18 January

Sometimes Being Thin Is a Bad Thing

In this week’s edition we are going to cover two things that are near and dear to my heart – quality AND quantity.  I know, I know…we have always been taught that  one can usually exist without the other.  I can still hear my parent’s advice when I was doing chores as a kid that it’s all about the quality and not the quantity of whatever I was doing.  For the purpose of this discussion, I can honestly say that they were wrong…kind of (just don’t tell them).  There is this trend going around in our industry that applying fluid applied air barriers at a thin mil thickness will suffice to prevent the permeance of air into a building.   As long as it passes ASTM E 2178 (Product Related Air Permeance Test) or ASTM E 2357 (Wall Assembly Air Permeance Test)  a thin mil air barrier will work, right?   Well, yes and no.  This is what I like to call the weekly “Mike, would you cut to the chase already?” moment. With respect to ASTM E 2178, a piece of 6 mil polyethylene plastic would work, but in real-world construction that just isn’t gonna happen.  Why you ask?  Poke a hole through it, blow air through the area and there’s your answer.  When we get to a more true- to- life mock-up as seen in the ASTM E 2357 test, the question becomes “How on earth is a thinner mil fluid applied air barrier going to traverse over the irregularities of CMU block or nicks and imperfections seen in exterior gypsum as well as roof to wall/wall to foundation transitions, pipe penetrations, brick ties and etc?”  This is not even taking into account that no installation is perfect and pesky nuisances such as pinholes and craters do happen – and when they do, what would protect the building better, an 8 mil or a 40 mil membrane?  The truth is,  if it looks like paint and is thin like paint, then it probably belongs on the walls of your kitchen and not on the exterior sheathing of a $10 Million medical building.  In the world of building envelopes, the “bare minimum” just doesn’t cut it anymore. Quality and quantity (a 40 dry mil fluid applied membrane- such as CCW’s Barritech VP or Barriseal- installed by a quality contractor will do) are the two words that should be ingrained in your brain when utilizing air barriers for your next new construction or restoration project. 

Questions? Arguments?  Would you like to share a great air barrier success story? Then email me at [email protected].

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