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


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

Solutions for the Built World

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. . .”


Why have air barriers become important?









Air / Water Barrier


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)


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)


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)


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)


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)


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)


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


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


Making Educated Decisions:

www.wje.com


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.


Penetrations


Penetrations


Penetrations

Lag Bolts

Air Barrier Anchors

Window Anchors

Stucco Accessory Anchors

Stucco Lath Anchors


Penetrations

HVAC penetration created BEFORE air barrier was installed.


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


Failed Air Barriers

First known problems – 12 months after construction


Failed Air Barriers ‐Museum

Water staining

Partial collapse of exterior soffit

Visible problems


Water staining

Partial collapse of exterior soffit


Partial soffit collapse



Wetting of boards resulted in cupping

Partial soffit collapse



Cupping resulted in disengagement of clips

Investigation – exploratory openings



Unsealed penetrations in air barrier

Discontinuous air barrier at roof-to-wall

Exterior cladding staining



Disassembly at exterior deck Discontinuous air barrier

Additional exploratory



Additional air barrier discontinuities

Review of drawings



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



Repair – performed from the exterior where possible



Repair – most repairs performed from the interior



Sensors installed as part of investigation used to monitor repairs



Wireless sensors installed at critical details

Sensors installed as part of investigation used to monitor repairs



Repairs installed

Sensors installed as part of investigation



Pressure reversal interval

Natatorium, near Albuquerque, New Mexico

Natatorium – highly humidified and warm interior

Tall open space (stack effect) Air barrier detailing critical


Failed Air Barriers

First known problems – within 2 years following construction


Failed Air Barriers ‐ Natatorium

Water drippingEfflorescence at base of EIFS wall




Deteriorated parapet sheathing Condensation in parapet stud cavity

Review of drawings



Repair



Hotel, eastern Wisconsin

Vinyl interior wallpaperMasonry facade


Failed Air Barriers

First known problems – within 3 years following interior remodel


Failed Air Barriers – Reservoir Cladding

Biological growth

Corrosion and moisture staining




Exte

rior W

all

Hal

lway

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


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



Repairs



www.wje.com


Air Barriers and Critical Details

Mike Duncan, P.E.

Everett VerSchave, RA

A Consultants Perspective

03 - air barriers and critical details... solutions for the built world air barriers and critical...

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