03 - air barriers and critical details... solutions for the built world air barriers and critical...
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SOLUTIONS FOR THE BUILT WORLD
Air Barriers and Critical Details
Mike Duncan, P.E.
Everett VerSchave, RA
A Consultants Perspective
www.wje.com
SOLUTIONS FOR THE BUILT WORLD
Air Barriers and Critical DetailsA Consultants Perspective
Part II Case Studies
Penetrations
Wall‐to‐Roof Transitions
Glazing System Transitions
Part I Exterior Wall Assemblies
Functional Control Layers Air Barrier Types Making Educated Decisions
Water Barrier (Water‐Resistive Barrier ‐WRB) Prevents (mostly) the passage of liquid water
Air Barrier Prevents (mostly) the passage of air
Prevents the transport of heat/cold via air migration
Prevents the transport of moisture vapor via air migration
Thermal Control Layer (Insulation) Limits the transfer of heat/cold via conduction
Vapor Control Layer (Vapor Retarder/Vapor Barrier) Limits the transfer of vapor via diffusion
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4 Functional Control Layers:
Helps prevent condensation problems
Increases energy efficiency and decreases load on mechanical systems
Increases occupant comfort
In general, makes the building more durable and sustainable
In the 2012 IECC, air barriers are now a code requirement:
“C402.4.1 Air Barriers. A continuous air barrier shall be provided throughout the building
thermal envelope. The air barriers shall be permitted to be located on the inside or
outside of the building envelope, located within the assemblies composing the envelope,
or any combination thereof. . .”
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Why have air barriers become important?
Water Barrier (Water‐Resistive Barrier ‐WRB) Prevents (mostly) the passage of liquid water
Air Barrier Prevents (mostly) the passage of air
Prevents the transport of heat/cold via air migration
Prevents the transport of moisture vapor via air migration
Thermal Control Layer (Insulation) Limits the transfer of heat/cold via conduction
Vapor Control Layer (Vapor Retarder/Vapor Barrier) Limits the transfer of vapor via diffusion
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4 Functional Control Layers:
Water Barrier (Water‐Resistive Barrier ‐WRB) Prevents (mostly) the passage of liquid water
Air Barrier Prevents (mostly) the passage of air
Prevents the transport of heat/cold via air migration
Prevents the transport of moisture vapor via air migration
Thermal Control Layer (Insulation) Limits the transfer of heat/cold via conduction
Vapor Control Layer (Vapor Retarder/Vapor Barrier) Limits the transfer of vapor via diffusion
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4 Functional Control Layers:
Air / Water Barrier
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Functional Control Layers: Three Air / Water Barrier Types
Mechanically‐attached sheets
Self‐adhered sheets
Fluid‐applied
Role of the Exterior Cladding (5th Control Layer) Aesthetics
Protect the air / water barrier
Weather‐shedding (rain, wind, and UV)
Prevents physical damage (once in place)
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Mechanically‐Attached Sheets
Strengths: Inexpensive
Plenty of products available, but . . .
only 2 certified through the ABAA
Not affected by installation
temperature
(example: Tyvek Commercial Wrap)
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Weaknesses Air barrier installation requirements
More readily damaged during
construction
Poor sealing at fasteners
Simple shingle‐lap is no longer good
enough
Mechanically‐Attached Sheets(example: Tyvek Commercial Wrap)
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Self‐Adhered Sheets
Strengths: Fully‐adhered to substrate
Workable at changes in plane, but not
great for complex geometries
Less temperature sensitive at time of
installation (≥ 0°F) than fluid‐applied
Similar to installing peel‐and‐stick
flashing, so relatively quick learning
curve
(example: Henry Blueskin VP160)
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Weaknesses: Usually requires a primer
Numerous laps and seams
Entire surface needs to be rolled (not
just applied with hand pressure)
Many are not vapor permeable
Limited selection
Self‐Adhered Sheets(example: Henry Blueskin VP160)
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Fluid‐Applied
Strengths: Fully‐adhered to substrate
Conforms to irregular substrate
conditions
Relatively monolithic – few joints or laps
Most seal at fasteners
Generally considered high performing
(example: Carlisle Barritech VP)
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Weaknesses: More costly ‐ takes more skill and
equipment to install
More temperature sensitive at time of
application (≥ 40°F)
Not all products are created equal
(especially in this category)
Fluid‐Applied(example: Carlisle Barritech VP)
Air Barrier Material ≠ Air Barrier (continuity‐continuity‐continuity) Material / Assembly / System
Think of it as a complete system – roof, walls, windows, etc.
An air barrier is a structural element Must be able to withstand air pressure differentials
With Fluid‐Applied systems Dry mil thickness vs. Wet mil thickness vs. overall mil thickness
Perm ratings are based on a specific thickness of material
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Final AWB Thoughts:
Consider the enclosure as an integrated system Transitions, penetrations, and terminations are critical Compatibility of various materials within the system
Consider performance expectations What are the owner’s and/or end‐user’s expectations What is the intended service life of the building and the cladding
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Making Educated Decisions:
Consider the enclosure as an integrated system Transitions, penetrations, and terminations are critical Compatibility of various materials within the system
Consider performance expectations What are the owner’s and/or end‐user’s expectations What is the intended service life of the building and the cladding
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Making Educated Decisions:
www.wje.com
SOLUTIONS FOR THE BUILT WORLD
Air Barriers and Critical DetailsA Consultants Perspective
Part II Case Studies
Penetrations
Wall‐to‐Roof Transitions
Glazing System Transitions
Part I Exterior Wall Assemblies
Functional Control Layers Air Barrier Types Making Educated Decisions
Air Barrier and Water‐Resistive Barrier Larger Penetrations – Windows/Glazing Systems Smaller Penetrations – HVAC, Conduit, etc.
