30,000 green building professionals are coming to Toronto for Greenbuild in October; this series will try to explain Toronto to them.
A hundred years ago, the walls of Toronto's stone and brick buildings probably had average R-value of 4; today, it has probably dropped to R-2. That's because all the developers love those floor to ceiling window walls that are quick, cheap and glitzy. They all use glass balcony guards as well; one barely needs an architect anymore, it is so formulaic.
But lately the formula has been breaking down, as glass guards have been spontaneously exploding, showering the streets below with sharp little sugar-cube sized pieces of tempered glass.
Image credit Allan Windows
Most of the failures have occurred at one building in midtown Toronto, where seven balcony guards exploded and fell to the street or onto the podium. The developer has now removed all of the tempered glass panels and is replacing them with laminated glass panels. The problem appears to be nickel sulphide inclusion, the "Achilles heel" of tempered glass. How do they know it is this and not just lousy installation? According to the Star, engineer Mark Brook, investigating the problem and looking for the tiny nickel sulphide nodules, got lucky:
It had been testing intact panels from the north tower of the Murano building as the developer took them down. One night, a pane resting against a wall in the testing facility exploded. They found their specific glass bit. "It's not poor installation," Brook said. "It's not wind, it's not the weather, it's these imperfections."
City Councillor Kristyn Wong-Tam is demanding action. She tells the National Post:
"I am very worried because I don't know how far reaching this is," the councillor says. "We have now had it in four towers in a short period of time. There could be impurities in the glass. Is it a production problem? This happened in buildings with different glass, different architects, different developers and different design. We need an investigation. This cannot take months."
But the problem is well known among engineers. According to a study by Dr John Barry, an Australian consultant,
More than 45 years has elapsed since the cause of spontaneous fracture in toughened glass was first established. Since then there have been a number of attempts to eliminate the problem.
He notes that there are a number of different ways to test the glass, but that they are expensive and time-consuming. Money and time are two things that condo developers try to minimize, so they buy cheaper tempered glass from the lowest bidder. Laminated glass has a plastic layer to hold it all together, but it costs more. End of story. National Post columnist Peter Kuitenbrouwer nails the real problem:
Our city is enjoying a condo-building frenzy unmatched, I would venture, in the history of any Canadian city. Perhaps it is time to slow the pace and build our city with more care.
More in this series:
Buildup to Greenbuild: A New Vision For The Toronto Waterfront
Buildup To Greenbuild: The Green Roofs of Toronto