Throw-away Buildings & Thermal Window Failure: How it Happens: Virtually all glass condominium towers feature window wall systems (floor-to-ceiling walls of glass) enclosing the entire facade. Window walls yield spectacular views, but owners who buy a condo unit for the view may not realize that they're relying on a couple of panes of glass separated by less than an inch of insulated space to protect them from the elements. That insulated barrier will degrade over time, even as energy costs increase. On some buildings, five per cent of the thermal windows may have failed before they're even delivered to the construction site. Another 10 - 15 per cent will fail by the 20-year mark as they're exposed to the physics of heat expansion. By the 25 year-mark, a growing number will fail every year. Here's how it happens:
Insulating gas is sealed between glass panes: Insulated glazing technology, commonly known as double glazing, considerably improves the thermal efficiency of the window units used on older buildings. It consists of two and sometimes three panes of glass separated by a system of spacers and seals. It is that separation - not the glass - that provides the window with its primary insulating value.
The space between the panes is often filled with a heavy gas such as Argon or Krypton. Colourless and odorless, inert gasses don't easily allow air to pass through. In fact, Argon gas conducts 67% less heat than regular air, thus helping to keep building interiors cool during the day and warm at night. The seals that trap the gas between the panes of glass are clamped in place by aluminum frames which interlock with the adjacent frames, all of which are attached to the building itself.
Heat expansion damages seals: During the day, the sun's heat causes the exterior surface of the building to expand and contract while the interior surface remains relatively constant. Windows are designed with a certain amount of "give" to help withstand this uneven expansion. But over time, the continual expansion of the glass panes and aluminum frames puts stress on the window seals. The seals begin to break down.
Seals fail and gas escapes: As the window seals deteriorate, the inert gas that is responsible for most of the window's insulating value escapes from the window unit. Because the gas used in thermal windows is colourless and odourless, you won't be able to see that the window seal has failed. Building scientists can detect the failure by shining a laser beam through the window, and measuring the changes to the amount of light that emerges on the other side of the glass.
Although the escaping gas will change the window's thermal rating (from R-4 at the centre of the glass for a middle-of-the-road unit, to R-2.5 (R standing for thermal resistance), the more annoying problem will come as the window unit begins to fog up. Additional methods of analysing the thermal performance of windows are described in Mario D. Gonçalves and Robert Jutras' presentation at the 2007 Symposium on Building Envelope Technology. View Report [954KB .pdf]
Failed windows: The problems will be disguised for many years because the window frames are packed with desiccants - moisture-absorbing crystals. You've seen those tiny envelopes in the box for a new pair of shoes? It's the same principle - they help absorb moisture during shipping and storage. In the case of the window units, the aluminum frames are packed with strips of desiccant (circled left) to absorb water vapour. Desiccant plays a major role in keeping the glazing unit dry for the expected service life of the window unit. However, moisture entering through the seals will eventually overwhelm the desiccant, creating fog in what was once a dry space. You may not even realize your unit now requires more energy to heat and cool if the interior temperature is controlled by a thermostat. But you will certainly notice the foggy glass.
For owners who aren't aware that the expected service life of the window unit is a fraction of the life of the building as a whole, this may also be something of a surprise. For the first few years, the cost of replacing window units one at a time in individual condos will be annoying but not very expensive. However, at the 25-year point, as a growing number of window units fail, or if many of them fail earlier than expected, the condominium corporation will want to consider a complete replacement of the facade. Rising energy costs add pressure to make these changes to reduce the building's energy use.
For further reading on the choices that affect the service life of condominiums, see University of Toronto Professor of Building Science Ted Kesik's paper The Condo Conundrum.[250KB .pdf]
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| Residents of this Toronto condo at 81 Navy Wharf Court are suing the developer for alleged defects in the window wall system. |
Throw-away buildings: Toronto's glass condos - Many of the glass condominium towers filling up the Toronto skyline will fail 15 to 25 years after they’re built, perhaps even earlier, and will need retrofits costing millions of dollars, say some industry experts. Buyers drawn to glass-walled condos because of the price and spectacular views may soon find themselves grappling with major problems including:
- Insulation failures.
- Water leaks.
- Skyrocketing energy and maintenance costs.
- Declining resale potential.
Glass condominiums — known in the industry as window walls — have floor-to-ceiling glass, so essentially the window becomes the wall. Window walls generally span from the top of the concrete slab right to the bottom. One developer calls glass-walled condos “throw-away buildings” because of their short lifespan relative to buildings with walls made of concrete or brick.
