Window Leaks
Rampant, Canadian Study Report
An intensive study of window performance
carried out by the Canada Mortgage and Housing Corporation
(CMHC) and the British Columbia provincial Homeowner
Protection Office (HPO) reported last winter that
most if not all windows are prone to significant water
leakage. Manufacturing, building design, installation,
and maintenance were all contributing factors: More
than half of new windows let water get past the operable
glazing in factory testing. In on-site quality control
inspections using a different test method, 35% to
48% of newly installed windows were found to leak
through the window unit itself, through joints between
the window and the rough opening, or both.
The passage of time, not surprisingly,
does not make leaks go away. After several years in
service, the incidence of leaks rose because of deterioration
and wear and tear. Windows in homes performed worse
than commercial windows: 100% of installed residential
windows examined after years in service were found
to leak either through the window unit itself or at
points of attachment to the building.
The report draws on data from only
a few hundred windows (all made in Canada), and the
authors did not identify any window brands. “There
are probably a thousand window manufacturers in Canada,
and the quality varies widely here as in the US,”
says Bob Maling, research and education director for
the Homeowner Protection Office. “But the observations
in that report apply to any company’s windows
in the US or Canada. Even the best made window could
be damaged during shipping or installation. So designers
today should take the approach that any window may
allow water through at some time, and you should design
the wall to handle that water.”