Building envelope (enclosure) commissioning may be new to the United States, but it has been around in Canada in one form or another for the better part of two decades. And while some builders see it primarily as a means of dramatically improving energy efficiency, that has never been its prime objective. Envelope commissioning is mainly done to ensure a building’s longevity and durability.
But durability isn’t sexy these days, energy efficiency is, says Mark Lawton, senior building science specialist out of Morrison Hershfield Limited’s office in Vancouver, a city that is on probably on the leading edge of the technology.
In an ideal world, a building envelope consultant is retained in the early stages of a building’s design and sticks around to inspect installation, Lawton explains. The main goal is quite simply to achieve environmental separation. The work involves everything to do with the air tightness of a building and includes pressure resistance—the ability of the air barrier to stop wind loads.
Lawton says Canada’s uniformly cold climate is partly why envelope commissioning developed in the late 1980s, driven largely by Public Works Canada’s efforts to control humidity levels in its buildings. Moisture-related problems were cropping up as a result of buildings that had been heavily insulated during the 1970s energy crisis.
Vancouver’s wakeup call came with the leaky condo crisis in the late 1980s and early 1990s. As a result, the city of Vancouver implemented its own building code (Vancouver Building Bylaw), which requires building envelope professionals to review design and inspect construction of multi-residential frame structures. Air leakage, water penetration resistance, vapor diffusion control and condensation resistance are among their responsibilities, he points out. Builders in the city of Vancouver must have third party warranty coverage on building envelopes.
The city of Toronto doesn’t have a building code so there are no mandatory requirements for enclosure professionals. However, independent building envelope consultants are sometimes retained at the design stage for some types of projects. But it more often starts when a project is nearing completion, says Kevin Day of Halsall Associates Limited.
"It requires some level of review to check that what was designed, and what the owners think they paid for, is in fact performing,” Day says.
The work might include in-situ testing of walls/windows/roofing, thermographic scanning and installing a monitoring system in key areas of the envelope where performance is critical. It might also involve quarterly site visits to measure localized temperatures of the building assembly and identify condensation if thermal bridges are an issue.
A case in point was the dual-barrier roof system that Halsall designed for the Credit Valley Hospital. By monitoring the thermal efficiency of the membrane the consultant demonstrated that keeping the insulation dry in a protected membrane roof was more thermally efficient than a conventional protected membrane system, Day explains.
He says in Toronto commissioning is not widespread, and he doesn’t expect to see rapid growth in the near future unless it becomes a popular LEED® point for new building construction. The Canada Green Building Council has indicated it may add a LEED point for envelope commissioning.
Enclosure commissioning may primarily be a Canadian thing, but Morrison Hershfield and other Canadian consultants have set up shop south of the border. MH has offices in Seattle and Portland, Ore.
Lawton cites an example where Morrison Hershfield was retained for its building envelope expertise by a Canadian architect designing a condo project in Arizona. An insurer required information on what was being done to avoid mold growth. As a result of MH’s work on the envelope, the insurance savings to the owner covered the consultant’s fee, Lawton was told.
"I don’t know if that is true,” Lawton says, "but what has become important when building condominiums in the United States is taking steps (such as enclosure commissioning) to limit liability.”
Don Procter is a free-lance writer in Ontario, Canada.