exterior systems for wood-framed building envelopes
TRANSCRIPT
Code Compliant Exterior Systems for
Wood-framed Building Envelopes
Presented by Tim Farrell1 LU/HSW
Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or theSoftwood Lumber Board.
Sponsored by Huber Engineered Woods,Makers of
Course Description
This course investigates the most recent code changes
emphasizing building envelope performance. We will explore
next generation integrated solutions that simultaneously provide
protection against moisture penetration, air leakage, and
thermal bridging. Installation benefits and on-site quality control
issues related to multi-solution integrated systems will also be
evaluated.
Course ObjectivesAfter completion of this course, participants will be equipped to:
• Delineate the latest code and design standards for wood
framed exterior wall assemblies.
• Assess different product approaches available to meet air
barrier and water-resistive barrier (WRBs) requirements in the
International Building Code.
• Analyze the differences between multi-product solutions and
single product solutions for wood framed building envelopes.
• Articulate the benefits of continuous insulation added to
exterior sheathing.
Course Outline
Part 1• Moisture
Management
Part 2• Air Leakage
Management
Part 3• Vapor
Management
Part 4• Thermal
Management
Part 5• Alternative
Solutions
Introduction• In a tight building
– Heating and cooling
efficiencies can be
maximized
– Ventilation system
can manage
moisture levels and
indoor air quality
• High performance
rewarded by LEED and
other green building
programs
IntroductionConventional methods:
– Caulk
– Building felt
– House wrap
Replaced by High-performance panels:
– With integrated weather barrier
– Help eliminate the risk of water trapped
between building wrap and sheathing
– Engineered to allow permeability
– Enables the building to dry
SECTION 1Moisture Management
Moisture Management in Buildings Moisture is the single greatest
threat to a building’s
durability and long-term
performance.
• Rot• Mold• Mildew• Corrosion• Maintenance problems• Poor indoor air quality• Building system failure• Liability issues for building
designers and owners
Moisture Management in Buildings
• Liquid water carried into a building
through holes and cracks
• Air leakage carrying water vapor
• Water vapor diffusion
Greatest risk
Moderate risk
Lowest risk
Moisture Management in Buildings
Four key strategies,
known as the Four Ds,
keep moisture from
getting into a building.
The Four D's• Deflection• Drainage• Drying • Durability
Moisture Management in Buildings
The Four Ds have two objectives:
1. Prevent moisture from getting into the
structure in the first place (deflection)
2. Any moisture that does get into the
structure must be managed as quickly
and thoroughly as possible (draining,
drying, and durability)
Definitions
• EXTERIOR WALL COVERING – An assembly of materials applied on the exterior side of exterior walls for the purpose of providing a
weather-resistive barrier.
• WATER-RESISTIVE BARRIER - A material behind an exterior wall
covering that is intended to resist
liquid water that has penetrated
behind the exterior covering
Moisture Management
• Water-resistive barrier - One layer of No. 15 asphalt felt, free from
holes and breaks, complying with ASTM D 226 for Type 1 felt or other
approved water-resistive barrier shall be applied over studs or
sheathing of all exterior walls.
ICC Acceptance Criteria for WRB
Moisture Management
• The exterior wall envelope shall
be constructed in a manner
that prevents the accumulation
of water within the wall
assembly by providing a water-
resistant barrier behind the
exterior veneer and a means of
draining to water that enters
the assembly.
Drainage• Oregon Code – The envelope
shall consist of a water resistive
barrier and a minimum 1/8”
space between WRB and
exterior veneer.
• Exception – A space is not
required when using a WRB
that meets 75% drainage
requirement of ASTM E2273
Moisture Management
• Approved corrosion-resistant flashing shall be applied in a manner
to prevent entry of water into the wall cavity or penetration of
water to the building structural framing components. Self-adhered
membranes used as flashing shall comply with AAMA 711.
SECTION 2Air Leakage Management
Air Leakage
Uncontrolled air flow:
• Introduces moisture that can
cause rot and mold
• Can increase energy use
• Can reduce effectiveness of
insulation
• Can impact indoor air quality
Typical House Wrap
Building Envelope — A System of Many
• No one product can control air leakage
• Air tightness is a function of the entire building envelope
• Everything must work together to achieve effective air tightness
The airtightness of a building envelope cannot be underestimated. A
building’s energy efficiency, occupant comfort and sustainability
depend on it.
Air Leakage
2015 IECC - Air Leakage
Commercial C402.5
• Prescriptive Option or
• Testing Option
Residential R402.4
• Testing Only
2015 IECC - Air Leakage
Commercial Prescriptive Option
• A continuous air barrier shall be provided throughout the building
thermal envelope.
