What are Canada’s next green leaps?

Wood allows for sustainable expansion in the use of local materials. Specifying wood from certified Canadian sources can also mean support services provided by regional professional firms, thereby increasing local employment and economic activities. Further, RHC Design/Build estimated wood’s affordability improvement (i.e. in terms of labour and material costs) to be 12 to 15 per cent for two recent Ontario projects when compared to steel, assuming all considerations for increased structural enhancements as well as sprinkler systems and fire separations.

It is important thermal and moisture performance principles be understood and applied in the design and construction of mid-rise buildings to prevent health and safety problems. For this project, a condominium construction guide, similar to the high-rise one published by Ontario’s Ministry of Municipal Affairs and Housing (MAH)—a resource that is referenced in NBC—would help with knowledge transfer.

Thermal performance is better with wood construction as there is reduced thermal bridging when compared to steel or concrete buildings. In terms of energy performance, wood buildings have both lower embodied energy and lower operating energy over a 60-year lifecycle, according to the Canadian Wood Council (CWC).

Modelling of wall and roof assemblies in residential buildings that have elevated indoor relative humidity (RH) conditions is critical. In taller buildings, the stack effect is more significant which raises the risks of moisture building up within the roof assembly. Based on recent American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) research conducted in Chicago (a cold climate similar to much of Canada), it was determined moisture would build up on a cathedral roof’s oriented strandboard (OSB) sheathing with a tight air barrier and white roof. A dark roof covering provides additional drying capacity due to heat conduction, thereby reducing moisture levels in the roof assembly and mitigating risk of mould growth.

Constructing taller wood buildings onsite (i.e. without use of pre-fabricated components) will extend exposure time of the structural wood components to moisture and particularly its effects during construction. Therefore, a temporary roof canopy is required to minimize moisture risks from rain. Moisture-mitigation design is also necessary due to the risk of mould growth and rainwater penetration at the numerous windows, doors, balconies, and penetrations typical in current multi-family buildings. Rainscreen wall assemblies must be specified and detailed as a minimum. Building science professionals experienced with multi-family projects are recommended for the design of components and building envelope assemblies.

As mentioned, construction reviews are necessary to check details are being followed; this is especially the case for through-wall flashings and weather protection membranes, as they cannot easily be rectified after the building envelope is finished. Envelope commissioning is also extremely important for wood buildings to achieve proper moisture control at the design, construction, and operational stages. Based on 15 recently completed LEED wood-frame building envelopes commissioned by this author, it was found the installation of through-wall flashings and membranes was a challenge despite proper details being provided. Since mid-rise buildings need the envelope to be compartmentalized at floor levels and window/door openings, experienced trades and third-party review are recommended. A better practice would be to construct the compartments in the factory where they would be protected from the elements, and to use durable pressure-treated woods at the sills.

There are other items, including structural design and fire safety, are being addressed by the industry for mid-rise wood buildings. The use of cross-laminated timber (CLT)—which is similar in some respects to heavy timber—for fire performance is one emerging material. (For more on CLT technology, see the March 2011 Construction Canada article, “The Advent of Cross-laminated Timber,” by David Moses, PhD, P.Eng., PE, LEED AP, and Sylvain Gagnon, Ing. Visit www.constructioncanada.net).

Businesses, neighbourhoods, and communities
Greenbuild’s Canadian contingent is also going to examine the built environment from a larger perspective than simply just individual buildings. In the session titled, “The Green Revolution of the Central Business District (CBD) of Toronto,” Douglas Birkenshaw (B+H Architects), John Lowden (Mitchell Partnership), and Lisa Bate (CaGBC) will discuss how the coming of LEED Gold office buildings has put pressure on the existing building stock to retrofit and upgrade to improve performance.

Similarly, the impact of wider development is covered in two other sessions. “CivicAction Transforms Organizations” is presented by Cara Clairman (Ontario Power Generation [OPG]), John Tory (CivicAction Alliance and radio personality), Linda Mania (Royal Bank of Canada), and Cameron Fowler (BMO Financial Group). “Know Before You Build: Predicting Carbon Profiles of Large-scale, Mixed-use Developments,” will be led by Seth Schultz (Clinton Climate Initiative), Dan Stone (Waterfront Toronto), Eric Miller (University of Toronto), and Albert Wei (Arup).

The CivicAction Alliance of thousands of volunteers has launched a “Green Procurement Initiative,” a “Commercial Building Energy Initiative,” and a “Greening Canada Fund.” The development of its non-proprietary carbon modelling tool will allow decision-makers to better understand integrated large-scale infrastructure systems.

A session dealing with community revitalization is “Evergreen Brick Works: Heritage Industrial Brownfield and LEED Platinum (candidate) Converted into Environmental Community Centre,” presented by Robert Plitt (Evergreen), Joe Lobko (Du Toit Allsopp Hillier), Michael Leckman (Diamond and Schmitt Architects), and Douglas Webber (Halsall Associates). This project serves as a platform to explore and address global issues such as the green economy, urban ecology, transportation, water, energy, waste, agriculture, building design, and land-use planning.

The seventh session is “A Roadmap for Climate Action: Strategies, Tools, and Results,” and is co-presented by representatives of three schools—the University of British Columbia (Nancy Knight), the University of Calgary (Joanne Perdue), and American University (Chris O’Brien). Each institution has already adopted a comprehensive climate action plan and has already realized significant emission reductions.

Conclusion
This article touches on topics that are some of the next steps in innovative green construction that are already being implemented across Canada. These steps are among the strategies and technologies to be discussed at Greenbuild, which should be considered to achieve these leaps in all projects, regardless of size and scope. (For more information on various seminars and the show itself, visit www.greenbuildexpo.org).

Bob Marshall, P. Eng., BDS, LEED AP, is the Canada Green Building Council’s (CaGBC’s) appointed chair for the Best of Canada Bucket Team subcommittee for Greenbuild 2011. He is the country’s appointed expert for the International Organization for Standardization (ISO) Joint Working Group JWG 4 of TC 163-205 on Energy Performance of Buildings using Holistic Approach. Marshall is a member of the CaGBC’s Education Committee. He is a senior building envelope and sustainability consultant at Halcrow Yolles. Marshall can be contacted via e-mail at bob.marshall@halcrowyolles.com.