Sustainable Northwest (SNW) and Hacienda Community Development Group (HCDC), both based in Oregon, have proposed a plan to demonstrate pathways for building affordable housing with regionally sourced mass timber. In response to the region’s housing shortage, the partners’ proposal demonstrates the use of mass timber products while supporting efforts to educate stakeholders on wood product companies and forest restoration. The project outlines a plan to explore financing options, build one or more prototypes, and perform a structural material life cycle analysis.
Project contact is Pierre Blanchet at Université Laval
The work of Lessard et al. (2017) demonstrated that the building envelope was an important system in the building in terms of environmental impact, but only took into account the external components of the building envelope. This project will perform a life cycle analysis of the main building envelopes for a typical building under commercial construction. By relying on our design partners, the main systems and associated materials will be analyzed in a cradle-to-grave approach. It is desirable to identify hot spots and to indicate avenues for product development in order to reduce the envelope's environmental footprint. Among the scenarios to be considered: light framework, CLT, curtain walls and all their possible variants, but also commonly used non-biobased systems. The comparison between the systems studied will be based on an equivalent energy efficiency performance.
The Nature Conservancy is leading a multi-institution collaboration to quantify the potential for innovative mass timber materials to support improved forest management, revitalize forest economies and mitigate greenhouse gas emissions. Life cycle assessments (LCAs) of engineered timber products such as glued laminated timber (glulam) and cross-laminated timber (CLT) in construction have highlighted their environmental advantages over conventional materials such as concrete and steel. However, there is little understanding of how developing new markets for such materials could support the wood product sector and the management of US forests. This applied research will assess in detail the potential impacts of large-scale growth in mass timber demand on wood product markets, timber harvest, forest management and climate change mitigation in key wood-producing regions across the USA and globally, as well as opportunities to leverage these markets to support US forest management and rural economies. The findings will be used to produce peer-reviewed publications and design a suite of targeted stakeholder engagement materials and programs, providing an objective, credible fact base to inform the design of policies and programs to maximize environmental and economic benefits of mass timber use for the forest sector.
The primary outcome of this work is to provide integrated analysis of the environmental, financial, and social benefits and costs of using CLT in tall wood buildings. Secondary outcomes will be (1) information, including a design team checkoff that can be used to inform the building community as they make decisions on specific, new building projects, and (2) an informational foundation for these stakeholders and others to begin to evaluate the complex tradeoffs between, and optimization of, environmental, financial, and social benefits and costs.
This short report summarizes a life cycle assessment (LCA) study comparing a cross-laminated timber mid-rise building to the same building in concrete1. For more detail, refer to the original report which was the product of a rigorous, comparative LCA research project that complied with the international LCA standard ISO 14040:2006. In that study an apartment building in Quebec City, Canada was analyzed using two different building systems in order to understand the environmental footprint of each relative to the other. A LCA model was developed for a real, 4060 m2, 4-storey, cross-laminated timber (CLT) apartment building. The same building was then designed using reinforced concrete slabs and columns with light gauge steel stud walls. That design was intended as a building system that CLT would likely be compared with in the midrise construction market where CLT is likely to compete.
We conducted a systematic literature search and meta-analysis of studies with side-by-side life cycle analysis comparisons of mid-rise buildings using mass timber and conventional, concrete and steel, building materials. Based on 18 comparisons across four continents, we found that substituting conventional building materials for mass timber reduces construction phase emissions by 69%, an average reduction of 216 kgCO2e/m2 of floor area. Studies included in our analysis were unanimous in showing emissions reductions when building with mass timber compared to conventional materials. Scaling-up low-carbon construction, assuming mass timber is substituted for conventional building materials in half of expected new urban construction, could provide as much as 9% of global emissions reduction needed to meet 2030 targets for keeping global warming below 1.5 °C. Realizing the climate mitigation potential of mass timber building could be accelerated by policy and private investment. Policy actions such as changing building codes, including mass timber in carbon offset crediting programs and setting building-sector-specific emissions reduction goals will remove barriers to and incentivize the adoption of mass timber. Private capital, as debt or equity investment, is poised to play a crucial role in financing mass timber building.