High Rise Buildings Could Become Permanent Carbon Sinks If We Build Them Using Wood

May 21, 2017 – In the town of Prince George, British Columbia, an 8-storey, 30-meter tall building stands out from its neighbours. Why? Because it is constructed almost entirely of wood. And wooden buildings may represent a future trend as civil engineers and architects recognize the carbon sink benefit derived from using this natural material. A building made of wood is a net carbon sink. A building made of steel and concrete generates significant greenhouse gas emissions (GHGs).

The tower in Prince George isn’t the tallest wooden building on the planet. Bergen, Norway has the Treet, which translated means “The Tree,” standing 14 storeys and 52.8 meters in height. And Vienna, Austria is building the HoHo, which when completed this year will stand 24 storeys and 84 meters in height.

For conservationists, the idea that using wood for large building construction is beneficial to the environment seems bizarre. After all, you are cutting down living trees and harvesting the wood. Wouldn’t that be equivalent to destroying a natural carbon sink? If we are talking about sustainable forest practices, harvesting trees shouldn’t reduce its carbon sink capacity. That, of course, only holds true where forests are properly managed.

The advantage of wood over traditional steel and concrete is more than just environmental. Wood is stronger than steel and concrete compared kilogram to kilogram. And according to research at University of California, buildings made of wood withstand earthquakes far better than those of steel and concrete. Wood is a better insulator keeping building interiors cooler in summer and warmer in winter. And counterintuitively, properly treated wood resists structural damage in a fire better than steel and concrete. Steel melts and concrete cracks, whereas, wood may scorch while continuing to retain structural integrity.

And counterintuitively, properly treated wood resists structural damage in a fire better than steel and concrete. Steel melts and concrete deforms and cracks, whereas, wood may scorch while retaining structural integrity. The construction material used in the Prince George building, Douglas Fir, a commonly found tree in the Pacific Northwest of North America, was char tested and showed that it could endure an hour of fire with penetration limited to 39 millimeters over that amount of time.

The industry knows wood because it has been used in residential homes as a primary material for centuries. But what the industry didn’t realize until it started measuring GHG contributions, the manufacturing and transportation of concrete and steel represent an enormous GHG emission volume. The architects of the HoHo project in Vienna, where 76% of the building will be made of wood, estimate a saving of 2,800 tons of GHGs over concrete and steel. Overall emissions, when compared to concrete, will be 1/8th that of an equivalent building made of concrete and steel. States one engineer, “when you compare a wood building with a concrete building, wood wins every time.”

If more buildings are built using wood, are the forests sustainable? Currently, in the United States, 80% of all houses are of wood construction. The total impact on existing forest stocks is equal to a third of the annual forest growth. Experts believe that use of wood in building construction could easily double without impacting the natural carbon sink capacity of existing forest stocks. And that building with that kind of wood volume would equal putting out of commission 9 utility-sized coal-fired thermal power plants.

The government of Finland in doing its own studies for the European market estimates that increasing wood use by 4% annually for construction in the European Union would reduce carbon emissions by 150 million tons annually, equalling the total annual emissions of The Netherlands.

Two remaining challenges exist:

1. Right now wood as a construction material is largely confined to North America and Europe. To be an effective GHG reducing strategy it must expand to other areas of the globe.
2. The longevity of wood construction needs to be further assessed. If the buildings have a standing life of a few decades then there is the danger that deconstruction will reintroduce the captured carbon into the atmosphere through landfill emissions. The buildings have to endure for centuries. And in the case where a building is deconstructed the wood cannot be left to rot and emit carbon, but must be fully recyclable for use in future construction.

So wood, made from carbon, may become one of the most important tools for humanity in developing a zero carbon economy. Where else could we see would replace steel or concrete? In ships? In other forms of transportation? Why not?