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10/9/2012
1
High Performance
Wood Framed Wall Systems
for Passive House Design
Stanley D. Gatland II
CertainTeed Corporation
7777thththth Annual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceSeptember 27September 27September 27September 27----30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO
Session Learning Objectives:
• Understand low-energy building design goals
• Understand how to assess moisture risk in low-
energy wall designs
• Review the four moisture flow mechanisms
• Identify the critical components in constructing
low-energy walls
• Understand the concept of hygrothermal analysis
7777thththth Annual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceAnnual North American Passive House ConferenceSeptember 27September 27September 27September 27----30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO30, 2012 Denver CO
10/9/2012
2
• Low-energy building design goals
• Moisture risk analysis
• Moisture flow mechanisms and common building material hygrothermal properties
• Survey of PHIUS wall assembly details
• Hygrothermal analysis examples
• Q & A Ag
en
da
Ag
en
da
Low-Energy Building Design Goals
Control heat transfer & air leakage :• Increase thermal insulation levels & reduce
thermal bridging• Integrate continuous air barrier systems & space
compartmentalization• Specify high performance fenestration systems
Improve indoor environmental quality (IEQ):• Specify high performance HVAC systems that
include insulated & air tight ductwork• Require controlled & pre-conditioned fresh
air ventilation• Integrate materials that improve indoor air quality
(low emitting, VOC capturing, moisture & mold resistance, etc…)
Reduce solar loads, energy dependence and electricity use:• Integrate passive solar design techniques and
technologies• Improve visual comfort through by increasing
natural light• Specify renewable energy resources• Require energy efficient equipment, appliances
and lighting
Control Heat and Air flow
Space improvements
Energy reduction
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3
Traditional Residential Wall Assembly
• Cladding type
• Water resistive barrier
• Air barrier
• Exterior sheathing
• Frame type
• Cavity insulation
• Interior vapor retarder
• Interior gypsum board
• Interior finish
Climate
Insulation
Air Tightness
Vapor Control
Cladding Design
Cladding
Substrate
Less Risk
Dry
Less
Less
Dynamic
Drain & Vent
Non-Absorptive
Non-Absorptive
More Risk
Wet
More
More
Restrictive
Face Sealed
Absorptive
Absorptive
Moisture Balance Risk Analysis
for Low-Energy Wall Designs
Original concept presented by Mark Williamswith Williams Building Diagnostics, Ltd
10/9/2012
4
Continental US Climate Zone Descriptionswith 2012 IECC Climate Zone Designations
Marine 4C
Pacific NW
Marine 4C
Pacific NW
Cold & Dry
5B, 6B
Cold & Dry
5B, 6B
Mixed & Humid
3A, 4A
Mixed & Humid
3A, 4A
Hot & Humid 1A, 2A, 3AHot & Humid 1A, 2A, 3A
Cold & Humid
5A, 6A
Cold & Humid
5A, 6A
Extreme
Cold & Humid 7A
Extreme
Cold & Humid 7A
Mixed & Dry
3B, 4B
Mixed & Dry
3B, 4B
Hot & Dry 2B, 3BHot & Dry 2B, 3B
Original concept was developed through funding by the US Dept. of Energy’s Building America Program
Cold & Dry
5B, 6B
Cold & Dry
5B, 6B
Extreme
Cold & Humid 7A
Extreme
Cold & Humid 7A
Exterior Interior
GravityGravity
Gravity Flow Protection
• Gravity moves rainwater down
the exterior surfaces of buildings
and water enters through
sloped openings
• Use shingles and flashings to
protect buildings
• Overlap joints in shingle fashion
• Avoid reversed laps
• Use drainage holes along
horizontal and sloped surfaces
• Protect vertical joints with
sealants, gaskets, covers, etc.