• Air barrier joints and seams shall be sealed to resist positive and
negative pressure from wind, stack effect and mechanical
ventilation.
• The continuous air barrier will comply with…
Air Barrier Material Testing
• ASTM E2178 Air Permeance of Building Materials
• 1.0 m x 1.0 m specimen with no seams or transitions
• Must achieve less than 0.02 L/(s•m2) @ 75 Pa
Air Barrier Assembly Testing• ASTM E2357 Air Leakage of Air
Barrier Assemblies
• 8.0 ft x 8.0 ft wall with penetrations/transistions
• Includes wind cycling
• Measures infiltration and exfiltration
• Must achieve less than 0.2 L/(s•m2) @ 75 Pa
2015 IECC - Air Leakage
Commercial Testing Option
• Blower door testing in
accordance with ASTM E 779 at
a pressure differential of 75 Pa
• Air leakage rate no greater than
0.40 cfm/ft2
• Regardless of Climate Zone
2015 IECC - Air LeakageResidential Air Leakage Testing
• Blower door testing in accordance with
ASTM E 779 at a pressure of differential
of 50 Pa
• Max leakage rate of 5 ACH in Climate
Zones 1and 2,
• Max leakage rate of 3 ACH in Climate
Zones 3 through 8.
• Sill plate shall be sealed at foundation
• Top plate shall be sealed at top of
exterior walls.
• Knee walls shall be sealed.
Residential Air Leakage Compliance MethodsAir Changes per Hour (ACH) at 50 Pascals of pressure (50 Pa)
Climate Zone 2006 IECCVisual inspection
only
2009 IECCVisual inspection or blower door
2012 IECCBlower door only
2015 IECCBlower door only
1 Follow checklist
Follow checklist or 7
ACH
5 ACH 5 ACH
2 Follow checklist
Follow checklist or 7
ACH
5 ACH 5 ACH
3 Follow checklist
Follow checklist or 7
ACH
3 ACH 3 ACH
4 Follow checklist
Follow checklist or 7
ACH
3 ACH 3 ACH
5 Follow checklist
Follow checklist or 7
ACH
3 ACH 3 ACH
6 Follow checklist
Follow checklist or 7
ACH
3 ACH 3 ACH
7 Follow Follow 3 ACH 3 ACH
Air Leakage
Building wraps
• Pros:
– Can help decrease air leaking provided all seams, edges and details
are sealed, and that it is caulked at the bottom
• Cons:
– Sometimes susceptible to ripping or tearing
– Must be handled carefully
Air Leakage
Taped wall sheathing panels
• Form a continuous protective
air barrier
• Reduce air leakage through
walls or roofs
• Lower air changes per hour
• Help optimize R-value
• Save energy
• Meet stringent codes and
certifications
SECTION 3Vapor Management
Vapor Management
• Water as vapor causes problems
when it becomes trapped in an
assembly and turns to liquid
(condensation)
• Water vapor moves by two
mechanisms—air transport and
vapor diffusion
AIR-TRANSPORTED MOISTURE > VAPOR DIFFUSION
Vapor Management
• Warm air holds more
moisture than cold air
• Air leakage can carry
significant amounts of
moisture into the
building enclosure
Air Leakage vs. Vapor Diffusion
In one year, 100 times more moisture is transported by air leakage compared to diffusion…and gypsum is 50 perms!
Solid 4x8 sheet of gypsum
4x8 sheet of gypsum with a 1 in2 hole
Interior at 70° F and 40% RH
Vapor Management
Warm Moist Interior Cold Dry Exterior
The 2015 IBC/IRC provides
methods to prevent
condensation by
controlling temperature
and humidity in primarily
two ways:
Interior Vapor Retarders
Exterior Insulation
Vapor Management
2015 IBC - Vapor
Vapor Permeance
Low
HighClass I or II Vapor
Retarders are required
on the inside of framed
walls in Climate Zones 5-
8 and Marine 4
2015 IBC - Vapor
Vapor Permeance
Low
HighClass III Vapor Retarders shall be permitted when exterior insulation is used
Climate Zone
2x4 2x6
Marine 4 R > 2.5 R > 3.75
5 R > 5 R > 7.5
6 R > 7.5 R > 11.25
7 & 8 R > 10 R > 15
Vapor Management
• DO: Encourage inward drying by using the most vapor permeable
option. Don’t use Class I if Class II is allowed
• DON'T: Install Class I vapor retarders such as polyethylene, foil-faced
batt insulation, or vinyl wall coverings on the interior of air-
conditioned assemblies
• DON'T: Install Class I vapor barriers on both sides of wall assemblies, ie.
thick rigid foam on the outside and poly on the inside.