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Penetrations
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Penetrations
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Penetrations
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Penetrations
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Penetrations
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Penetrations
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Penetrations
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Penetrations
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Penetrations
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Penetrations
Lag Bolts
Air Barrier Anchors
Window Anchors
Stucco Accessory Anchors
Stucco Lath Anchors
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Penetrations
HVAC penetration created BEFORE air barrier was installed.
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Penetrations
Electrical J-box penetration created AFTER air barrier was installed.
Museum, southwest Colorado
Museum – humidified and positively pressurized interior environment: air barrier detailing critical
Complicated building geometries
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Failed Air Barriers
First known problems – 12 months after construction
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Failed Air Barriers ‐Museum
Water staining
Partial collapse of exterior soffit
Visible problems
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Water staining
Partial collapse of exterior soffit
Failed Air Barriers ‐Museum
Partial soffit collapse
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Failed Air Barriers ‐Museum
Wetting of boards resulted in cupping
Partial soffit collapse
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Failed Air Barriers ‐Museum
Cupping resulted in disengagement of clips
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Failed Air Barriers ‐Museum
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Failed Air Barriers ‐Museum
Investigation – exploratory openings
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Failed Air Barriers ‐Museum
Unsealed penetrations in air barrier
Discontinuous air barrier at roof-to-wall
Exterior cladding staining
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Failed Air Barriers ‐Museum
Disassembly at exterior deck Discontinuous air barrier
Additional exploratory
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Failed Air Barriers ‐Museum
Additional air barrier discontinuities
Review of drawings
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Failed Air Barriers ‐Museum
Review of drawings Very complicated design/unique
geometries Designer did not clearly detail air barrier “Continuity” note buried in the
specifications Air barrier transition could not have been
built
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Failed Air Barriers ‐Museum
Repair – performed from the exterior where possible
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Failed Air Barriers ‐Museum
Repair – most repairs performed from the interior
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Failed Air Barriers ‐Museum
Repair – most repairs performed from the interior
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Failed Air Barriers ‐Museum
Sensors installed as part of investigation used to monitor repairs
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Failed Air Barriers ‐Museum
Wireless sensors installed at critical details
Sensors installed as part of investigation used to monitor repairs
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Failed Air Barriers ‐Museum
Repairs installed
Sensors installed as part of investigation
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Failed Air Barriers ‐Museum
Pressure reversal interval
Natatorium, near Albuquerque, New Mexico
Natatorium – highly humidified and warm interior
Tall open space (stack effect) Air barrier detailing critical
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Failed Air Barriers
First known problems – within 2 years following construction
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Failed Air Barriers ‐ Natatorium
Water drippingEfflorescence at base of EIFS wall
Investigation – exploratory openings
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Failed Air Barriers ‐ Natatorium
Investigation – exploratory openings
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Failed Air Barriers ‐ Natatorium
Deteriorated parapet sheathing Condensation in parapet stud cavity
Investigation – exploratory openings
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Failed Air Barriers ‐ Natatorium
Investigation – exploratory openings
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Failed Air Barriers ‐ Natatorium
Investigation – exploratory openings
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Failed Air Barriers ‐ Natatorium
Investigation – exploratory openings
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Failed Air Barriers ‐ Natatorium
Review of drawings
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Failed Air Barriers ‐ Natatorium
Review of drawings
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Failed Air Barriers ‐ Natatorium
Review of drawings
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Failed Air Barriers ‐ Natatorium
Repair
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Failed Air Barriers ‐ Natatorium
Repair
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Failed Air Barriers ‐ Natatorium
Repair
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Failed Air Barriers ‐ Natatorium
Repair
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Failed Air Barriers ‐ Natatorium
Repair
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Failed Air Barriers ‐ Natatorium
Hotel, eastern Wisconsin
Vinyl interior wallpaperMasonry facade
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Failed Air Barriers
First known problems – within 3 years following interior remodel
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Failed Air Barriers – Reservoir Cladding
Biological growth
Corrosion and moisture staining
Investigation – exploratory openings
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Failed Air Barriers – Reservoir Cladding
Investigation – exploratory openings
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Failed Air Barriers – Reservoir Cladding
Exte
rior W
all
Hal
lway
Investigation – exploratory openings
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Failed Air Barriers – Reservoir Cladding
Exte
rior W
all
Hal
lway
Investigation – exploratory openings
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Failed Air Barriers – Reservoir Cladding
Investigation – exploratory openings
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Failed Air Barriers – Reservoir Cladding
Investigation – exploratory openings
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Failed Air Barriers – Reservoir Cladding
Cause of the biological growth Free transport of humidified exterior airWater‐resistive barrier is not air barrier
Rain saturates masonry Sun causes cavity to become humid
and air expands Air moves to the interior through
discontinuities in air/vapor retarder Air condenses on cool surfaces
behind vinyl wallpaper
Solutions for the Built World Page 72
Failed Air Barriers Vapor and Air Retarder
Repairs
Re‐clad not cost effective (second phase if necessary)
Reduce wetting of masonry cladding Provide air/vapor retarder Improve breathability of wall finishes
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Failed Air Barriers – Reservoir Cladding
Repairs
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Failed Air Barriers – Reservoir Cladding
Repairs
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Failed Air Barriers – Reservoir Cladding
Repairs
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Failed Air Barriers – Reservoir Cladding
Repairs
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Failed Air Barriers – Reservoir Cladding
www.wje.com
SOLUTIONS FOR THE BUILT WORLD
Air Barriers and Critical Details
Mike Duncan, P.E.
Everett VerSchave, RA
A Consultants Perspective