August 31, 2023

Embracing the mass timber revolution

Clem

Lewis

As we grapple with the challenges of climate change, the construction and design industries have turned their attention to an age-old material with a modern twist: wood.

Once widely used in construction, wood became subordinate to concrete and steel in the 19th and 20th centuries. This meant less research and fewer use cases for wood construction.

In the last few years, however, wood — mainly in the form of engineered mass timber products — has experienced a resurgence, as testing and research has established wood construction as not only as safe as concrete and steel, but also sustainably superior.

In our decade of working with mass timber at Skanska, we’ve seen how it has sped up construction schedules and reduced cost. Using mass timber also significantly reduces a project’s carbon footprint, while satisfying clients’ desire for biophilic design through mass timber’s rustic, natural aesthetic.

In short, mass timber is redefining the way we build for a sustainable future, bolstering sustainability, construction efficiency and aesthetics.

Sustainability

It’s regenerative

Sustainability is a key differentiator between mass timber and other building materials like concrete and steel. Countless elements make mass timber one of the most sustainable building materials today, and chief among them is its regenerative nature.

Image courtesy of Mithun [enlarge]

Mass timber is used throughout the Center for Deaf and Hard of Hearing Youth in Vancouver, Wash., with the aim of improving comfort, mood, health and productivity.

Sourced from a correctly managed forest, timber is not only carbon friendly, but also an inexhaustible resource. Removing gravel, limestone, iron, or sand from the ground is inherently extractive; those resources do not replenish naturally. However, with mass timber, sunlight, water, chlorophyl, and good soil eventually convert into structural building materials — an outstanding regenerative cycle.

A more complete carbon picture

Carbon footprint is critical when determining sustainable building plans. Skanska teams evaluate the carbon impact from sourcing mass timber overseas versus locally, as well as the intricacies of forestry practices, shipping, delivery and installation. Timber’s comprehensive carbon-tracking supply chain, encompassing forestry, harvesting, and milling, allows a more thorough identification of carbon impact levels that can be discussed with clients. That’s not always the case with other building materials, which often rely on calculations that overlook significant contributors to the production process, as well as downstream effects of sourcing.

Deconstruction is possible

Timber also offers more modularity, as you can deconstruct a building and reuse large parts of the timber in nearly full structural capacity, whereas most other structural building materials get downcycled.

Construction Efficiency

Time in the factory, not on site

Mass timber offers a substantial reduction in construction time across project duration — from prefab to finish — vs. steel or concrete. The key lies in the ability to shift significant portions of the process to a controlled factory environment. With field cutting eliminated, further work simply requires mechanical, electrical, and plumbing subcontractors on site to place the ducting, electrical cables, and other items, vastly reducing construction time.

With school construction, schedules are strict because back-to-school dates are set in stone and new buildings need to open on time. Using mass timber as a major component —like in the new Fairview Middle School Skanska is building in Bremerton. — not only adds a modern design element, but also helps reduce the construction timeline when there isn’t any wiggle room.

Image courtesy of Skanska USA Building [enlarge]

Early concept drawing of a nine-story, 150,000-square foot mass timber tower in Bellevue that Skanska is developing and building.

The taller the building

As building heights rise, time savings grow dramatically. Skanska recently spearheaded a comprehensive study to evaluate potential building materials in our own development of a nine-story, 150,000 square-foot superstructure in Bellevue. The findings revealed that employing the new 2024 International Building Codes for exposing the timber proved that a mass timber building would be cost competitive and slash construction time by three months in comparison to conventional concrete construction.

Timesaving is attributed mainly to mass timber’s modularity and close coordination with the structural core and exterior envelope, which are pivotal in setting the project timeline. Mass timber also provides superstructure cost savings due to the prefabrication of timber components; however, the real savings comes from pre-coordination with other trades such as MEPF, stairs, elevators and exterior wall systems.

Because Skanska can self-perform not only mass timber, but also steel and concrete construction, we have been able to deliver highly complex, high-quality projects in shorter timeframes and with leaner budgets. Industry standard suggests a 20% reduction, and Skanska has seen projects that exceed that.

More cost-savings under new codes

Further reducing time and cost with mass timber — or rather increasing time and cost for concrete construction — are the forthcoming changes to building codes in seismic areas in the Northwest. Skanska recently completed conceptual estimates with both current codes and schematic estimates with new codes, finding that, in a concrete superstructure, there was a 10 percent increase in superstructure cost due to the added weight and seismic impacts. The pending 2024 IBC code adoption further optimizes mass timber by removing some of the requirements to encapsulate the timber, reducing cost and carbon impact, and retaining a natural connectivity to the wood.

Aesthetics

Mass timber also delivers a captivating aesthetic that resonates deeply with the concept of biophilia, our innate connection to nature. Left unfinished, mass timber adds a rustic, natural and streamlined look, while eliminating costs such as wall finishes. The beautiful nature of wood allows unique architectural designs to stand out. Mass timber not only elevates a space’s visual appeal, but also enriches lives through a direct impact on occupants’ mood, health, and even productivity.

University of Oregon’s Kevin Den Wymelenberg recently published a study surrounding the “visual effects of wood on thermal perception of interior environments.” Through this, the team successfully proved that wood materials in structures improved thermal comfort. In other words, people said the room’s temperature felt more comfortable with wood walls than with white painted walls.

The expansion of the campus for the Center for Deaf and Hard of Hearing Youth in Vancouver, Wash., which is being delivered using progressive design build in collaboration with Mithun, is a great example of how mass timber is being used for this purpose. Research is demonstrating that improved comfort in the classroom has a direct correlation to improved learning outcomes and reduced stress, and is beneficial to both physical and mental health.

Enticing workers back

Visual appeal is a big consideration in encouraging a return from home offices, as well. Traditional workplaces with acoustic ceilings and windowless conference rooms just don’t have the draw of the appealing aesthetics of mass timber. Imagine bringing nature indoors — offices built with spacious layouts, large windows flooding the space with natural light, and a focus on biophilic design. This aims to create a charming workplace, enticing teams back into the office after several years of remote work.

Overall, mass timber stands as an undeniable force across construction, reflecting a harmonious blend of sustainability, efficiency, and aesthetic appeal. Embracing this approach heralds a new era in building for a resilient future.

Steve Clem is senior vice president- project planning services for Skanska USA Building in Portland. Dean Lewis is director of mass timber & prefabrication for Skanska USA Building in Seattle.

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