Leaky windows

Go to http://www.nrc-cnrc.gc.ca/eng/ibp/irc/ctus/ctus-n76.html to see a NRC report on Window Sill Details for Effective Drainage of Water.


In the 2000-2003 period, I believe, CMHC published 4 large ring binders of proven flashing details for various constructions…quite impressive. The above detail is a good one…now to get it in use in the field!!!

Dig a little further and you can find a “bunch” of free publications such as Construction Building Digests, Building Practices Notes, etc.



I have used them as background references for my Building science course for home inspectors.

In addition CMHC has a number of good “Best Practice Guides in Building Technology”. The prices vary - some around the $80 - $90 range.


Have a look at the last 2 lines of #9 by Gus Handegord. In Sept/1960, he says vapour barriers should be **sealed **to make them effective. This is a gent from the “old guard” at Canada’s NRC, Division of Building Research that mentored/helped Joe Lstiburek.

I was lucky to have found this free building science series in 1977, my first year working in energy conservation.

I subscribed to the “building Digest” from the NRC way back in 1965. Flashing methods that were used worked. For some reason they stopped installing the flashing.
Another problem is the current code calls for the flanged window to be embedded in mastic around the window opening. The builders are not even using the mastic properly and not installing flashing compounds the problem. The code inspectors are not catching it or enforcing the code, hence all the leaky windows. The second source of leaky windows is not a leak but condensation on the cold plastic frame next to the outside because the builders are not sealing the vapour barrier to the inside edge of the window frame. The Alberta government has been studying this problem for over two years as they stated on the “Primetme” TV show that yours truly was on last years summer and still nothing has been done about this problem.
It’s costing property owners millions across Canada.