Air barrier
Encyclopedia
Air barriers control air leakage into and out of the building envelope
. Air barrier products may take several forms:
Air barriers are divided into air barrier materials, air barrier accessories, air barrier components, air barrier assemblies and air barrier systems.
Air barrier material – Building material that is designed and constructed to provide the principal plane of airtightness through the environmental separator 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 ASTM 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 accessory – 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 ASTM 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 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 ASTM E 2357.
Air barrier assemblies – combination 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 ASTM E 2357.
Air barrier system – combination 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 and 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.
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
(O2) and nitrogen
.
Building envelope
The building envelope is the physical separator between the interior and the exterior environments of a building. Another emerging term is "Building Enclosure". It serves as the outer shell to help maintain the indoor environment and facilitate its climate control...
. Air barrier products may take several forms:
- Mechanically-attached membranes, also known as housewrapHousewrapHousewrap defines all synthetic replacement materials for sheathing tar paper. These materials are all lighter in weight and usually wider than asphalt designs, so contractors can apply the material much faster to a house shell. Housewrap functions as a weather-resistant barrier, preventing rain...
s, usually a polyethylenePolyethylenePolyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
-fiber or spun-bonded polyolefinPolyolefinA polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
, such as TyvekTyvekTyvek is a brand of flashspun high-density polyethylene fibers, a synthetic material; the name is a registered trademark of DuPont. The material is very strong; it is difficult to tear but can easily be cut with scissors or a knife...
is a generally accepted moisture barrier and an air barrier (ASTM 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 polymeric based and asphaltic based materials
- Closed-cell medium density spray-applied polyurethanePolyurethaneA polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
foam, which typically provides insulation as well - Some open-cell spray-applied polyurethanePolyurethaneA polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
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 material – Building material that is designed and constructed to provide the principal plane of airtightness through the environmental separator 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 ASTM 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 accessory – 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 ASTM 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 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 ASTM E 2357.
Air barrier assemblies – combination 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 ASTM E 2357.
Air barrier system – combination 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 and 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 vaporWater vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...
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
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(O2) and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
.