“We believe that somewhere between, say, five and 15 [years], many, many of those units will fail,” said David House of Earth Development, which bills itself as a socially responsible property developer. House, who also has experience in the standard development industry, spoke to CBC as part of a special three-part series on the issue that starts Monday at 5 p.m. and 6 p.m. on CBC News Toronto.
No other city in North America is building as many condo towers as Toronto, where they have reshaped the skyline, overshadowed once-prominent buildings such as the Rogers Centre and, in many areas, blocked Lake Ontario from view. About 130 new towers are now under construction.
Not energy-efficient: Glass walls have been popular among developers and consumers alike because they’re cheaper than more traditional materials and make a good first impression. But they aren’t energy-efficient and come with a hidden price that could soar down the road, engineers say.
Floor-to-ceiling glass walls heat up and swell in the summer, freeze and contract in winter, and shift with the wind, engineers say. The insulating argon gas between the panes escapes, the seals are breached and the windows are rendered useless against the city’s weather. Eventually, the glass walls — the skin of these condo high rises — might have to be replaced entirely, with condo owners picking up their share of the multimillion-dollar costs. “Now is about when we should start seeing trouble with 1990s buildings, with the glass starting to get fogged up, the rubber gaskets and sealants starting to fail,” said John Straube, a building science engineer at the University of Waterloo.
Windows tempt buyers: The glass walls that undermine a condo’s durability and energy efficiency are a key part of the attraction when potential buyers first step into those sunlit spaces overlooking the city. “To walk in and see trees, and just to see the city — it’s a wonderful thing,” said Kamela Hurlbut during a recent tour of a condo with her husband, Jason. For first-time buyers like the Hurlbuts, who eventually hope to own a detached house, a condo also seems the only affordable home-ownership option. Their estate agent, Linda Pinizzotto, emphasizes long-term costs as she tries to warn the couple away from glass walls. “As time goes on, what they have to be concerned about are maintenance fees,” Pinizzotto said. “There’s certainly a lot more care and requirements in the building if they have floor-to-ceiling windows.”
Glass-walled condos meet the requirements of the Toronto building code, although the code does not specify how long a building should last. Energy-efficiency is also a fuzzy area, since condos aren’t rated that way. "We don’t have energy-efficiency ratings on condominiums and that’s too bad, because we get them on dishwashers, refrigerators, and they only cost a few hundred dollars,” said Ted Kesik, a professor of building science at the John H. Daniels faculty of architecture, landscape and design at the University of Toronto.
Janice Pynn, president of the Canadian Condo Institute, isn’t sure energy efficiency is a big factor for condo buyers initially — even for buyers who care about not wasting energy. “People talk that they want it, but when it comes down to what it's going to cost them, it doesn't even come into the equation,” says Pynn, whose Simerra Property Management company manages 250 condos across the GTA. “It really is ‘Can I afford to buy this?’ not 'What am I willing to pay to have a green building, or a building in the long term, that will be far more economical, and cost-saving and for the environment?' They're just not asking those questions.”
Toronto may be leading all cities in North America for building condos but its boom could soon turn to crisis. CBC Toronto has produced an investigation into what it calls "throwaway condos" - in reference to the floor-to-ceiling glass windows, which may fail 15 to 25 years after they are built. Given Toronto's massive condo stock, that could equal a lot of failures. In simple terms, the glass window doubles as the outer wall of each unit. While it may make the building look sleek and modern from the outside, what's going on inside is cause for concern - due mostly to Toronto's seasons and temperature changes.
The freeze-thaw cycle that occurs in Toronto (and other Canadian cities who are erecting similar buildings) will eventually cause the sealant in the windows to fail, resulting in more hot & cool air getting into each unit. Condo residents will then have to crank up the heat or air conditioning to keep pace, resulting in higher energy bills. (Check out this graphic that explains how the failure happens). Its not just the higher energy bills that owners will be stuck with - "window-walls" cost a lot more to maintain than traditional building materials in the long run and these owners will be picking up a huge maintenance tab 20-25 years down the road, according to John Straube, a building science consultant and professor in the Department of Civil Engineering and School of Architecture at the University of Waterloo.
"We have a hard time," says Straube, "thinking five years when we buy a laptop, ten years when we buy a car. With these buildings — both the skin and the mechanical systems are going to have to be redone in a 25-year time frame. The concrete structure will be there a long time but in 20, 25 years time, we are going to see a lot of scaffolding on the outside of the buildings as we replace the glazing, sealants and the glass itself." Vancouver has had its own issues with leaky condominiums given its weather but with Toronto taking the lead in condo building and cities with similar climates like Ottawa, Montreal, Halifax and Calgary following suit, condo dwellers can expect energy and maintenance costs to skyrocket, all for the sake of living in a building that has style over substance.
