oN5 Building

Insulative CLT assemblies and damage-resistant seismic design

Named for its location near the intersection of Ontario Street and East Fifth Avenue in Vancouver, this innovative four-storey project demonstrates what is possible with mass timber construction including new approaches to insulative cross-laminated timber (CLT) assemblies and damage-resistant seismic design.

Located in the Mt. Pleasant neighbourhood of Vancouver—a community filled with architecture and design firms—oN5 serves as a demonstration project showcasing high-performance mass timber construction and design.  

High-performance energy-saving design

The structure was designed to Passive House principles, one of the most rigorous voluntary energy-based standards in the design and construction industry today. Its efficient design, along with wood’s natural insulating benefits, helps reduce the need for active heating and cooling systems by optimizing the building envelope. Most of the heat is provided by a heat recovery ventilator. And by adding extra insulation and taking other design measures, the building requires very little in the way of energy for mechanical systems.  

Fire-resistant CLT construction

While current building codes typically require exterior walls of a zero-lot-line urban infill structure to be made of non-combustible material, the team arrived on an alternative solution that uses fire-resistant CLT panels as exterior walls. Wood’s ability to char—forming an insulating layer protecting interior wood from damage—means the CLT panels provide natural, predictable fire resistance. 

Breathable and insulative prefabricated CLT panels

The load-bearing CLT shear wall panels arrived at the jobsite prefabricated for quick, easy installation. 200-millimetre-thick mineral wood insulation and rainscreen cladding was pre-applied to the outside of the CLT wall panels. This approach followed Passive House design principles that wall assemblies be breathable to the outside. 

Seamless connections using an innovative CLT adhesive system

CLT floor panels were connected without the need for beams or steel connectors. The project used an innovative adhesive system that connects the ends of the CLT floor panels forming a rigid diaphragm. The pioneering adhesive system uses a resin, which was injected into the small gap between the CLT floor panels. The glue feeds itself into the cells of the wood, creating a solid, seamless connection. The technology allows mass timber to be used for flat slab construction, making it comparable to concrete in terms of interior clear heights, flexible layout and efficient construction. 

A seismic design that nearly eliminates damage during an earthquake 

The building uses an innovative, resilient slip friction joint system, developed in New Zealand, that will dissipate seismic energy and restore the structure to centre after an earthquake. While the unique system works the same in terms of energy dissipation regardless of structure type, it works particularly well with mass timber since wood is one-sixth the weight of concrete, reducing forces during a seismic event. 

We feel that as engineers, we have a responsibility to put our money where our mouth is. We want to provide an example to society while doing something good for the environment by using mass timber. The City of Vancouver and British Columbia are leaders in wood excellence, and we’re proud to be part of it.

Robert Malczyk, structural engineer and owner

More on the project