SECTION 3Thermal Management
2015 IECC - Thermal
Commercial C402.1
• Prescriptive Table
• Assembly U-Factor
Residential R402.1
• Prescriptive Table
• U-Factor Alternative
• Total UA Alternative
ADD IMAGE
Thermal Bridging
Cavity Insulation
Framing
Commercial Wood Framed WallsR-Value Requirements
Climate Zone 2009 IECC 2012 IECC 2015 IECC ASHRAE 90.1-2013
1 13 20 or 13+3.8 20 or 13+3.8 132 13 20 or 13+3.8 20 or 13+3.8 133 13 20 or 13+3.8 20 or 13+3.8 134 13 20 or 13+3.8 20 or 13+3.8 20 or 13+3.8
Marine 4 13+3.8 20 or 13+3.8 20 or 13+3.8 20 or 13+3.8
5 13+3.8 20 or 13+3.8 20 or 13+3.8 19+5 or 13+7.5
6 13+7.5 20+3.8 or 13+7.5
20+3.8 or 13+7.5
19+5 or 13+7.5
7 13+7.5 20+3.8 or 13+7.5
20+3.8 or 13+7.5
19+5 or 13+7.5
8 13+15.6 20+10 or 13+15.6
20+10 or 13+15.6 13+18.8
Single Family Residential Wood Framed Walls R-Value Requirements
Climate Zone
2006 IECC 2009 IECC 2012 IECC 2015 IECC
1 13 13 13 13
2 13 13 13 13
3 13 13 20 or 13+5 20 or 13+5
4 13 13 20 or 13+5 20 or 13+5
5 & Marine 4 20 or 13+5 20 or 13+5 20 or 13+5 20 or 13+5
6 20 or 13+5 20 or 13+5 20+5 or 13+10
20+5 or 13+10
7 & 8 21 21 20+5 or 13+10
20+5 or 13+10
Thermal Definitions
• R-Value: Measure of thermal resistance• U-Factor: Measure of thermal transmittance
R-Value = 1/U-FactorU-Factor = 1/R-Value
Calculation: Area weighted
average U-factor
U = (0.25x0.160) + (0.75x0.067)U = 0.090R = 11.08
Wall Assembly U-Factor and R-Value (2x6 at 16” o.c. wall)
Wall Component
A1 A2
Lap Siding 0.81 0.81
OSB Sheathing
0.62 0.62
Framing or Insulation
4.38 13
Drywall 0.45 0.45
Total R-Value
6.26 18.88
U-Factor 0.160 .067
% of Wall Area
25% 75%
U-Factor ExampleA2
A1
SECTION 5Alternative Solutions
Alternative Solutions
OSB Panel with Integrated Moisture
Barrier
• Structural OSB panel with
integrated moisture barrier
• Continuous water and air barrier
that improves energy efficiency
by significantly reducing air
leakage
• After taping, a lasting
protective barrier has been
established
Alternative SolutionsKey Features and Components of OSB
Panel with Integrated Moisture Barrier
• High quality structural sheathing panel
made of engineered wood
• Built-in vapor permeable water-
resistive barrier eliminates the
complexities of installing of building
wrap and felt
• Engineered for enhanced drainage of
bulk water and optimal permeability
• Allows water vapor to pass through
and promote drying
Alternative Solutions
Key Features and Components of OSB
Panel with Integrated Moisture Barrier
• Continuous, rigid air barrier
• Decreases unwanted air leakage
• Greater energy efficiency
• Seam sealing flashing tape with high-
performance acrylic adhesive bonds
provides permanent protective seal
Alternative Solutions
OSB Panel with Integrated Moisture
Barrier
• Seam sealing acrylic tape can be
used as flashing tape, which
minimizes the chance for flashing
installation errors
• Unlike with many conventional
products, windy weather does
not impede tape application
Conclusion•Building codes drive increased performance requirements for building envelopes.
•Traditional solutions attempt to create an integrated system from individual components.
•Creating a high performance system out of traditional products is challenging.
•Code compliant multi-solution systems install easily and perform reliably, mitigating the risk of envelope failure.
This concludes the Huber
Engineered Woods LLC, AIA/CES
Continuing Education Program
For additional information, visit:
• www.huberarchitectlibrary.com
• For Technical questions:
800-933-9220 ext. 2716 or
This concludes The American Institute of Architects Continuing Education Systems Course
QUESTIONS?
Tim Farrell
Huber Engineered Woods