A crash course in air barriers
The basics about air barriers
Air barriers are mandatory requirements in four codes and standards (ASHRAE 90.1-2010, ASHRAE 189.1-11, 2012 IECC and 2012 IgCC) and have become code requirements through the adoption of these codes and standards or through building or energy code requirements in a minimum of 12 United States. In Canada, air barrier systems are requirements of the National Building Code of Canada (NBCC), and a requirement in all provinces and territories. Design professionals have worked hard and have come a long way to ensure air barriers are designed continuously across the entire building.
The different types of air barrier materials and their technologies have greatly increased in the last 20 years, giving Air Barrier Association of America (ABAA)-Certified Air Barrier Installers options for many different materials with which to work. Due to the nature of air barrier materials, masonry preparation is extremely critical to ensuring the material is installed properly.
Benefits of air barriersBy designing and installing a proper air barrier assembly, the entire building design and construction team will reduce conditioned air loss, saving a considerable amount of energy during the life of the building. By installing a properly designed air barrier assembly, you are reducing chances for building enclosure failures as there will be less chance for condensation in the building enclosure caused by air leakage. The air barrier assists in keeping bulk water that has made it was passed the cladding from entering the building enclosure. By reducing air leakage and associated drafts, occupants are more comfortable.
Air barrier continuityAir barriers are important in buildings, though architects need to be diligent when designing them. Factors such as ambient environment and building use need to be considered during the design phase. Engineers need to ensure they’ve looked at the strength and durability of each kind material, based on service loads of the building. It is critical that air barriers are designed continuously on sides of the building, ensuring penetrations are transitioned and sealed with all materials being installed in a shingle fashion down the wall.
The most common areas where continuity is critical and is a major source of air leakage is at the wall-to-roof connection, and wall-to-window and -door openings. Air barrier contractors need to ensure the air barrier is installed continuously and, if there are questions, they should clarify with the design professional.
Who is installing air barriers?We see all types of trades joining the ABAA to become accredited to work on our projects, including masons, insulating contractors, waterproofers, drywallers, roofing contractors and cladders. We see many masons getting certified and completing a majority of ABAA projects. ABAA-certified air barrier installers are the best in the business, since they have the experience and the training that only ABAA can deliver to its clients.
Today’s progressive contractors are installing a wide range of building enclosure materials, which allows them to “own the wall.” By adding air barriers to the work that you already complete, you can offer better coordination of trades, increased quality of final wall assembly and increased profitability.
Types of air barrier materialsThere are many different types of air barriers on today’s market, including fluid-applied, self-adhered, mechanically fastened building wraps, spray polyurethane foam (SPF), (insulating) boardstock, flexible interior membranes and factory-bonded membranes to sheathing. Each of these materials has benefits to use within a building design and should be evaluated based on the design professional’s familiarity and proper cost analysis of each system.
Pre-cast concrete and masonry preparationThe preparation of masonry is critical to the installation of fluid-applied, self-adhered or SPF air barriers. Materials that adhered to the substrate (fluid-applied, self-adhered and SPF) need to be installed on substrates that are clean, dry, and free of contaminants that can affect the adhesion.
Air barrier installers need to be aware of the material requirements for installation and the manufacturer’s requirements for moisture content of the CMU or pre-cast concrete. Moisture content can be checked by using a moisture meter or with the plastic-sheet method described in ASTM D4263. When substrates have high moisture content, you may run the risk of having the material not adhere properly and/or moisture creating a bubble behind the material that may get trapped, forming voids and pockets. On the face of the building as well as building corners, all masonry corners should be tight, interlaced and secure, with no gaps or openings.
CMU blocks should have the joints tooled flush with the face of the block, and excess mortar knocked off. Brick ties have to be secure and have the mortar smooth around the tie. All blocks should be tight, secure and flush.
Pre-cast concrete shall be free of release agents from formwork as air barrier materials may not bond. A concrete slurry should fill in any voids, honeycombing or cold joints that are not flush on the pre-cast concrete or masonry to ensure the air barrier materials are well-bonded to it.
Air barrier installers have to be aware that each material has strict installation requirements. Self-adhered materials must be have primers installed correctly, rolled into place with a pressure roller (to make it free of air pockets) and have termination sealants installed. When installing fluid-applied materials, the installer needs to ensure the material is being applied at the manufacturer’s required thickness. Boardstock need to have the joints sealed to reduce air leakage, maintain plane of water tightness, and must have the specified fasteners installed at the spacing required by the manufacturer.
Designing a continuous air barrier assembly to be installed by an ABAA-Certified Air Barrier Installer has been recognized by the construction industry as assisting in meeting the goal of installing a top-quality air barrier assembly. By designing the air barrier assembly so that it is continuous, choosing the correct material for your project, properly preparing the substrate and installing the material correctly, we all ensure that we leave future generations an energy-efficient building stock free of problems.
Originally published in Masonry magazine.
About the Author
Colin Szewaga, C.E.T., is technical services advisor for the Air Barrier Association of America (ABAA).