The move towards mass timber Buildings – Part II

HVAC and plumbing challenges and the state of mass timber in Canada

By Jonathon Harp


Mechanical systems can have a profound effect on the aesthetic appeal of the interior of the structure with its large open spaces, high ceilings and attractive wooden beams.

This is the second in a two-part series about how builders are starting to embrace mass timber construction as a desirable option for residential and commercial buildings. In this second part, we look at the challenges designers and contractors encounter when installing HVAC and plumbing systems in mass timber structures, as well as a review of the state of the mass timber industry in Canada.

The move towards mass timber buildings is underway and gaining momentum each year. Contractors need to stay abreast of this new construction sector and how it will change the way

mechanical systems are designed and installed. For more information, go to the International Association for Mass Timber Construction ( and the Mass Timber Institute (



Experts point to the HVAC and plumbing system design as one of the most important construction processes builders and mechanical trades have to address for mass timber structures. These systems can have a profound effect on the aesthetic appeal of the interior of the structure with its large open spaces, high ceilings and attractive wooden beams.

From the outset, the designer has to determine how the installation of these systems will mesh with the architectural look of the interior of the building. These design decisions will have a significant effect on the way mechanical systems are installed. In essence, the decisions will determine what components of the systems will be visible versus hidden to create the interior look desired by the architect and builder.

If the architectural design for the structure uses the mechanical systems as a part of the interior look, ductwork, piping and other mechanical components can simply be left uncovered and blend into the architecture. If hiding some or all of the system components is determined, a number of options are available to the designer for the trades to use.

Two such options are building “light frame walls or soffits” and “furring out” mass timber walls. The light-frame wall option can be located on one or both sides of the mass timber wall panels to house HVAC and plumbing system components. The “furred out” option involves expanding a portion of the lower half of the mass timber wall (similar to wainscoting) to house mechanical system components.

Where the design calls for retention of as much of the “wood look” as possible, other solutions need to be used to hide the systems for aesthetics and retain good system performance.

One such option used in mass timber buildings is an “underfloor air distribution system” (UFAD). This system manages the balance between efficiency and aesthetics without requiring the extensive ductwork systems used in traditional HVAC systems. The “underfloor” aspect of the system is actually a raised access floor installed above the air distribution system. UFADs can also be used to run piping and other mechanical components.

Logistically, the raised access floor is built after the mass timber construction is complete and in a configuration that will house the complete HVAC system including ducts and diffusers. The result is a system that is completely hidden and maintains the majority of the building’s aesthetic value. Another benefit of the UFAD system is the mass timber construction process for the building is completed before the mechanical system’s work is started, which makes the whole construction process move quickly and more efficiently.

UFAD systems provide a wide range of improved performance aspects compared to traditional systems, including less time for installation, reduced loss of useable space, less energy use through more efficient air circulation and better ventilation.

The bottom line is design and installation of HVAC and plumbing systems in mass timber buildings take careful preparation and participation by contractors in the design process to ensure trade concerns are taken into account as the design unfolds. There are many options to meet the design expectations and contractors need to have their say on what is needed to “get the job done properly.” And don’t forget, local energy and building codes need to be reviewed to ensure the options used meet local and provincial requirements.



As conceptualized, the Canada Earth Tower in Vancouver will be the world’s tallest hybrid mass
timber building.

In 2021, Natural Resources Canada (NRCan) in partnership with the Green Construction through Wood program released The State of Mass Timber in Canada 2021, an inaugural report on mass timber construction.

Seamus O’Regan, minister of Natural Resources at the time the report was released, stated “Canada is a world leader in building with wood, and we’re building bigger and taller buildings. Mass timber buildings are highly resistant to earthquakes, offer natural thermal insulation, are inherently fire-resistant, and can be rapidly installed. They’re also a critical nature-based solution to climate change, and an important part of getting to net-zero.” The report covers the progress of manufacturing and building with mass timber. There is an increasing demand in Canada for sustainable building materials and “sophisticated design and production systems.” The report indicates that mass timber will play a key role “in low carbon construction and developing the bio-economy.”

Canada has completed or has under construction 702 mass timber projects with institutional (283), commercial (173) and residential (58) being the leading sectors. The report contains background on these projects, which represent more than 1.5 million square metres of gross floor space. There are also 21 mass timber manufacturing facilities across Canada.

One of the more prominent Canadian projects is Brock Commons Tallwood House, a student residence at UBC. The Commons is a test project of 18 storeys in height. When it was opened in July 2019, the building was “the tallest mass timber structure in the world” according to Wikipedia. The structure is 53 metres tall with a capacity of 404 students, a floor area of 15,120 square metres and is considered a “hybrid” in that it uses some concrete and steel in the construction.

Two other projects of note that are in the works are the Academic Tallwood Tower (ATT) at the University of Toronto and the Earth Tower to be constructed in downtown Vancouver. The ATT will be a 14-storey hybrid made of mass timber and concrete. The Earth Tower will be 37 storeys in height and could be the tallest mass timber structure in the world when completed.