reuse to ensure that the stored carbon remains out of the atmosphere for as long as possible; 4) create opportunities to use mill and production waste in products with long lifespans. At present, timber is typically less carbon intensive than steel or concrete if sourced from forests with sustainable forest management practices. On a longer time horizon, we believe: 1) significant reductions in all industry emissions and continued improvements in sequestration are imperative for all building materials including wood, concrete and steel; 2) transitioning a significant percentage of our buildings and cities to timber structures could significantly reduce carbon emissions in time, but only if sustainable forest management practices are used in concert with strong forward-thinking governance and broad-reach planning efforts; 3) sustainable forestry practices, along with the life cycle assessment methodologies and design tools used to quantify their impacts, are still in a period of development and refinement, and should be expected to be a moving target in the foreseeable future with advancement in our collective understanding and through greater adoption of these systems and practices. This guide, Carbon Narratives for Design Planning, was developed to acknowledge areas of influence when considering selection of mass timber as a primary building material. It is a complicated narrative, but one that designers and their clients are embracing based on multiple positive attributes of mass timber. At the same time, there is consensus that more transparency and uniformity in the embodied carbon story of wood products from forest to building site will lead to more informed decisions and improved environmental outcomes when specifying materials during design planning. This project offers a synthesis of available information for primary materials of structural building systems, with particular focus given to mass timber. We highlight ways in which mass timber can reduce whole building embodied carbon yet recognize that the narratives become complicated when comparing carbon content in mass timber structural systems against concrete or steel. The narrative becomes further nuanced when forest management practices, biogenic carbon and unknown material end-of-life pathways become part of the equation. The guide is structured in five parts, describing: 1) carbon in the built environment; 2) carbon, climate and forests; 3) carbon and mass timber; 4) carbon and concrete and 5) carbon and steel. Additional resources included in the appendices are survey results from 180 AEC practitioners from across North America, many with international project experience, that were used to structure a series of five workshops that took place between April and September 2021: 1) Wood Certifications: What is the difference and is it worth the extra cost? 2) Beyond the EPD: What aren’t we considering? 3) Comparing Carbon Narratives: How do concrete, steel and mass timber actually perform? 4) LCA Assumptions: Counting carbon neutrality versus climate neutrality? 5) Design for Building End of Life: Assumptions versus Actualities. Workshops drew on expertise and perspectives from individuals in forest ownership and production at small and large scales, manufacturers, non-profits, government and academia. Due to the Covid-19 pandemic, these workshops were held entirely virtual, which allowed participation of national and international experts. Links to workshop recordings are hosted on the Institute for Health in the Built Environment (IHBE) and NetZed Laboratory websites. The immediate goal of this work is to create a common narrative for use by AEC professionals in their current and future work involving specification of building materials and associated carbon impact from those choices. Longer range goals of this work are based on the belief that these carbon narratives are key to advancing research, innovation, and cross-disciplinary urgency surrounding broad efforts to decarbonize the building sector and the materials used in the built environment.Articleen-USCreative Commons BY-NC-ND 4.0-UScarbon storyresource managementcarbon narrativesbuilt environmentOther