Cold comfort

Choosing the right winter enclosure to keep workers safe and warm through Alberta's coldest months

If you've visited downtown Calgary during the past couple of years, you've almost certainly noticed The Bow. You've also probably noticed a large white sheet wrapped around the building, billowing in the wind.

That simple covering is actually a unique weather enclosure system designed specially for the project by Norseman Inc. It's not a single sheet but a series of interlocking heavy-duty tarps, all attached to a cable system. As work was completed on one floor, the tarps simply slid up or down to shelter the next.

The enclosure blocks out the harsh winds, ensuring that work can continue come rain or snow. But in addition to keeping the weather out, it also keeps the construction materials in.

"They not only wanted it enclosed for safety, but they didn't want a bunch of debris going out the sides," says Percy Gendall, Norseman's vice-president of sales.

Gendall is a big proponent of the safety value of enclosures. "It stops any type of debris falling away from the building," he says. "There have been some situations in downtown Calgary where they have had accidents with debris falling out of a high-rise.

"If these [enclosures] are fixed properly, they'll stop the debris from coming out and it'll also protect anything from coming into the building too."

However, not every construction project is as massive and challenging as The Bow. For many contractors, a lightweight, disposable enclosure system may be all that's needed. So how do you choose a cold-weather enclosure system that works for you?

Disposable systems can include anything from lighter polyethylene tarps to specially designed roll stock that can be wrapped around the scaffolding and then thrown out when the job is done. These systems are often more affordable, but they have their limitations.

"If you do use what they refer to as the lightweight tarps, they really should not be used at elevation," explains Ian Haig, marketing manager, Enscaf Corp. Such enclosures typically cannot withstand the stronger winds found higher up.

That's why most supply companies also offer more durable reusable enclosure systems. These tarps are typically thicker and heavier, insulated and scrim-reinforced to prevent tearing. They're also specifically designed for use as an enclosure system, which means they can be easily installed using built-in connectors that lock the tarps together.

Ensuring the tarps are locked together securely is key to the longevity of the enclosure. These systems may seem strong, but constant exposure to the wind can still rip a tarp to shreds.

"What you want to avoid with a winter enclosure is flutter," Haig says. "Once the tarps start flapping, they will destroy themselves."

Everything comes down to installation. It doesn't matter if you've purchased a cheap tarp or a top-of-the-line enclosure system unless you put the effort into setting it up correctly.
"There are guys who just throw them up and hope that it works," says Michael Corbett, regional sales manager for Layfield Environmental Systems. "It all depends on the seams when you're putting them together."

Gendall has also seen careless contractors do damage during installation.

"They do it quick and easy and they poke tie wires through the side. What you've done is you're starting to rip the fabric," he says. "The basic thing is taking the time to install it properly."

One rip or loose seam and the enclosure can easily be pulled apart by the wind. Unless it's securely fastened, you can wave that tarp goodbye. And most likely, it will wave right back.

Of course, there's wind and then there's wind. On a blustery day, a securely fastened tarp could easily turn your scaffold into a rather shaky ship attached to a giant orange sail.

For that reason alone, many of the higher-end enclosures are built so that their connectors-which could be anything from bungee cords to tie wires to pins-release once the wind hits a certain speed.

For example, Corbett says that when Layfield's WeatherPro tension enclosure system is buffeted by winds exceeding 80 kilometres an hour, it is designed so that "it will just give away rather than take the whole scaffolding down."

One of the most vital safety features, however, is one easily taken for granted: resistance to flame. As Corbett points out, that's one thing contractors should never assume.

"They've given me calls, saying, ‘What the heck? [The tarp] went up in flames!'" he says. "Well, that's because it's not flame resistant. But for whatever reason, a lot of people believe that it is."

That overconfidence can lead people into big trouble. Anyone using a cold-weather enclosure to protect workers will almost certainly be using it with some sort of heater. In those cases, safety precautions are a must. "Whenever there's heat around, they should be using flame-retardant materials," Haig says.

He explains that his company only sells flame-retardant enclosures. The additional cost is minor in Haig's eyes. "It's about another 10 or 15 per cent over the price of the product, but it really is a safety issue."

A well-sealed enclosure, when combined with a heater, can easily maintain a comfortable work environment at even 40 below. But there is such a thing as being too efficient for your own good sometimes.

Corbett has seen tarps destroyed not only by the elements, but also by workers who find the enclosure just a tad too snug for their liking.

"They'll take their knife and cut a window into the tarp," he says, laughing. "If it's getting too warm, wouldn't you just turn off the heat?"

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