My Window to the World Leaks

In my work I constantly see property damage either from "event" related damage or from poor original construction in the form of "construction defects".......now "latent defects". Either of these two categories will normally have water intrusion damages. The latent defect condition, created during construction, is the premise behind this article. The article's intent is to inform and educate the reader in basic categorical sources of water intrusion and specifically related to windows.

The building envelope is complex. In order to prevent and control water, moisture, and water vapor intrusion into the building, the building envelope system, and it has many components, must work as intended. The failure of the envelope, a single component in the envelope or combination of system failures can have devestating affects on the building and its inhabitants. The visual I like to use in illustrating this simple concept is the image of putting one screw all the way through the hull of a submarine. Maybe that's not a problem. If you have several and the bildge pump fails.........what happens next?

When discussing the topic of water intrusion from latent defects, I always break down the discussion into three basic components; the window itself, the installation of that window and the preparation of the window opening. 

No matter how many projects we see, in the wettest parts of the country, it seems clients, owners, insureds and even engineers make the same overly simplistic and incorrect generalized statement..."the windows leak". But.......do they?

That statement is too broad......too simplistic. When heard, one initially thinks there is actually a problem with the window. Just because there is water damage around the window doesn't necessarily mean that the window itself leaks. One can never know why water is entering the building envelope at the window opening unless one starts field testing and performing destructive analysis.

What we eventually find is that conditions generalized as "window leaks" could be from one or a combination of conditions. Each of these "conditions" is a defective component from either a manufacturing process or a human process. Each of these "defective" parts of the system, the manufacturing process or the human process can each have many layers of defects, commonly known as defect densities. For example, there are many reasons (defects) that may make a window from manufacturer "defective". There could be a frame defect, a sealant defect, an assembly defect....well... you get the idea. The same is true in the field when it comes to the installation of the window and the opening preparation. There are dozens of possible defects for each and so there are almost endless possibilities for combinations or causal relationships.   

I've started breaking down the window water intrusion analysis into three basic sources; the window, the installation of the window and the prepatation of the window opening. Water intrusion could be from one or a combination of any or all three of these potential failures.

To understand the concept clearly, it takes a good window installed correctly into a properly prepard opening to mimimize the potential for water to follow the natural path of least resistance and enter the building envelope.

When I explain this concept to attorneys, I try to just refer to the conditions as good or bad so they can relay that to a jury when the time arrives. Very simply, one could have a good window (defect free) incorrectly installed into a properly prepared opening. Now.....does the window itself leak? No....not really. In a court room that could be the difference between a product liability claim or a contractor claim. But, one can just as easily have a defective window perfectly installed into a properly installed opening. That's why field testing the product during installation is so critical.....but very few contractors ever take advantage of the ASTM provided guidance.

This problem, this analysis, boils down to simple math. Using fundamental combination theory, there are eight (8) possible generalized macro combinations of reasons why water is able to enter around the window and or window opening.

Since there are three defined categories of defects (window, installation and opening preparation), each with a simple good/bad condition, we wind up with a combination possibility result of 2X2X2=8.

In chart form, those combination possibilities look like this:

 

 The absolute worst of the possible combinations is a defective window installed incorrectly in a poorly prepared opening.

This DCD (defect combination density) can and will have catostrophic affects on wood framed structures. in the realitvely short time period of two years, wood framing can be rotted, even reaching the point of complete loss of structural integrity. The loss of structural integrity not only affects loading but wind shear as well. And I'm not stretching the truth when I tell you that I've poked my finger through the structural members of a building just two years old.

The water intrusion can also draw subterranean termites which will eat the structural framing. The water instrusion has created a conducive condition to termite infestation and the termite bond has been compromised. The abundance of water in locations over time can lead to brown cubical rot as well as the ability for wood decaying fungi to start eating the wood as well. For a visualization.............should OSB be see through?

There is one other direct result of water intrusion from the possible combination of just the window conditions alone and that is compromised indoor air quality. Water intrusion is the first Stage in this process with the compromised indoor air quality being Stage V......but that's another article.

In short.............you may not have a window problem at all. You may have an installation problem. Then again........you may have both. I will always ask you to prove it.