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Building sciences professor John Straube speaks to CSC Canada conference
Windows and energy savings:
The weakest link in Canadian buildings
John Straube
Canadian Design and Construction Report staff writer
Where is the weakest point in energy savings in Cana-
dian buildings?
John Straube, a University of Waterloo engineering
professor, indicates that windows, even ones marketed
for their high-efficiency – leak energy at an incredible
rate, and less-than-perfect fenestration solutions could
defeat other energy-saving efforts, including wall and
ceiling insulation.
“What's really damning is that older buildings, built
well before the Second World War, are pretty good in
terms of energy consumption,” he told the annual Con-
struction Specifications Canada (CSC) conference in
Kitchener in May. As an example, the university's School
of Architecture building, constructed in the early 1920s,
uses “significantly less energy than the average.”
“The walls are made of solid masonry,” he said.
“There are decent windows – but not too many of them.”
Yet the building is “filled with natural daylight.”
Compare this construction to modern, mass-market
urban condos in Toronto, with floor-to-ceiling glass cur-
tain wall facades.
These may look nice, and help sell the condos, but
the owners will be stuck with the energy bills – and pos-
sibly hefty maintenance charges – for years and years.
Straube, in an earlier CBC interview, said a building is
a living, breathing thing, enclosing and protecting the
people who live inside. “Building with glass walls is to
miss the main point of a building . . . sacrificing the pro-
12 – Summer 2014 — The Canadian Design and Construction Report
tection that is a building's first duty for a beauty that is
only skin deep,” CBC reported.
“It's almost derogatory in my world to forget about
everything else that's part of experiencing a building,”
Straube was quoted as saying. “I like to think what is
the building going to be like on a dark and stormy night.
In our climate, particularly, we care about that. It's life
and death.”
Simply put, he told the national CSC conference,
many commercial buildings have really “poor enclo-
sures” with exceptionally low insulation R-values, caused
by “too much glazing, too many thermal bridges, and too
much air leakage – which no one seems to measure.”
Meanwhile, heating and ventilation systems have
been designed with super-efficient equipment, but “the
systems are often very inefficient.”
The result, windows, even with double-glazing, often
have absurdly low R-values, perhaps at 2 or maybe 3.
If these window systems dominate the building, even
the best insulation within the walls won't do much to
solve the problem as thermal bridging gobbles up wall
and ceiling insulation value.
For example, if wall systems have an R20 level (over
50 per cent of the area), and there are R2 windows cov-
ering the other 50 per cent, the overall building insulation
value is just R3.6.
Assuming really good windows are installed, with an
R4 value, then the building gains some ground, but the
overall insulation factor remains what would seem to be
a dismally low R6.6.