Canadian Consulting Engineer

Comment: The cold side of cheap glass walls

December 1, 2011
By Bronwen Parsons

Impressive programs for reducing greenhouse gas emissions are being carried out at campuses across Canada. Hundreds of millions of dollars has gone into developing green buildings and upgrading the existing building stock (page18).

Impressive programs for reducing greenhouse gas emissions are being carried out at campuses across Canada. Hundreds of millions of dollars has gone into developing green buildings and upgrading the existing building stock (page18).

An especially fascinating approach has been taken at the University of British Columbia. The new CIRS building collects heat from the roof of a poorly insulated building next door — energy that would otherwise go up to warm the heavens. Nancy Knight of UBC suggested that that this concept of networking buildings to circulate waste heat could be applied beyond universities into dense urban areas. Instead of retrofitting an older building’s envelope to be more efficient, it might make more economic sense to simply draw off the heat from the roof and recycle it.

Of course it would take hordes of lawyers and financial types to set up these kinds of arrangements between different owners. But if a developer owns lots of contiguous buildings, it is a feasible approach.

On the subject of energy seeping from building envelopes, questions are being asked in the media and among engineers about why we are building so many condominium towers with floor-to-ceiling glass walls. Toronto currently has 150 towers under construction, way more than any other city in North America.

The glass condos look beautiful and provide magnificent views from inside. Consequently they have huge market appeal. Units of just 700 square feet are going for $500,000 plus in the downtown. But most of these towers are essentially greenhouses. Young buyers might not be so quick to snap them up if they knew their energy and environmental costs.

Questions about why we are using so much glass began when some panes fell from new condos onto the city’s sidewalks this summer. Then in November the CBC radio show Metro Morning ran a series “Throwaway Buildings: the slow motion failure of Toronto’s glass condos.” The program, produced by Mary Wiens, suggested that some of these glass walls will need costly repairs in as few as 10-15 years.

Just as critical is the poor thermal performance of glass. Commercial office buildings and extremely high-end residential towers use carefully engineered curtain walls that aren’t usually a problem. However, many condominium towers are being constructed quickly with simpler “window walls” that rely heavily on sealants and caulking and have poor insulating values.

New York and other U.S. cities have a mandatory building energy labelling system that Canada would do well to adopt. Buildings over 50,000 square feet have to disclose their energy efficiency and have to be audited every 10 years. Some U.S. cities also have strict rules governing building quality.

When we buy a fridge we are given its energy rating. When we buy a car it’s our right to know how much gasoline it uses per kilometre. Investing in a condominium means not just investing in your own unit, but in the durability and energy efficiency of the entire building. Now why on earth shouldn’t someone investing their financial future not have the right to know how well the building performs? Bronwen Parsons



Bronwen Parsons


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