Mass timber: Thinking big about sustainable construction

///Mass timber: Thinking big about sustainable construction

Mass timber: Thinking big about sustainable construction

The construction and operation of all kinds of buildings uses vast amounts of energy and natural resources. Researchers around the world have therefore been seeking ways to make buildings more efficient and less dependent on emissions-intensive materials.

Now, a project developed through an MIT class has come up with a highly energy-efficient design for a large community building that uses one of the world’s oldest construction materials. For this structure, called “the Longhouse,” massive timbers made of conventional lumber would be laminated together like a kind of supersized plywood.

The design will be presented this October at the Maine Mass Timber Conference, which is dedicated to exploring new uses of this material, which can be used to build safe, sound high-rise buildings, if building codes permit them.

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.”

People tend to think of wood as a suitable material for structures just a few stories high, but not for larger structures, Klein says. But already some builders are beginning to use mass timber products (a term that basically applies to any wood products much larger than conventional lumber) for bigger structures, including medium-rise buildings of up to 20 stories. Even taller buildings should ultimately be practical with this technology, he says. 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.

One of the first questions people raise when they hear of such construction has to do with fire. Can such tall wooden structures really be safe? In fact, Klein says, tests have demonstrated that mass timber structures can resist fire as well or better than steel. That’s 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. Steel, in contrast, can fail suddenly when heat softens it and causes it to buckle.

Klein explains that this natural fire resistance makes sense when you think about dropping a lit match onto a pile of wood shavings, versus dropping it onto a log. The shavings will burst into flames, but on the log a match will simply sputter out. The greater the bulk of the wood, the better it resists ignition.

Read more at Massachusetts Institute of Technology

2018-08-08T08:20:47+00:00 Tags: |