Mass timber: Thinking big about sustainable construction

MIT class designs a prototype building to demonstrate that even huge buildings can be built primarily with wood.

View of the Longhouse Northwest Elevation Image: MIT Mass Timber Design
View of the Longhouse Northwest Elevation Image: MIT Mass Timber Design

Scientists worldwide are searching for the ways to make buildings more efficient and less dependent on emissions-intensive materials. Likewise, MIT scientists have developed a highly energy-efficient design for sustainable construction of a large community building from world’s oldest construction materials.

In particular, scientists used the Longhouse, massive timbers made of conventional lumber. The design is expected to explore new application for this material including safe and sound high-rise buildings.

John Klein, a research scientist in MIT’s architecture department who taught a workshop called Mass Timber Design that came up with the new design, explains that “in North America, we have an abundance of forest resources, and a lot of it is overgrown. There’s an effort to find ways to use forest products sustainably, and the forests are actively undergoing thinning processes to prevent forest fires and beetle infestations.”

“Most of the builders have already started using mass timber for construction purpose. One of the largest mass timber buildings in the U.S. is the new 82,000-square-foot John W. Olver Design Building at the University of Massachusetts at Amherst.”

View of the Longhouse interior during a co-working staging Image: MIT Mass Timber Design
View of the Longhouse interior during a co-working staging
Image: MIT Mass Timber Design

People’s major concern after listening about such type of construction is fire. But, lab-test have suggested that using mass timber can resist fire better than steel. It is fire resistant because, wood exposed to fire naturally produces a layer of char, which is highly insulating and can protect the bulk of the wood for more than two hours.

The newly designed structure includes massive beams made from layers of wood veneers laminated together, a process known as laminated veneer lumber (LVL), made into panels 50 feet long, 10 feet wide, and more than 6 inches thick. These are sliced to size and used to make a progression of large curves, 40 feet tall to the central peak and spanning 50 feet over, made of areas with a triangular cross-segment to include structural strength.

A progression of these curves is assembled to make a vast encased space with no requirement for interior basic backings. The pleated design of the rooftop is designed to suit sun oriented boards and windows for natural lighting and latent sun solar heating.

Demi Fang, an MIT architecture graduate student who was part of the design team said, “The structural depth achieved by building up the triangular section helps us achieve the clear span desired for the communal space, all while lending a visual language on both the interior and the exterior of the structure. Each arch tapers and widens along its length, because not every point along the arch will be subject to the same magnitude of forces, and this varying cross-section depth both expresses structural performance while encouraging materials savings.”

Klein said, “One obstacle to greater use of mass timber for large structures is in current U.S. building codes, which limit the use of structural wood to residential buildings up to five stories, or commercial buildings up to six stories. But recent construction of much taller timber buildings in Europe, Australia, and Canada — including an 18-story timber building in British Columbia — should help to establish such buildings’ safety and lead to the needed code changes.”

Steve Marshall, an assistant director of cooperative forestry with the U.S. Forest Service, who was not involved in this project. Longhouse is a wonderfully creative and beautifully executed example of the design potential for mass timber. The mass timber is poised to become a significant part of how America builds.”

“The sustainability implications for the places we live, work, and play are huge. In addition to the well-known ramifications such as the sequestration of carbon within the buildings, there are also community benefits such as dramatically reduced truck traffic during the construction process.”

The Longhouse design was developed by a cross-disciplinary team in 4.S13 (Mass Timber Design), a design workshop in MIT’s architecture department that explores the future of sustainable buildings. The team included John Fechtel, Paul Short, Demi Fang, Andrew Brose, Hyerin Lee, and Alexandre Beaudouin-Mackay. It was supported by the Department of Architecture, BuroHappold Engineering, and Nova Concepts.

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