Some Halifax buildings cause wind tunnels that make it hard for pedestrians to walk upright, but architects say building designers have more important things to consider.
By Jamie Lee with files from Andrea Klassen <firstname.lastname@example.org>
Posted: Nov. 15, 2007
Halifax is a windy city. Browse the photo gallery to see how wind makes for work and play. All photos: Andrea Klassen
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When people walk by the Maritime Centre, they brace themselves for the strong winds bearing down in their path.
“It’s unfortunate it’s there in the first place,” says Greg Fry from Fowler Bauld & Mitchell Architecture in Halifax.
The 19-storey downtown Halifax building is notorious for creating a strong wind tunnel that blows pedestrians off their feet.
Fry says strong winds like these can be dangerous to pedestrians, especially when it’s icy and people can slip and fall.
Still, he adds, architects don’t take wind force into consideration as much as they should when designing buildings. There are more important factors for architects to consider, so pedestrian-level wind isn’t a priority.
Brian Lilley explains that wind tunnels are created when a building is built in the path of the wind. The building acts as a wall, pushing about half the wind that hits it toward the ground. Lilley is an architecture professor at Dalhousie University.
He agrees wind is an important factor to consider when designing buildings because of its effect on pedestrians. Sharp wind “actually makes for a very mean environment,” he says, especially in winter, when temperatures drop.
According Hanquing Wu, a building’s height, orientation and shape all affect wind speed.
Wu, a consultant at Rowan Williams Davies & Irwin Inc., says his firm looks at gust wind speed, which is the speed of high winds that only last a few seconds. The company is a wind engineering consulting firm based in Guelph, Ont. Wu also specializes in studying pedestrian safety and comfort.
Wu says people’s tolerance of the wind changes with the activity they’re doing. “Sometimes people are there to read the newspaper and drink coffee, and it requires very low wind speed [to be comfortable],” he explains. “If people just walk from A to B, then they can tolerate a little bit higher wind speed,” he says.
There is a wind speed limit where the wind becomes dangerous for pedestrians. “If the wind’s so strong it can knock you off your feet, then that would be too much, no matter what activity is planned for that place,” says Wu. He says that limit is usually when wind reaches 88 km/h, which occurs a few times a year in Halifax.
But wind tests aren’t often done, says Fry, because they come with a hefty price tag. They cost around $30,000, which he says is still a high percentage of the cost of a $1-million building. “Is there a benefit to doing wind testing? Not that the client can see,” he adds, especially when buildings can be fixed accordingly after it has been built.
There are several solutions for wind tunnels created by buildings. Owners can decide to add canopies and terraces around the entrances to divert the wind. They can also plant coniferous trees that stay bushy year-round to block winds from the doorways. Arcades – a tunnel-like archway alongside the base of the building – can also allow pedestrians to walk unhindered.
To plan for wind in the design process would, for example, mean designing the building to sit on top of a podium-like structure where wind is diverted at the top of the podium, leaving passersby to walk unhindered at the base of the podium.
But developers and other clients want to maximize their return on constructing a building, agrees Lilley. “If [the developer] can get away with not doing wind tunnel tests then obviously it’s like an extra expense to him,” he says.
They’re also mainly focused on maximizing the space they have, Lilley adds. And other players in the design process are occupied with other goals that are often thought to be more important than wind effects.
For example, architects are mainly concerned with the design of the building as well as the materials they want to use to build it.
“The city is just really trying to make sure that nothing falls apart and hurts anybody,” he adds.
Fry agrees. Because factors like designing fire escape routes are so much more important, considerations for wind effects will always be an afterthought.