First it melted cars, now it’s blowing people over. One of London’s newest icons, the so-called ‘Walkie Talkie’ skyscraper is facing claims that its design is causing a troublesome wind tunnel effect down a major city thoroughfare.
The City of London Corporation is investigating an increase in the number of complaints about down-draughts at the base of the 160-metre skyscraper as powerful gusts of wind have seen workers blown over and signs knocked from buildings.
When the wind hits a tall building, it can be pushed down towards the pavement where it swirls around and creates wind tunnels. It’s called the Venturi Effect or downwash.
As buildings get higher, this vortex effect – as you have wind shedding off the sides of the buildings – creates small little vortices that then have the potential to cause problems at ground level.
Nada Piradeepan, an expert on wind properties at engineering consultancy firm Wintech, speaking to media in the UK said: "The downdraught effect is most strong where buildings stand face-on to the prevailing wind, which in London is from the south west.
"More rounded buildings, such as the Gherkin [another London icon], don't have quite the same downdraught effect and don't encourage an increase in wind speed around them, as the air doesn't accelerate around corners."
Tony Rofail, director at Windtech Consultants in Australia, who also have offices in the UK, agreed.
“It certainly does not help to have a sheer façade that goes straight to the ground for a building this tall,” he said.
Rofail believes the problems may stem from the type of instrumentation used in determining the potential effect of the wind.
“On inspection it appears that the treatments that were suggested are not effective given the stated conditions and the seasonal variations in the local climate,” he said.
The continued rise of the skyscraper across London’s skyline has led the City of London’s head of design, Gwyn Richards, to state that developers will be mandated to carry out more wind safety checks more often.
"The wind outcome at street level experienced post-construction on a number of projects differs somewhat to the conditions we were expecting from the one outlined in the planning application wind assessment,” he said.
But not all tall buildings create wind tunnels. Insetting the taller tower portion sufficiently from the road on top of a podium creates a windbreak which deflects the downward gusts away from street level.