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Why Should I Care About Moisture Management?

Why Should I Care About Moisture Management?

By Karl Feucht – Market Development Manager, Benjamin Obdyke, Inc

“Moisture Management” — this sounds like an exciting topic to bring up at your next Zoom happy hour, doesn’t it? Be warned; breaching that topic over a cocktail does not exactly lend itself to “life of the party” status. This is a lesson I may have learned the hard way.

Moisture management is a bit of a buzzword in the building industry these days, but why? What does it mean, and why should we pay attention? Is it really all that important, or is it just another trend that will eventually go by the wayside? Why don’t the building practices of yesteryear suffice when it comes to moisture management?

I live in a Lancaster County, PA, farmhouse that was built around 1900. Back when my home was built, construction methods were very different than today. Most of the changes over the past century have been very positive with the advent of new building materials, stricter building codes and more innovative designs. One notable difference that has had both a positive and negative impact is the lack of insulation that was used in the wall assembly and the virtual absence of air sealing that was done when my home was built 120 years ago. While this antiquated approach provides some notable drawbacks such as energy inefficiency and less comfortable living spaces, this method of construction was very positive in that it allows consistent airflow through the wall assembly. Moisture issues were not a problem in the homes of 120 years ago, or even 40-50 years ago, because homes could BREATHE. If moisture got behind the cladding (which it always does!), it was not as much of an issue because homes could naturally breathe and allow that moisture to escape. My home is far from tight and certainly is not the coziest in the winter, but we do not have any moisture issues in our home.

Fast forward to today and building practices have changed tremendously. We are now focused on building highly energy efficient homes. We are dense packing the stud cavities on the interior wall, adding rigid foam insulation to the sheathing on the exterior wall, and air sealing every possible crack and opening that may exist to prevent air infiltration. There is also a growing trend to building passive houses and net zero homes, which are both environmentally friendly and provide very comfortable living spaces. This is a great method of construction, but potentially creates a major problem in terms of moisture management because structures are simply built so tight that they cannot breathe and allow the moisture to escape the wall assembly. We have seen many structural failures of homes built in the last 10-15 years due to structural rot, mold, and mildew. Why is this? Are we taking two steps forward but one step back?

Dr. Joseph Lstibrurek, leading building scientist at Building Science Corporation in Westford, MA, has said that there are really two rules of moisture management: “Keep water out; let water out when it gets in.” This may seem like a contradictory sentence, but it provides a lot of wisdom for us as we are designing buildings today. It is vital to understand that the primary role of exterior cladding is aesthetic—the siding that is specified and installed on our projects is not intended to be the primary weather barrier for the structure itself. Many of the exterior claddings that are used today are considered reservoir materials—they actually absorb water and introduce more moisture into the wall assembly. This is a surprise to many. While there are some exterior claddings that are more effective in keeping moisture out of the wall assembly, it has never been more important for us to design buildings under the assumption that water WILL get behind the cladding.

So, the big question is this: when moisture gets into the wall assembly (and it will!), how do you manage it? How do you prevent that moisture between the cladding and the sheathing from becoming a serious issue or concern and leading to mold, mildew, rot and premature structural failure? The answer lies in that exciting term that you do not want to bring up at your next family dinner for risk of putting everyone to sleep: “Moisture Management.”

Moisture management is a complex topic; I am not going to solve all the issues or even provide a condensed CliffsNotes version in this brief article. There are a wide variety of factors involved in properly managing moisture behind exterior cladding, and sometimes the solutions are as varied as the building designs themselves. But the importance of moisture management has never been greater. And as building codes catch up to the stricter energy codes, we are going to see more importance placed on proper moisture management practices than ever before. This is not a fad or a trend—moisture management is a crucial component of good building practices and it is only going to become more important in the years to come.

There are many ways to provide proper moisture management behind exterior cladding. These range from older methods such as furring strips, to more modern building materials such as drainable house wraps and manufactured rainscreen products. Many manufacturers are also starting to provide products that manage moisture while also providing an air barrier. The important factor is to allow some type of gap between the sheathing and the cladding to allow moisture to drain and also add continuous air flow. This allows moisture to exit the wall cavity and for drying to take place. Proper window flashing details are of utmost importance as well.

Codes, technologies, building materials and industry trends are changing all the time; we must make sure that our building practices are keeping up. We must stay educated and vigilant to ensure that we are building healthy and sound structures that stand the test of time.

Karl Feucht covers the Mid-Atlantic region for Benjamin Obdyke and can be reached at [email protected]. Benjamin Obdyke has been on the forefront of moisture management since 1868 and is based in Horsham, Pennsylvania.

Benjamin Obdyke is an Allied Member of AIA Potomac Valley.

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