Air barriers control air leakage into and out of the building envelope. Air barrier products may take several forms: *Mechanically-attached

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

s, also known as housewraps, usually a

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

-fiber or spun-bonded

polyolefin A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...

, such as Tyvek is a generally accepted moisture barrier and an air barrier (

ASTM ASTM International, formerly known as American Society for Testing and Materials, is a standards organization that develops and publishes voluntary consensus technical international standards for a wide range of materials, products, systems and s ...

E2178). *Self-adhered membranes, which are typically also a water-resistant barrier and a vapor barrier *Fluid-applied membranes, such as heavy-bodied paints or coatings including

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

ic based and asphaltic based materials *Closed-cell medium density spray-applied

polyurethane Polyurethane (; often abbreviated PUR and PU) is a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane term ...

foam, which typically provides insulation as well *Some open-cell spray-applied

foam that are of high density *Boardstock, which includes 12 mm plywood or OSB, 25 mm extruded polystyrene, etc. Air barriers are divided into air barrier materials, air barrier accessories, air barrier components, air barrier assemblies and air barrier systems. Air barrier materials – Building materials that are designed and constructed to provide the principal plane of airtightness through an environmental separator, which has an air permeance rate no greater than 0.02 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with

E 2178. Air barrier materials meet the requirements of the CAN/ULC S741 Air Barrier Material Specification. The air barrier materials are typically the "big" pieces of material used in an air barrier assembly. Air barrier accessories – Products designated to maintain air tightness between air barrier materials, assemblies and components, to fasten them to the structure of the building, or both (e.g., sealants, tapes, backer rods, transition membranes, nails/washers, ties, clips, staples, strapping, primers) and which has an air permeance rate no greater than 0.02 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with

E 2178. Air barrier components are used to connect and seal air barrier materials and/or air barrier assemblies together. Air barrier components – Pre-manufactured elements such as windows, doors and service elements that are installed in the environmental separator and sealed by air barrier accessories and which have an air leakage rate no greater than 0.20 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with

E 2357. Air barrier assemblies – Combinations of air barrier materials and air barrier accessories that are designated and designed within the environmental separator to act as a continuous barrier to the movement of air through the environmental separator and which has an air leakage rate no greater than 0.20 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with

E 2357. Air barrier systems – Combinations of air barrier assemblies and air barrier components, connected by air barrier accessories, that are designed to provide a continuous barrier to the movement of air through an environmental separator, which has an air leakage rate no greater than 2.00 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with ASTM E 779 or CAN/CGSB 149.10 or CAN/CGSB 149.15.

Air barriers and water vapor

Some air barriers may be

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

permeable, while others perform the function of a vapour barrier. This is because water fits through narrower pores than the other main constituents of air,

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

(O2) and

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

References

External links

Air Barrier Design

Air Barrier Association of America

National Air Barrier Association (Canadian)

U.S. Markets Seeking Air Barrier Expertise
{{HVAC Building technology Building engineering Heating, ventilation, and air conditioning

Air barriers and water vapor

See also

References

External links