The master of engineering in Integrated Wood Design program at the University of Northern British Columbia (UNBC) equips design and construction professionals with knowledge of wood use, building science, and sustainable-design principles. As the program grew, the need for increased laboratory space became apparent. First conceived of in spring 2016, UNBC’s new Wood Innovation Research Lab (WIRL) opened its doors in April 2018 and received Passive House certification in July 2018.
The WIRL is a 10-metre-tall single-storey mixed-use building with a large two-bay lab space, a separate classroom, and office spaces. It is being used for research and testing related to wood construction and Passive House. The lab is equipped with a concrete strong wall and floor, complete with hold-downs for three-dimensional testing of wooden structures. An overhead crane runs the length of one bay for the manoeuvering of large specimens. The shop also includes three universal testing machines, a CNC cutting machine, and a 34-m2 wood-conditioning room that is equipped with ventilation and humidification to create an ideal environment for normalizing wood specimens to a consistent moisture content.
Meeting the Passive House standard was particularly challenging, for three reasons. First, temperatures in Prince George swing from 30°C to –30°C during the year, with 234 heating or cooling days per year. Second, because of the need for a very tall lab space, the building envelope area is rather large compared to the small thermally treated floor area. Third, the building’s program requirements created complex challenges. A large bay door was needed to afford access for semi trucks. The cutting machinery throws off significant dust volumes, which require a large dust extraction system, posing significant airtightness challenges. And the hydraulic pumps for the structural testing equipment generate massive interior heat gains.
The superstructure is composed of mass timber glulam columns and beams on a 6-metre grid. The building envelope was framed using dimensional-lumber trusses that were prefabricated into one-side-open 10-metre-tall wall panels. These were over 500 mm thick to meet the thermal performance requirements; framing them with upright trusses accommodated this thickness in a cost-efficient way.
The shipped panels consisted of OSB on the inside, followed by a smart air- and vapour-barrier membrane for airtightness and vapour diffusion control, and then the truss structure. Once the panels were craned into place, the builder sealed the seams of the airtight layer by reaching through the wall to the membrane. Then the panels were closed from the bottom up with another layer of OSB on the outside and filled with blown-in mineral fibre.
Exterior to this OSB was a layer of building wrap, then strapping to form a rain screen gap, and the mostly painted metal siding. The interior layer of OSB was left exposed as the finishing for the lab portion of the building.
Most of the windows are located on the south-facing wall, and their sizing was optimized to allow for sufficient daylight while limiting overall frame length. Heat losses through the roof were managed by applying an average thickness of approximately 610 mm of sloping EPS insulation.
A layer of 215 mm of EPS was applied continuously under much of the foundation. However, a portion of the 30-metre by 30-metre concrete raft slab foundation is a strong floor: a high-capacity 1-metre-thick section of reinforced concrete that will be used for structural testing. Reducing thermal losses through this section required a special-ordered high-strength EPS.
As for airtightness, careful design and meticulous implementation during construction resulted in an impressive achievement: 0.07 ACH50. “The compactness of the building and the simplicity of the envelope worked in our favour,” says Guido Wimmers, chair and associate professor of UNBC’s Integrated Wood Design Department. “But there were also significant pitfalls.”
An overhead shop door was a lab requirement that presented a logistical challenge, as these doors aren’t typically airtight. The solution was a German-manufactured door that fully seals, thanks to rubber gaskets pressed airtight between each panel and the surface where the door meets the floor, and to an ultrahigh-molecular-weight polyethylene profile and track that reduces friction when the door is being opened or closed.
Wood dust is unavoidable when working with wood, but it can represent a significant health risk, as the particles can be small enough to irritate the respiratory system. Removing dust involves moving large volumes of air, leading to heat losses. To reduce these, a dust-extraction system with a recirculating function was installed. The air is transported out of the building, and the dust is removed through a large cyclone filter. Then the air comes back into the building, passes through very large 1-micron pocket filters, and is eventually distributed back into the laboratory. The system can be operated in bypass mode, in which case the exhaust air is not recirculated. This mode is only used when cedar or hardwoods are processed. As the volume of extracted air is very large, a door must be opened to allow for enough airflow. Consequently the lab users agreed to process these woods only during the summer months.
For continuous ventilation the WIRL relies on an HRV with a heat recovery efficiency of 80%. The building’s small heating requirement of only 9.8 W/m² is met using a 35-kW gas-powered furnace—roughly the same capacity as a furnace serving a code-compliant single-family house. The heat is distributed using in-floor radiant heating with a low-flow temperature of approximately 22°C.
A comparative life cycle assessment was conducted to estimate the impact of the materials’ embodied energy versus operational energy on the overall building emissions over its lifetime. Generally, operational energy impacts far outweigh the embodied energy of the materials used in the building. However, in Passive House buildings that ratio can shift as operational energy is minimized. “We were surprised to find that the ratio of operational to embodied energy over the lifetime of the WIRL would be roughly 60-40,” says Wimmers. These results emphasize the importance of first reducing the operational energy of a building. Once high-performance standards have been achieved, the selection of materials for the superstructure and the building envelope becomes increasingly important.
Passive House Metrics
Cooling and dehumidification demand
Primary Energy Renewable (PER)
After the first 12 months of occupancy, the building’s actual energy use is very close to what the PHPP modelling predicted, according to Wimmers. “Accounting for the differences between the actual weather and the PHPP climate data and the fact that not all the equipment was installed, the error is definitely less than 10%,” he says. “The WIRL is another proof of the high level of accuracy you can achieve with PHPP.”