Worried about wood? Brock Commons Tallwood House is probably one of the safest buildings anywhere.
We're not called TreeHugger for nothing, and love the new wave of tall wood buildings. Right now, the tallest of the tall wood buildings is Brock Commons Tallwood House, at the University of British Columbia. It's a student residence and has just been occupied for the first time. We have shown it before, when it was topped off last year.
When built from sustainably harvested wood, these buildings store carbon for the life of the building. Wood is a renewable resource; according to Naturally Wood, a British Columbia wood promotion organization, US and Canadian forests grow the amount of wood used in this building in six minutes.
One of the biggest knocks against wood construction (at least according to the concrete and masonry industries) is the fact that wood burns. They like to run big ads every time a construction site catches fire, complaining that wood isn't as safe as concrete. But the new tall wood buildings are made from Cross-Laminated Timber (CLT) that doesn't burn very well at all. When solid wood is exposed to fire the exterior of it chars, which actually provides an insulating layer; this has been known for hundreds of years, which is why heavy timber buildings were designed with larger members than were just needed for structural reasons. CLT works the same way.
But that's not good enough when you are building 18 storeys tall and filling it with students, especially when the local British Columbia building codes limit the height of wood buildings to six storeys. So in the case of Brock Commons, a special regulation was developed, and a serious belt-and-suspenders approach to fire safety was used. Acton Ostry Architects worked with a team of consultants to rewrite the book on fire safety.
The building is described as a hybrid, because the stair and elevator cores are poured concrete, providing a completely noncombustible means of exit. Then every bit of wood (except in a lounge on the top floor) is encased in layers of fire-rated drywall to provide a minimum two hour fire rating between floors and between units. The suites are not very large, so that creates a lot of fire separated compartments on every floor. Things that might go boom, like the mechanical and electrical services, are all kept within the concrete ground floor.
Then there is a sprinkler system with backup pumps, standpipes and a water curtain on the big ground floor exterior glazed panels. Because the building is in an earthquake zone, there is a 5,283 US gallon tank of water that can run the sprinklers for 30 minutes if the municipal water supply is cut off. They even use recessed pop-out sprinkler heads that are flush with the ceiling so that those pesky students won't knock them off.
There is another benefit of building in wood in an earthquake zone: it is a lot lighter. "The lower mass results in less inertia and therefore lower resistance to overturning during a seismic event. The concrete foundation and ground floor provide a counterweight to resist overturning forces." This TreeHugger has been dubious about about really tall wood buildings (see Too much of a wood thing...), but concrete is not the best way to build in earthquake zones, where light weight and flexible joints make buildings safer.
If we are serious about reducing our carbon footprint, we have to stop using concrete wherever possible. Brock Commons/ Tallwood Tower demonstrates how this can be done in taller buildings. When the ready-mixers and blockheads complain about wood construction, remember that the point of fire protection isn't to save the building, but to provide the means and the time for the people inside to get out. And with all the attention Brock Commons got, it's probably one of the safest buildings in the world.
Read more at Naturally Wood, which has case studies on every aspect of this building.