Climate change is the impetus for numerous design and construction improvements, but the shift to better buildings isn’t always smooth sailing, especially when best practices aren’t followed.
A good example is with the design and construction of facades, which are “on the front lines of all the wear and tear of a building,” said Jeff Ker, senior technical adviser with Engineered Assemblies, a large facade company based in Toronto.
The facade industry has moved to lighter weight materials and lower mass designs to reduce embodied energy (initial and recurring), cut costs and increase durability “for an incredibly long time,” Ker told a webinar audience recently at the CSC Building Expo.
The challenge is for designers and builders to make sure their projects meet these objectives.
It can be a big ask.
Ker, who gave a seminar on the most common mistakes in the facade industry, said facade materials and the substructure holding them in place need to be better engineered to meet the performance standards for which they are capable.
He said inadequate ventilation makes his list of common mistakes in the industry, both at the design and then the installation stage.
Proper ventilation keeps the envelope dry, he said, noting that a 25-millimetre plenum between facade materials and insulation meets the objective.
The plenum also serves to exhaust heat from buildings during hot spells and helps to keep facade materials at a balanced temperature, adding longevity to the envelope.
Ker said another common mistake his company sees through investigations into facade system problems and failures in Canada is that substructures don’t move because they lack proper fixed and floating fastener points.
In many parts of Canada — the Greater Toronto Area is a prime example — temperatures rise and fall significantly in winter causing freeze/thaw conditions that require facades to have an expansion/contraction design, he told the audience.
Some types of large panels, typically up to four metres long, will contract and expand one millimetre per metre of panel.
On a recent project Ker saw cracking panels because floating fasteners were “not centred” in the holes drilled for them. While phenolic core panels are not apt to crack in these scenarios, they could buckle, he added.
He said rivets often make better floating fasteners than threaded fasteners because rivets maintain the same tension. The tension of threaded fasteners varies depending on the installer.
Proper floating and fixed fastening designs are not a cost factor but they will help ensure long-term facade performance.
Ker said the company’s new version of its design guide covers these points and other information design and construction industries should know.
Another common weak point in today’s lightweight facades is an inability to withstand a lot of deflection. One of the keys to getting the design right without adding much cost is a substructure system that uses omega channels that are stronger on a through plane than a Z-bar, he said.
Also important is that the installer use proper materials that meet the deflection limit requirements to “ensure the survival of the building envelope.”
In some cases, poor facade performance is due to “common negligence” on the part of the installer.
As an example, Ker pointed to a project where a subcontractor took an installation shortcut by leaving the bottom ends of some panels on a building unfastened because the omission could not be seen from grade level.
Ker questioned the sub’s decision for the move. There was no notable cost savings and the time to install each panel end would have only been about one minute.
“This is the kind of carelessness we’re seeing in some respects.”
He added another common mistake is inadequate shop drawings (installation crew instructions). They are not inexpensive but “great shop drawings will save time, save money,” Ker said.
“It means you’re not going to be cut and pasting common details from a manufacturer’s website.”
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