There is a book written by architects from Mill Valley, “Installation of Windows and Doors”, in the early 1990’s…it’s about 225 pages!! we have a lot to learn yet!! The above issues have been written about for years in various periodicals such as Energy Design Update, Journal of Light Construction, Solplan Review. It took about 30 years for any reference to rainscreens to appear in our codes (2004). There are examples from Quebec from the early 1970’s. The first document I have about “the rainscreen principle” (to stop/reduce the reverse vapour drive) was published in 1985 and cost a whole $4. The award should be taken off the architects wall!!! 4-5 years later the house has severe rot the pine clapboard siding and some sheathing were replaced. I worked on the first major example of “reverse vapor drive” in Nova Scotia in 1994/5- a house that won an award for the architect in 1989.If you check the permeance of all weather resistive barriers, you will find the highest (let’s vapour through the easiest) is TYVEK…and the vapour can flow both ways!!! The phenomenon of “reverse vapor drive” from sunlight heating the outer materials is now well accepted*. When water gets behind siding/trim and is held in place by surface forces such as being sandwiched between materials, a potential rot probelm begins. Some folks believe in ghosts, seances, re-incarnation, etc. The belief is that as long as the window is properly flashed / taped around same and a moisture resistant barrier has been installed, any water that would get behind the siding is negligible.
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