What Is a Roof System Air Barrier?

Roof Systems

• The term "roof system" applies to the design of any roof and its interconnected elements. For instance, a sloped roof designed to deflect snow with air vents for heating and cooling systems and an incorporated chimney constitutes a roof system for a cold climate with heavy snowfall. The elements of a roof system vary depending upon the shape of the roof -- flat, gently sloped, sharply sloped, etc. -- the size of the building and the elements affecting roof construction, including vents, gutters, drains, roof materials, air barriers, climate and more.

Air Barrier

• An air barrier refers to a system used in building design and construction to control airflow and the affects of outside air on a building’s internal environment. The term "air barrier" sometimes refers to an actual buffer used in construction to prevent outside air from entering a building’s environment. However, air barrier systems also incorporate elements like windows, doors, vents, insulation and all the things used on building materials to prevent the penetration of moisture and air, such as caulking, sealants, membranes and coatings.

Roof System Air Barrier

• A roof system air barrier refers to one of two things. The term may indicate all the elements of a building’s air barrier located on a roof, including vents, windows, sealants, insulation and more. Or, it may refer to a specific element of the air barriers found in roofs. Known as a roof membrane, the roof air barrier assumes the form of a sealed layer placed on the underside of a roof. This layer traps air coming into a building and helps it leave the building without infiltrating the environment within the building.

What Air Barriers Do

• Basically, air barriers exist to prevent air leakage, or the process by which outside air seeps into a building. Air leakage helps moisture infiltrate buildings, which can lead to the development and spread of mold spores, as well as cracks and other faults in concrete surfaces such as walls and foundations.. Air from outside a building also brings in undesirable elements such as allergens. Such air places a strain on heating and cooling (HVAC) systems by upsetting temperature balance. The strain on HVAC systems can lead to wasted energy, increased carbon emissions and more costly heating and cooling bills.