People are continuously pushing the limits of wood construction. Now, even very tall buildings, once only the domain of concrete and steel, are getting designed using wood as structural components. Proponents claim the payoff can help trim humanity’s greenhouse gas emissions, lower material costs, reduce transportation costs, and speed up on site assembly.
Wood Construction Challenge
Metsä Wood, a Finnish quality wood products producer, along with Michael Green, architect, designed the iconic Empire State Building using wood as the main material. Green is a spokesperson for using wood in modern construction.
“Wood is the only carbon-neutral material that we can build with that’s grown by the power of the sun.” – Michael Green
The redesigned Empire State Building looks just like the original. The height is the same, the floor to floor heights are the same, and the column spacing is the same. Columns go as high as six stories with structural connections along the way that make them continuous for 86 stories. On the short axis of the building, box beams with pretensioned cables inside, tie the structure together. LVL slabs run on the long axis, tying the beams together while becoming their top chords.
The wood materials used in the design are Metsä Wood’s Kerto panels, which are glued together wood veneers made up to eight feet wide and 82 feet long. They are stronger than timber of similar dimensions. The raw wood material is sourced from sustainable growing operations and is certified.
Tall Wood Buildings Historically
Using wood for tall buildings isn’t new. Japanese pagodas more than a thousand years old were built to 19 stories with wood, according to Green. Seven and 10 story heavy timber buildings are now centenarians, and around the world people are designing and constructing buildings made from wood that are 10, 12, 17 and 30 stories high. However, consumers, building code officials, developers and those in the AEC industry have misperceptions about tall wood buildings. These misgivings are roadblocks to greater adoption.
According to Green, speaking at TED, the main components of cities are steel and concrete. Making and using those two materials creates about 8% of mankind’s greenhouse gas emissions. With almost half of the world’s people living in urban environments, and three quarters projected to do so by 2040, Green says buildings are going to stay big. That, he contends, is reason enough to consider a place for wood when constructing them.
The embodied energy of tall buildings made from reinforced concrete and steel is a major consideration in sustainability. And, as a building grows in height its embodied energy grows disproportionately, according to research reported in “Sustainable structural design of tall buildings based on embodied energy.” The paper points out that the type of floor is the most critical component in determining embodied energy use, but lighter floors don’t necessarily mean lower energy use.
The typical lightweight products used in floors, basically plastics, actually increase the embodied energy. No comparison was done for wood floors, as would be possible using laminated products, but there is anecdotal evidence that wood might serve to both reduce weight while also reducing embodied energy.
The need for housing in the world is great. Green claims 40% of the world’s population, representing about a billion people, are going to need shelter over the next 20 years.
This is Construction Informer’s 1,000th post.