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5
Block & Manage Rainwater
• Cladding’s primary purpose is to block rainwater
• Use water resistive barriers (WRBs) as drainage planes behind exterior claddings
• Provide a drainage space between claddings & WRBs
• Ventilated air spaces increase drying potential of wall assembly
• Weep holes required to allow water to drain away from system
Water FilmWater Film
Capillary suction, caused by water
surface tension, draws water into
porous material and tiny cracks
Create capillary breaks to
protect building materials from
absorbing moisture
CavityCavity
Water FilmWater Film
Break Capillary Flow of Moisture
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6
Wall System Type Defines
Moisture Control Strategy
Sorption Isotherms of Wall MaterialsSorption Isotherms of Wall Materials
Mo
istu
re C
on
ten
t %
0
10
15
25
30
0 20 40 60 80 100
Relative Humidity %
20
5
Glass Mat Gypsum Substrate
Gypsum Sheathing Board
Exterior Cement Board
Recycled Paper Board
Oriented Strand Board
Source: Oak Ridge National Laboratory (Wilkes)
Moisture Storage Propertiesof Common Exterior Building Materials
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7
30 Quarts30 Quarts
100X More Moisture by Air Transport than by Diffusion100X More Moisture by Air Transport than by Diffusion
Vapor DiffusionVapor Diffusion
4 x 8 Sheet ofGypsum Board
1/3 Quart1/3 Quart
Air Transport Air Transport
1 in2 Hole
Moisture is Largest Indoor Air Contaminant!
All joints, seams and penetrations
Site-built windows, doors and skylights
Openings between windows and doors
Utility penetrations
Dropped ceilings or chases
Knee walls
Walls and ceilings separating a garage from conditioned spaces
Behind tubs and showers on exterior walls
Common walls between dwelling units
Attic access openings
Rim joist junction
Other sources of infiltration
Specific requirements for fireplaces, fenestrations & recessed lighting
2012 IECC Air Sealing Requirements
10/9/2012
8
Water vapor will move from areas of high vapor pressure to areas of low vapor pressure through building materials
Water Vapor Diffusion
• Test method for determining the
water vapor permeance of
building materials
• Building codes evaluate materials
using the standard dry cup
method, aka Method A or the
Desiccant Method
• Some exterior building materials
are evaluated using the standard
wet cup method, aka Method B or
the Water Method
ASTM E 96 Water Vapor Diffusion Testing
10/9/2012
9
Mean Relative Humidity (%)
Wate
r vap
or
Perm
ean
ce
(Perm
s)
0
10
20
30
40
0 20 40 60 80 100
50
60
Glass Mat Gypsum Substrate
Gypsum Sheathing Board
Exterior Cement Board
Recycled Paper Board
Oriented Strand Board
15 # Felt
Brick, 5/8”
70
80
Source: Oak Ridge National Laboratory (Wilkes)
Water Vapor Permeance
of Common Exterior Wall Materials
Water Vapor Permeanceof Common Interior Wall Materials
0.01
0.1
1
10
100
0 10 20 30 40 50 60 70 80 90 100
Mean Relative Humidity (%)
Wate
r V
ap
or
Perm
ean
ce (
perm
)
Plain Gypsum Board
Primed Gypsum Board
Painted Gypsum Board
2 mil Nylon Film
Asphalt Coated Kraft Paper
6 mil Polyethylene Film
10/9/2012
10
Vapor Retarder Categories
PermPerm
Latex Primed and Painted Gyp. Bd. – 1 & 2 Coats (3 - 35)
Latex Primed Gypsum Board - 1 Coat (22 - 66)
Plain Gypsum Board (45 - 85)
6 mil Polyethylene (0.05 - 0.06)
Asphalt Coated Kraft Paper (0.3 - 3)
2 mil polyamide film (0.8 - 36)
11
Vapor Retarder
(Class II)
Vapor Retarder
(Class II)
Vapor Barrier
(Class I )
Vapor Barrier
(Class I )
0.10.10.010.01 1010
Semi-permeable
(Class III)
Semi-permeable
(Class III) PermeablePermeable100100PermPerm
Latex Primed and Painted Gyp. Bd. – 1 & 2 Coats (3 - 35)
Latex Primed Gypsum Board - 1 Coat (22 - 66)
Plain Gypsum Board (45 - 85)
6 mil Polyethylene (0.05 - 0.06)
Asphalt Coated Kraft Paper (0.3 - 3)
2 mil polyamide film (0.8 - 36)
11
Vapor Retarder
(Class II)
Vapor Retarder
(Class II)
Vapor Barrier
(Class I )
Vapor Barrier
(Class I )
