Transcript Presentation_Slides

D+D Specifiers
Series
Air
Barriers
WALTER SCARBOROUGH
CSI CCS CCCA SCIP AIA
[email protected]
214.491.7385
Sponsored by
Webinar Intentions
To provide a
“big picture”
overview of air
barriers
The Debate is Over
Airtightness is essential to high
performance building enclosures …
The Debate is Over
… and air barriers fulfill this critical function
Discovery of Air Barriers
• 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
Classic Experiment
• 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
Air Barrier Defined
“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.”
An Additional Function
Air barriers can
also function as a
barrier to liquid
water infiltration,
while allowing
water vapor
diffusion
Lack of Air Barriers
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
Voluntary to Mandatory
Air barriers have been voluntarily used
and included as part of a prudent
design
however
That is about to change
Rapidly Approaching Future
2012 International Energy Conservation
Code will contain requirements for air
barriers
Must pass one of three levels of
performance:
• Material
• Assembly
• Building
Material Performance
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
Assembly 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
Building 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
Causes of Air Movement
Air always flows from:
• High pressure
• Warmer
colder
low pressure
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
Successful Building Enclosure
Exterior wall
surfaces should
shed water
Successful Building Enclosure
Inevitably, some uncontrolled moistureladen 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 moistureladen 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
Types of Air Barriers
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
Cracks and Openings
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
Attributes of Air Barrier
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
Location of Air Barriers
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
Final Word
Every building, large or small, needs an
AIR BARRIER
Most Valuable Resource
D+D Specifiers
Series
Questions
WALTER SCARBOROUGH
CSI CCS CCCA SCIP AIA
[email protected]
214.491.7385
Sponsored by