Oregon and southwest Washington are poised as a manufacturing hub for the emerging Cross Laminated Timber (CLT) market in the United States. The region is bountiful with luscious forestland, a large percentage of which is designated as working forests. Thirty million acres of forest span across Oregon alone. As a value add product that has environmental and social co-benefits, CLT is economically competitive as a structural framing product for multi-story, even high-rise building construction: a market previously dominated by concrete and steel.
The research and outreach activities performed as part of this 2015-2017 study have played a vital role in continuing the advancement of the CLT market in Oregon & SW Washington. Eager regional stakeholders see CLT and other mass timber panel products as forest products capable of providing economic benefit to communities within our region that had grown around forest product industries.
Mass timber building materials such as cross-laminated timber (CLT) have captured attention in mid- to high-rise building designs because of their potential environmental benefits. The recently updated multistory building code also enables greater utilization of these wood building materials. The cost-effectiveness of mass timber buildings is also undergoing substantial analysis. Given the relatively new presence of CLT in United States, high front-end construction costs are expected. This study presents the life-cycle cost (LCC) for a 12-story, 8,360-m2 mass timber building to be built in Portland, Oregon. The goal was to assess its total life-cycle cost (TLCC) relative to a functionally equivalent reinforced-concrete building design using our in-house-developed LCC tool. Based on commercial construction cost data from the RSMeans database, a mass timber building design is estimated to have 26 percent higher front-end costs than its concrete alternative. Front-end construction costs dominated the TLCC for both buildings. However, a decrease of 2.4 percent TLCC relative to concrete building was observed because of the estimated longer lifespan and higher end-of-life salvage value for the mass timber building. The end-of-life savings from demolition cost or salvage values in mass timber building could offset some initial construction costs. There are minimal historical construction cost data and lack of operational cost data for mass timber buildings; therefore, more studies and data are needed to make the generalization of these results. However, a solid methodology for mass timber building LCC was developed and applied to demonstrate several cost scenarios for mass timber building benefits or disadvantages.
MIT Joint Program on the Science and Policy of Global Change
Summary
There has been rapid growth in the use of engineered wood products in the construction sector in recent decades. We evaluate the economy-wide impacts of replacing carbon-intensive construction inputs, such as steel and cement, with lumber products in the US under an emissions constraint. We find that the ability to substitute lumber-based building materials increases production from the lumber and forestry sectors and decreases production from carbon-intensive sectors such as cement. Under a carbon cap-and-trade policy, the ability to substitute lumber products lowers the carbon price and the GDP cost of meeting the carbon cap, with more overall emissions abatement in the construction industry.
Recently, cross-laminated timber (CLT) has attracted attention as a civil engineering material in Japan. In particular, the use of CLT floor slabs for bridge repair is expected to have regional economic impacts throughout their life cycle, but their economic impacts have not been evaluated. In this study, the life cycle regional economic impacts of using non-waterproofed CLT, waterproofed CLT, and reinforced concrete (RC) floor slabs for bridge repair in Akita Prefecture, Japan, were compared. Using past-to-present input–output tables, we quantitatively evaluated the economic impacts over the life cycle of floor slabs by estimating the future input–output tables for construction, maintenance, and disposal. The results showed that the construction and maintenance costs (final demand increase) of CLT floor slabs are higher than those of RC slabs, but the regional economic impact is larger. In addition, the non-waterproofed CLT must be renewed every time it is maintained. Therefore, the demand for CLT production in the prefecture will increase, and the economic impact will be larger than that of the other two floor slabs. This demand for CLT production will not only redound to the benefit of the forestry and wood industry but also the revitalization of regional economies.
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.
