April 27, 2007

Planning Techniques

Checklists identify potential envelope design improvements

DAN O’REILLY

correspondent

Building code changes, evolving materials and technologies, and the challenges posed by an over-stretched construction industry are just some of the items required on a building envelope checklist.

“How do we make a better building?” Kevin Day, project manager with Halsall Associates Ltd. asked participants at a recent Building Envelope Solutions workshop.

Achieving that objective isn’t easy or straightforward, especially with the implementation of the new ‘objective-based’ national and provincial building codes, said Day, a past president of the Ontario Building Envelope Council.

Those changes don’t mean design and construction should be done cheaper, although codes and industry standards simply promote minimal performance, he said.

There is the opportunity to improve the performance and service life of a building during the design/decision making process and incremental costs can always be justified, said Day.

An integral part of the design process is analyzing a building’s life cycle costs rather than just considering the capital costs.

"You don't want them to value engineer everything out of your design."

Kevin Day

Halsall Associates Ltd.

While not easy to obtain, the Canada Green Building Council’s LEED Canada green building rating system does include a durability credit, he pointed out.

Value engineering, however, opposes the concept of durable design and often owners and developers only look at capital costs, said Day, urging his audience to resist that trend whenever possible.

“You don’t want them to value engineer everything out of your design.”

If that happens, however, there are subtle improvements that can still be made to the building envelope to reduce life cycle costs.

Some examples include detailed air barriers behind the cavities, using larger screwheads for the sheathing, and installing protective membrane roof assemblies if the owner isn’t interested in a green roof.

“Look for potential improvements that will allow for the greening of the building in the future.”

With benefits such as reduced heat island affects, storm water retention and air cleaning, “the future of the flat roof is green.” But they do have limitations and restrictions, said Day.

Plant growth such as prairie grass may contravene fire ratings, roof drains require ballast guards to prevent soil washing away, and the extra weight of the roof garden at maturity has to be calculated into the structural design.

Touching on other items on the building envelope checklist, Day said designers need to carefully examine the track record and warranties of the various materials and systems they’re considering and the compatibility of adjoining materials such as membranes, metal and concrete.

Building envelope specialists should be included into the design team for high profile or complex projects and/or multiple claddings, he said.

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