Photo courtesy Pella

Sun, wind, rain, snow — it just doesn’t matter. Because a French door gets installed where the view is, regardless of weather conditions. Fortunately, manufacturers have spent the 50 or so years that pre-assembled patio doors have been on the market figuring out how to build some pretty airtight units.

In fact, if a patio door from one of the major door and window companies leaks at all, chances are that the fault lies with the installation — not the door. Gene Summy of TLS Laboratories, a window and door testing company in Laguna Niguel, Calif., says the single biggest factor in door performance is how well it was installed. “Most...

or Register to read the full article.