The Importance of a Proper Vapor Barrier

Most builders and contractors know that a vapor barrier is necessary to prevent water vapor from passing through interior walls by way of diffusion. Like other trade specific practices it is conceptually simple, but to properly execute is a different matter in and of itself. As they say, “the devil is in the details”. That saying rings true the most when it comes to construction projects. The best materials become worthless when the application is substandard. I have seen this all too often. While there is a point of being too perfect, there is also practical methods that can be applied to create a successful end result. When it comes to vapor barrier, the industry standards in Southcentral Alaska are to use a 6mil. polyethylene sheet installed to the studs after insulating on

the warm wall side. The polyethylene has a perm rating of .06 which allows almost no moisture to penetrate through the sheet itself. Sounds good right? Install the vapor barrier and you’re good to go. Wait, what about seams? What about terminations? What about electrical boxes, transitions, bunching, and other obstacles? What about the holes made with the installation of drywall or other wall coverings? Are your wheels turning now? These details are not necessarily spelled out in a contract. You may see verbiage that says “Installed per code” or “Installed in accordance to manufacturers’ specifications” or even “Installed per industry standards”. What does this all mean though? It does not specifically say to seal all above mentioned areas. It does not give any notice to the fact that drywall screws penetrate the vapor barrier upon installation. So where does this all leave you? This is why it is important to choose a company that wants to achieve more than the absolute minimum. If you break it down, that is exactly what code is...the absolute minimum required. Look at these photos below to see the importance of going above and beyond the minimum. Aside from obvious physical damage, take a moment to think about indoor air quality and your families‘ health.

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