WALTER SCARBOROUGHCSI CCS CCCA SCIP AIAwscarborough@hbig.us214.491.7385

D+D Specifiers Series

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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 0.004 cfm/ft2 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/ft2 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/ft2 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

Most Valuable Resource

D+D Specifiers Series

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Questions

WALTER SCARBOROUGHCSI CCS CCCA SCIP AIAwscarborough@hbig.us214.491.7385