Faster cleaner quicker greener: why tall wood is the coming thing
Willow Aliento | 6 April 2017
The University of British Columbia in Vancouver is showcasing faster, cleaner, quieter and greener multistorey construction with what is believed to be the world’s tallest mass timber reaching full completion next month.
The Brock Commons Tallwood House project will provide student accommodation for over 400 UBC students, and the 18-storey, 53 metre high structure was completed in less than 10 weeks.
Russell Acton, principal of Acton Ostry Architects in Canada, says this is four months faster than a conventional concrete and steel project.
The building is a hybrid approach. Concrete was used for the ground floor, the lift cores and the emergency exit cores.
Steel straps have been incorporated as part of the seismic protection strategy. The straps transfer seismic forces to the lift cores, Acton says.
The rest of the structure comprises cross-laminated timber panels and glulam columns.
This resulted in avoiding and sequestering carbon emissions equivalent to taking 511 cars off the road for a year.
It also meant one third of the truck movements compared to a conventional project, a much quieter construction site and reduced waste.
The project was sponsored by the government of the Province of British Columbia, which held a national design competition calling for a project that could be built out of mass wood.
It also pledged to help fund the “innovation gap” in terms of the difference in cost compared to a conventional project, Acton says.
This amounted to around eight per cent higher costs due to the “first time” nature of the development.
A preliminary cost comparison was done showing the cost per square foot was around $236, ($2540 a square metre) compared to $207-$212 per square foot ($2228-$2255 a sq m) for standard mid-range product in the Vancouver housing market.
Acton says the university has a strong emphasis on green building, including the use of glulam and CLT construction.
It also has a forestry school, and the province itself recently adopted a “Wood First” policy to promote the use of timber in construction. The policy means timbers must be considered the material of choice where they will be fit for purpose.
However, special permission was still required for the project to proceed, as the current iteration of the province’s construction code limits timber to six storeys as a deemed to satisfy solution.
“We had to get a site specific regulation,” Acton says.
This meant needing to “prove out” the fire engineering and structural engineering solution to two separate panels, each comprising 20 experts.
“It was a bit onerous.”
He says he hopes, however, that have demonstrated the viability of the solution it will “make it easier for others” to follow suit in future.
There are between five and six years between changes to the BC building code, he says. The next one is scheduled for 2020. Any tall wood project before that date will also require special permission.
Acton says the hope is that the 2020 iteration will include both an encapsulated solution pathway and an exposed timber pathway for tall wood.
Brock Commons has encapsulated the timber, with plasterboard in the interiors and a facade comprising prefabricated panels.
The project was able to source its CLT and glulam from within the province, just 300 miles from Vancouver, he says.
The manufacturer was shipping the prefabricated panels, which were designed in a variety of sizes, and the glulam columns down through the build period.
All of the elements were CNC routed for every required hole, shaft, void and other penetrations.
“It was designed through vigorous design process,” Acton says.
The project used a consultant he says provided “BIM on steroids” services for the project.
This entailed virtual construction modelling which was not just a model of the design, but also the construction methodology and every component down to screws and bolts.
This then allowed the trades and consultants to critique the design and methodology and optimise the construction process for efficiency and safety.
The exactness and detail also helped make life easier and quicker for the trades, as everything aligned to within 2mm tolerances and no on-site variations were required.
Acton says the virtual construction modelling process should “be the way of the future”.
He says the same about mass timber-dominated hybrid construction.
It’s an application that suits the “background buildings” that make up the majority of any city.
“What I’m interested in is more of an application where it’s not about interesting stuff. I am interested in extraordinary ordinary stuff
“Designing a showcase building is kind of fun, the constraints are not at the forefront, but for low and middle income families and individuals, I am more interested in speaking to how can this technology be used for ordinary buildings.”
As an application, it is affordable, economical, looks great and is sustainable. In terms of thermal and acoustic performance, it also performs as well or better than any other building system, Acton says.
The thermal requirements for UBC buildings, for example, are quite high he says. The university also requires all its new buildings to achieve LEED Gold Standard for energy efficiency.
To get Brock Commons to that standard was “just detailing” in the design of the facade, Acton says. That included reducing thermal bridging and increasing insulation.
The building will also be connected to UBC’s own district energy system.
The project has stirred global interest, he says, with the practice receiving calls from LA, Japan and elsewhere from parties keen to have his firm design them a tall timber building.
“I always ask them, how are you going to get your approval [to construct]?”
“There are a lot of challenges and a lot of education needs to happen with the [building approval] authorities.”
Projects seeking to follow the tall wood path will “need to go through proper protocol”.
“With the authority we built with, they are very conservative,” Acton says.
But by choosing to present a conservative solution involving a very simple, straightforward design with thorough engineering for fire and structural safety, no issues were raised with the solution by the approval bodies and panels of experts.
“We took a belt and suspenders approach to the project.”
Acton says they got their building permit in “record time” of just three months.
“It’s just very straightforward engineering,” Acton says.
“If we can put a man on the moon, we can build tall timber buildings,” he says.
The fire, seismic and structural aspects are all “very well understood”.
The fact the construction process is also “quick, clean and quiet” is a clear advantage, he says.
Brock Commons’ site, for example, is in a “difficult neighbourhood” in terms of undertaking multi-storey construction.
“In the future, quick, clean and quiet will be a critical selling point for development,” Acton says.
As more projects are developed, and “things get competitive” the costs will also go down and approvals will streamline.
The mass timber supply for the project, for example, was open for tenders from anywhere in the world. It had bids even from Europe.
But while CLT is cheaper to manufacture in Germany and Austria, the cost of shipping it to BC made it more expensive than the local product.
“If Austria can get the costs of manufacture down, it is a no brainer that in future costs in Canada will drop considerably,” Acton says.
By comparison, concrete and steel are already mature industries that have “reached cost minimum.”
Acton says the project’s structural engineer says the hybrid solution as implemented for Brock Commons would be fit for purpose for as high as 30 storeys.
“Past 30 storeys other aspects would be needed of concrete and steel to assist the building, but you could still have a 90 per cent wood building.”
For UBC, there is another advantage of the project that would make sense to any developer.
The interior will be complete by May 30th, Acton says. This means students can start moving in from July.
That gives the university a few months of extra income from rents compared to the traditional September opening.
Acton says the practice is looking forward to undertaking more wood projects, and as a matter of course incorporates wood “wherever we can.”
In terms of more tall wood developments, he says “time will tell”.
Real momentum could be a few years off until the building code changes.