Prince George, B.C. – When an explosion rocked the University of Northern British Columbia’s Wood Innovation Research Laboratory (WIRL) one year ago, the first concerns were for safety and wellbeing, but the event became a rare opportunity to examine the resiliency of the mass timber structure in the aftermath.

WIRL is a centre for world-class research on wood mechanics and timber structures. Built in downtown Prince George in 2018 to the stringent international Passive House (Passivhaus) standard for energy efficiency, the University lab set a Canadian record for air tightness. 

Early on the morning of August 22, 2023, WIRL faced a test that none of its designers could have imagined. A large natural gas explosion razed the adjacent building, damaged numerous other structures and injured three people.

The pressure wave from the blast shook the building much like an earthquake. Debris punctured WIRL’s exterior cladding, allowing fire to enter the building. As it burned through the wall, the interior sprinkler system engaged and extinguished the flames, but the building was flooded. 

In the space of a couple of hours, the lab experienced the equivalents of an earthquake, fire and flood.

“The main – and first and foremost concern – was about the safety of our students and lab technicians and fortunately no one was in the lab at the moment of the explosion, so that was the first relief,” says UNBC School of Engineering Professor Dr. Thomas Tannert. “And then, like over the next hours, my main concern was how would this impact our research.”

From its inception, WIRL has been both a lab where UNBC researchers conduct leading-edge experiments as well as a model structure. It served the latter purpose as the reconstruction process illustrated why the building was so resilient and what factors limited the impacts.

“It’s pretty rare that you get to see a building that you designed go through something as extreme as an explosion right next door,” says Aspect Structural Engineers CEO and Principal Adam Gerber. “Honestly, first impressions (are) that the building performed really, really well.”

Several core components of the building are credited with its ability to survive the blast. The flexible mass timber structure brought two advantages: it absorbed the blast’s force, bent, and then returned to normal; and with it being independent of the wall panels, those panels were easily replaced while the mass timber structure still stood. Additionally, the use of floor joists in those exterior wood panels provided durability and strength, and the gaps in the joists were filled with insulation made from ground-up rock that acted as a barrier to the fire.

“In the end, I think everyone has been convinced that the building has performed beyond anyone’s expectations in general,” says UNBC School of Engineering Associate Professor Dr. Asif Iqbal. “And that has been a very reassuring fact for us.”

Passive House is a voluntary energy-based standard in design and construction. UNBC has chosen to invest in Passive House buildings because the energy efficiency furthers the University’s goals towards sustainability while delivering occupant comfort.

“And what we’ve learned is that the value that was added for thermal performance sustainability also provides value for its resiliency,” says Stantec architect Derreck Travis. “So, as we move into this climate change and increase in traumatic fire events, there (are) some lessons to be learned about how this type of construction adds value not only in economics and sustainability, but also resiliency.”

The events in downtown Prince George last August model the value of mass timber design to the global community. WIRL’s resiliency will allow researchers to continue their work to inform the next generation on safe, modern, energy-efficient mass timber construction.