 Air Barriers control the unintended movement of air into and out of a building enclosure.
Air barrier systems are made up of a number of materials which are assembled together to provide a complete and total barrier to air leakage. The building enclosure includes all walls, roofs and floors of the building and can include connected parts or separations within a building.
The air barrier system essentially “wraps” the building shell and ensures that it protects the building from air leakage and its adverse affects. These effects can range from energy, mold, occupant discomfort and more. They can also reduce the life span of a building.
A properly functioning air barrier system provides a barrier against both the air leakage and the diffusion of air caused by weather, wind, stack and mechanical equipment pressures.
Spray Foam Insulated Air Barrier Systems are fully-adhered, providing a seamless, monolithic air barrier that conforms to irregular shapes, slopes and allows easy detailing around penetrations such as pipes, windows, doors and sheathing fasteners. SPF air barriers contribute to improved building durability, energy efficiency, and to occupant comfort, health and safety.
Not only does SPF provide the highest level of thermal insulation, it provides a monolithic, fully sealed air and moisture barrier. Its spray applied installation process speeds construction and reduces labor costs substantially.
Alternate air barrier systems such as sheet goods require a great deal more labor for installation. Sheet goods do not possess the insulation (R-value) characteristics and are often susceptible to tears, and air leaks due to their reliance on proper seeming, adhesion and interface with the building’s façade.
For the occupants to be comfortable, we condition the air in buildings. In summer or in cooling climates, we normally cool and dehumidify the air to a lower temperature and humidity that the exterior environment. In winter or heating climates, we normally heat and humidify the air to a higher temperature and humidity than the exterior.
An air barrier assembly is a collection of air barrier materials and air barrier components assembled together in a specific manner. A wall air barrier assembly would include the main air barrier material and then use additional materials and components to join the air barrier materials together. The performance of a total air barrier assembly is far more important than the air permeance of the material itself.
When conditioned air (heated, cooled or filtered) leaks out of a building, and unconditioned air leaks into a building, additional energy is consumed to re-condition the remaining air. Air leakage can result in increased energy consumption costs of up to 30%-40% in heating climates and 10-15% in cooling costs.
Buildings which have a properly installed air barrier system can operate with smaller HVAC systems since they do not have to compensate for a leaky building. In many cases, the reduction in mechanical equipment size and cost can offset the cost of the air barrier system.
Air barrier systems also provide a barrier to pollutants and other contaminants entering the building or the building enclosure. Water vapor, suspended particulates, dust, insects, odors/smells, are all contaminants we want to keep out of the building. Water vapors that leak into the building (from the inside in heating climates and from the outside in cooling climates) can condensate and forms liquid water a key ingredient to corrosion and the potential development of mold.
Air Barrier Testing
The testing of an air barrier assembly for air leakage is done in accordance with ASTM E 2357. The results will include the air permeance of the material (the amount of air that passes through the material) the air permeance of the components and the air leakage that results from joining all the pieces together. The air leakage of the air barrier assembly is not to exceed 0.2L/(s•m2) @ 75Pa. (0.004 cfm/ft2 @ 1.57 psf)
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