The Purpose and Characteristics of a High Performance Air Barrier
Building tenants are understandably concerned over the quality of the interior space that they occupy. The comfort and integrity of the building will be enhanced if a high performance air barrier is incorporated in the building envelope.
A good air barrier provides a separation between the conditioned interior space of the building and the uncontrolled outside air. Air barriers can be constructed with rigid sheathing materials, including gypsum board, plywood, or rigid polystyrene sheathing, but these can be difficult to detail. Flexible materials can be used to create a good air barrier if cracks, joints, and seams are filled. If an installer is using a flexible material to create an air barrier, he should use one continuous piece of that material to cover an entire space, and all gaps between the material and any support joists should be sealed with flexible caulk.
A high performance air barrier will have these four characteristics at least:
- It will be impervious to airflow.
- It will be continuous over an entire building or over the space that it is intended to contain. Partial air barriers have limited to no effectiveness.
- It will be able to withstand forces that are placed on the air barrier both during and after construction of the building. This includes deflection of building materials from increased loads as building construction continues and forces of weather and other environmental factors when the building is certified for occupancy.
- It will be durable over the expected life of the building. Durability and expected life are relative concepts, but with routine maintenance and care, air barriers should not need extensive repairs or replacements at any time while the building is used and occupied.
The impervious nature of an air barrier is best understood with an analogy to a vacuum seal bottle. A sealed air space surrounds the fluid inside the bottle, which allows that fluid to maintain its hot or cold temperature for a longer period of time. When the vacuum seal breaks, the fluid’s temperature quickly settles to match ambient air temperatures. When used in combination with a good thermal barrier, a well-constructed air barrier, will keep the tenant’s space at a more constant temperature without excessive air-conditioning or heating. This reduces tenant and building utility costs as well as costs of maintaining heating and cooling equipment.
Air barriers also control moisture penetration between spaces, which limits mold growth, and provide a first layer of defense against fire and smoke from an adjoining space. Most air barriers are Class A Fire rated according to ASTM E86, but due to the plastic nature of the material, they will ultimately burn. Building engineers who are designing air barrier systems should check local building codes to determine required fire resistance ratings for commercial buildings in the area in which the construction is occurring. Air barrier standards by themselves may not be sufficient to satisfy fire codes, and additional separations and safety considerations may be required to meet those codes.
Tenants are increasingly looking for environmentally friendly buildings that minimize their operating costs while providing an inviting space that reflects the nature of their businesses. Buildings with high performance air barriers are higher on the “green” scale and provide benefits that a tenant will implicitly appreciate even if they do not realize their importance. When you are designing or erecting any new building, do not discount the value of a proper air barrier in your construction planning.
Cosella-Dörken delivers innovative, high-performance air and moisture barriers for commercial and residential construction sold under the DELTA® brand name. A North American manufacturer based out of Beamsville, Ontario, Cosella-Dörken Products, Inc. is a subsidiary of Ewald Dörken AG, a leading European developer and manufacturer of waterproofing and drainage products sold worldwide. Cosella-Dörken is known for delivering premium products while providing educational programs and full technical support. For more information, call 1-888-4DELTA4 (433-5824) or visit www.cosella-dorken.com.