Figuring out the best means of constructing cladding and associated wall systems (including attachment methods and sequence of installation) can be daunting for an architect.
“We try and steer the drawings in a direction that allows those types of issues to be dealt with and detailed very efficiently from a labour perspective,” says Michal Chlumecky, vice-president of operations, Contract Glaziers Inc. (CGI), a Canadian company in the business of making and installing building envelope systems.
CGI and other building envelope specialists are gaining more work early in the design stage of some projects in what is called a design-assist (DA) role. DA contracts especially make sense on projects with high-performance envelope materials applied in complex geometries, he points out. How these materials are designed and installed can have “dramatic cost implications” for the owner.
John Spadaro, director of engineering, Flynn Canada Ltd., agrees, pointing out that that DA contracts are gaining popularity in the world of fast-track projects, and on contracts where owners are “looking to carefully manage risk.”
On big projects, building envelope companies can save architects a lot of time puzzling over building envelope details, he adds.
The concept of design-assist has been around for many years but only recently has it moved from the arena of pro bono service to that of a formal contract for technical support, says Spadaro. Contractual arrangements can range from a design consultancy where the contractor is not retained to install the system, to an implied agreement where the DA contractor is awarded the supply and installation as long as the project’s costs stay on target.
Typically, a company like CGI and Flynn might advise an architect on systems for wind loading, maintenance and cleaning, building tolerances and movements, building code, and water/air infiltration. “We can review the architect’s design with respect to strength, weather-tightness, and durability, and if necessary suggest modifications to improve the performance and reduce cost,” says Chlumecky.
Those modifications might include alternative fixing methods, assembly sequencing revisions, or even different cladding materials. The contractor might also check interface provisions to ensure the façade design is coordinated with the construction of the rest of the building.
CGI also works with mechanical engineering and contracting teams to establish a building envelope performance that yields efficiencies and economies of scale. Sometimes this results in more curtainwall elements to increase energy performance.
While that might hike the costs of the curtainwall, it might allow for less expensive mechanical equipment, bringing the overall building costs down, Chlumecky says.
While there are plenty of sound reasons for design-assist contracts, some owners steer clear of them because they want to keep accountability in the architect’s hands. That isn’t always a smart move. Chlumecky points to a DA contract where CGI made “a lot of value engineering suggestions” on a hospital’s curtainwall design that yielded a 10 to 15 percent savings on the costs of the building envelope without compromising the architect’s design intent. Prior to CGI’s input, the architect had unknowingly designed details that were adding costs to the project.
DA contracts are gaining respect in such building sectors as health care – particularly for contracts in fast-track mode. About 40 percent of all of CGI’s health care contracts today are design -ssist, says Chlumecky.
DA is also moving into other building sectors. Recently, CGI was awarded a high-performance dual skin curtainwall based on a design assist business model for expansion at the Calgary International Airport. Flynn Canada, meanwhile, recently completed a pre-glazed high performance custom unitized curtainwall at Epcor Tower, a 29-storey office tower in downtown Edmonton. The triple glazed unit configuration consists of three pieces of 6 mm glass separated by two 12.7 mm argon-filled cavities and Low E coatings on two surfaces.
Made by Flynn, the curtainwall goes a step further to improve energy performance through the use of a polymide thermal break to separate the interior aluminum from the exterior, says Spadaro.
Traditional curtainwalls that have thermal breaks such as PVC systems are normally fastened to the interior aluminum with screws. Tests show that the screw penetrations can increase the U-value (the rate at which heat flows through glazing) by 10-15 percent.
“The approach we took eliminated the bridging of those screw penetrations,” explains Spadaro, noting that the break consists of a series of struts secured and crimped together to the inside of the exterior. The technology has been around Canada for about a decade but it hasn’t been used often. That could change because of the increased demand for energy efficiency designs, says Spadaro.
For design-assist to be successful, all parties involved must understand the architect’s performance objectives and budget, and the architect’s design intent must be maintained, says Chlumecky.
In-experienced parties or parties taking an adversarial approach can cause breakdowns, says Spadaro, adding another possible negative is that design-assist draws a contractor’s resources much earlier into a project than tendered contracts do.
DA is most successful when it is a collaborative effort, he sums up.
This article was written by Don Procter and originally appeared in the June/July 2011 print edition of The Trowel.
