Masonry Magazine January 2011 Page. 34
AIR BARRIERS AND INSULATION
These products provide excellent self-sealing characteristics for penetrations. The sheet materials also can span a somewhat larger gap, which can be advantageous when covering sheathing boards if the seams have not been treated in some way. The large majority of self-adhesive sheet systems also are considered to be a vapor barrier in addition to an air barrier.
All air barriers must be totally continuous. That leads us to one of the major debates that continue within our industry: "breathable" or "non-breathable." Some believe all wall systems should be able to breathe and allow vapor transmission through the wall assembly, while others still believe northern climate wall systems with outboard rigid insulation should incorporate a complete air and vapor barrier system. The breathable air barrier actually does not have a specific location within the wall assembly and, in many cases, ease of an effective installation may determine its location. In most cases, no matter the type of barrier system used, the normal placement is on the outer face of CMU or exterior sheathing, which provides the optimum location to create a totally complete and continuous barrier.
As energy efficiency becomes a larger issue, designers and contractors are confronted with more difficult questions regarding air/vapor barriers, detail tapes and flashings, insulation types, sealants, windows and door units, roofing systems, anchoring systems, and mechanical penetrations and their effect on the building envelope. Sound complicated? It sure is, and today, having trusted consultants and industry resource people is becoming more necessary. One thing we all have in common is the desire to create a complete building envelope that functions and performs as intended.
Chris Bupp is architectural and educational services director for Hohmann and Barnard.
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