WALTER SCARBOROUGH CSI CCS CCCA SCIP AIA D+D Specifiers Series Sponsored by Air Barriers

To provide a “big picture” overview of air barriers Webinar Intentions

The Debate is Over Airtightness is essential to high performance building enclosures …

… and air barriers fulfill this critical function The Debate is Over

Genesis of discovery in study of vapor barriers Canadians have led the way in research about vapor barriers because of severe winters Discovery of Air Barriers

Vapor diffusion through materials was less than infiltration of moisture-laden air through openings in the building enclosure Discovery of Air Barriers

Under controlled conditions, 4’ by 8’ sheet of gypsum board Vapor diffusion through board yields 1/3 quart of water Moisture-laden air through 1” square hole yields 30 quarts of water Classic Experiment

“a system of building assemblies within the building enclosure - designed, installed, and integrated in such a manner as to stop the uncontrolled flow of air into and out of the building enclosure.” Air Barrier Defined

Air barriers can also function as a barrier to liquid water infiltration, while allowing water vapor diffusion An Additional Function

Thermal imaging of air infiltration at base Lack of Air Barriers

Thermal imaging of air infiltration around door frame Lack of Air Barriers

Thermal imaging of air infiltration at base and around electrical outlet Lack of Air Barriers

Thermal imaging of air infiltration at window and building corner Lack of Air Barriers

Air barriers have been voluntarily used and included as part of a prudent design however That is about to change Voluntary to Mandatory

2012 International Energy Conservation Code will contain requirements for air barriers Must pass one of three levels of performance: Material Assembly Building Rapidly Approaching Future

Air permeance of less than or equal to cfm/ft 2 under a pressure differential of 0.3 in. w.g. when tested according to ASTM E 2178 Material Performance

Average air leakage rate of less than or equal to 0.04 cfm/ft 2 under a pressure differential of 0.3 in. w.g. when tested according to ASTM E 2357, E 1677, or E 283 Assembly Performance

Air leakage rate does not exceed 0.40 cfm/ft 2 under a pressure differential of 0.3 in. w.g. when tested according to ASTM E 779 Building Performance

Air always flows from: High pressure low pressure Warmer colder Causes of Air Movement

Stack pressure occurs when atmospheric pressure differences exist between the top and bottom of a building Winter Condition Causes of Air Movement

HVAC equipment can create pressure in the building Causes of Air Movement

Winds cause pressure differentials between the interior and exterior Causes of Air Movement

Exterior wall surfaces should shed water Successful Building Enclosure

Inevitably, some uncontrolled moisture- laden air will get past the primary building cladding, then what? Successful Building Enclosure

There should be a barrier that does not allow liquid water to penetrate Successful Building Enclosure

Depending on the geographic location of the building, a barrier that controls the passage of water vapor may be required Successful Building Enclosure

There should be a barrier that prevents the passage of uncontrolled moisture- laden air from penetrating into the building Successful Building Enclosure

There should be a thermal barrier within the building enclosure that retards the movement of heat through the building enclosure Successful Building Enclosure

While water is essential to sustaining life, it is the primary enemy of the building enclosure Successful Building Enclosure

Liquid-applied Exterior side of the wall Different chemical formulas Rolled on or sprayed on Can be applied to almost any surface Forms continuous, seamless membrane Types of Air Barriers

Sheet-applied Exterior side of the wall Different sheet compositions Mechanically attached Seams are taped Forms continuous membrane Types of Air Barriers

Sprayed foam Interior side of the wall Closed cell type Seals joints, gaps, and small openings Types of Air Barriers

There are a considerable number of opportunities for joints, cracks, gaps, and openings Cracks and Openings

Examples of cracks and openings: Joints between differing materials Sealants with bond line failures Joints between rough openings and windows Cracks and Openings

Examples of cracks and openings: Cracks in masonry Joints between sheathing panels Joints around penetrations through the building enclosure Cracks and Openings

Must allow water vapor to pass through the material Attributes of Air Barrier

Must be continuous and free of holes Attributes of Air Barrier

Must be durable during construction Attributes of Air Barrier

Must be resistant to liquid water infiltration to prevent mold Attributes of Air Barrier

Must be resistant to air infiltration to eliminate those cold winter drafts Attributes of Air Barrier

Must be resistant to ultraviolet light degradation because it may be exposed for several months Attributes of Air Barrier

Must be durable over the service life of the building Attributes of Air Barrier

Liquid-applied air barriers must have the ability to bridge cracks in concrete masonry Attributes of Air Barrier

Generally the air barrier is located on the outside face of the sheathing or concrete masonry Location of Air Barriers

Common Myth: “Vapor barrier on warm side in winter” Myth Clarified: Generally applies to northern climates; vapor barriers usually not required in southern climates Air barriers should be used everywhere Location of Air Barriers

Every building, large or small, needs an AIR BARRIER Final Word

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D+D Specifiers Series Sponsored by Questions WALTER SCARBOROUGH CSI CCS CCCA SCIP AIA