How Can Construction Innovations Make Housing More Affordable

Mass timber products are a building material manufactured in factories from pieces of wood that, when connected with glue, nails, or other materials, are strengthened. Two types of common mass timber products are glue-laminated timber (glulam) and cross-laminated timber (CLT).

Glulam is formed from wooden boards pressed together in a parallel direction, connected with glue. CLT is created from wooden boards pressed together in a perpendicular pattern. Mass timber is often mentioned in conjunction with “tall-wood” buildings.

These are multistorey buildings—some up to 25 stories—that are built using a preponderance of timber products, including mass timber. To reach their tallest possible size, a mix of steel and concrete may also be incorporated. Mass timber has been used for over 20 years in Europe and, in the Canadian province of British Columbia, all provincial buildings are required to be mass timber.

Mass timber is lightweight yet provides equal or greater weight-bearing capacity than steel or cement, reducing the amount of building material needed for structural support and expediting construction. ThinkWood, a lumber materials education association, estimates that a four-story wood building could cost 30%-40% less than a traditional building using only steel and concrete for load bearing. 3

• Mass timber lends itself well to the prefabrication of large building segments that can be precisely manufactured in factories, shipped to building sites, and erected quickly using less labour.
• Some products, especially glulam, are considered inherently or aesthetically attractive. Depending on the design, this can eliminate the need for more expensive or labour-intensive finishings, such as drywall or paint. Sustainability and carbon removal:
• Mass timber and other lumber products are more environmentally sustainable than steel or concrete because these wood products store sequestered carbon dioxide. In contrast, steel or concrete are estimated to provide 13% of global carbon emissions according to the OECD.
• Mass timber ideally uses trees under a 10-inch diameter so that brush cleared to reduce wildfires, which normally could only be used as biofuel, can be used as input for mass timber. Enhancing market demand for so-called waste biomass will help reduce fuel loads in forest—a critical need as the wildfire seasons become longer and more frequent.
• Harvesting and fabrication of mass timber and prefabrication of building segments can provide new sources of rural economic development. An example of the benefits of using wood construction is a six-and-a-half story, mid-rise apartment building in Sacramento, CA where the developers relied on the cost savings generated to ensure the project was financially feasible.

A seven-story, mixed-use affordable housing development in Boise, ID also relied on mixed wood and concrete. In this case, the design and use of lumber and mass timber allowed the builder to incorporate off-site prefabrication, resulting in shorter, more efficient construction schedule. While mass timber has many benefits, it has not been immune to the increases in lumber prices seen over the past two years.

Supply chain issues remain a concern too, as there is limited manufacturing capacity for these new products. As a result, research is being conducted on ways to create mass timber products using weight-bearing plywood. This would be an important development, by helping reduce costs when experiencing fluctuations in lumber prices.

Oregon State University and the University of Oregon are partnering on one such pilot project, which involves a building constructed of mass timber plywood.

I N N O V AT I O N 2:

S T R U C T U R A L INSULATED PANELS

Structural insulated panels (SIPs) consist of two sides of strand board (a form of high-performance particle board) on either side of an insulated foam core. While research is ongoing to assess SIPs’ wind resistance, load-bearing capacity, lifecycle costs, and energy efficiency, they show great promise. These panels can be precision fabricated to fit together like a puzzle on a building site, collectively forming an energy efficient building. SIPs can streamline the production process and therefore lower costs, compared to traditional stick-building. Currently, as lumber prices have skyrocketed, there is some research that SIPs are also proving more cost effective.