0.10.10.010.01 1010
Semi-permeable
(Class III)
Semi-permeable
(Class III) PermeablePermeable100100
Traditionally vapor retarders are defined by building codes as having a standard dry cup water vapor permeance of 1 perm or less
Vapor Retarder Requirements
• Vapor retarder should be placed at the interior
• Avoid low permeance vapor retarders, such as polyethylene film or aluminum foil in:– Climates with high summer
moisture loads– Walls with moisture storage
claddings– Walls with low permeability
exterior sheathings
• IECC requires Class I or II vapor retarder in Climate Zones 4C, 5, 6, 7 and 8
• SVR works in all North American climate zones
10/9/2012
11
Survey of Certified 30+ PHIUS Projects
Wall Assembly Details
Low-Energy Wall Design Strategies
• Framing
• Interior & exterior sheathing
• Insulation
• Bulk water, air and water vapor flow resistance
• Cladding type & attachment methods
10/9/2012
12
Wood Framing Design Strategies
• Single stud
• 2 x 6 to 2 x 8 stud
• 12” to 16” TJI joists
• Double stud
• 2 x 4 plus 2 x 6
• 2 x 4 plus 12” to 14” TJI joist
• Standard stud framing thermally improved with 2” to 6” insulation board
Photograph courtesy of Katrin Klingenberg
Interior & Exterior Sheathing Design Strategies
• Exterior
• Fiberboard
• OSB
• Interior
• Gypsum
• OSB
• Structural Insulation Panels (SIPS)
Photograph courtesy of Katrin Klingenberg
10/9/2012
13
Insulation Design Strategies
• High density fiberglass batts
• Blown in blanket systems using loose fiberglass
• Dense packed dry cellulose with exterior insulation
• Hybrid insulation systems that include 2” closed cell spray polyurethane foam at the exterior sheathing
• 2” to 6” thick exterior insulation board (PISO or XPS)
Photograph courtesy of Katrin Klingenberg
Water and Air Flow ResistanceDesign Strategies
• Water resistive barriers• House wraps
• Multi-functional OSB sheathing boards
• Multi-functional coatings
• Air barrier systems• Sealed sheathings
• Interior films
• Multifunctional coatings
• Detail is critical at:• Penetrations & seams
• Large rough openings
• Material transitions
• Framing intersections
Sealed Building Wrap
Sealed Smart Vapor Retarder
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14
Cladding Design Strategies
Material typeAbsorptive
Non-absorptive
Attachment methodsDrainage
Ventilation
Photograph courtesy of K. Klingenberg
Hygrothermal Analysis Examples
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15
• Hygrothermal analysis predicts the impact of transient heat and moisture transfer on building envelopes over time
• Used on planned construction projects and existing buildings with moisture problems
• Specialized software helps the user visualize:– Surface condensation and mold growth potential
– Wetting and drying potential of the building envelope
– Moisture content of building components
• Helps building designers evaluate potential pre-construction moisture risks
• Post-construction, helps analyze and solve moisture problems
• ANSI/ASHRAE Standard 160-2009, “Criteria for Moisture-Control Design Analysis in Buildings
Hygrothermal Analysis of Building Envelopes
Passive House Wall Construction
9 ¼” ThickR39
3 ½” thickR13
Fiber Cement Siding1” Air Space
SBPO Building Wrap
½” OSB ½” Gypsum Bd
10/9/2012
16
Cold Climate – Indianapolis, IN
Sheathing Moisture Content Comparison
Exterior Sheathing Moisture Content
0
5
10
15
20
25
10/1/0
0
4/1/
01
10/1/0
1
4/1/
02
10/1/0
2
4/1/
03
10/1/0
3
Date (m/d/y)
Mo
istu
re C
on
ten
t (%
)
Plywood
Wood-Fibre Board
10/9/2012
17
Surface Relative Humidity Comparison
Surface Relative Humidity Comparison
Backside of Exterior Sheathing
0102030405060708090
100
10/1/0
0
2/1/
01
6/1/
01
10/1/0
1
2/1/
02
6/1/
02
10/1/0
2
2/1/
03
6/1/
03
10/1/0
3
Date (m/d/y)
Su
rface R
ela
tive H
um
idit
y (
%)
Plywood
Fiberboard
Passive House Wall Design
Pittsburgh, PA• Cladding
– Fiber cement– Mounted on furring
• Double stud wall with 10” TJI and 2 x 4 studs
• OSB exterior sheathing• Gypsum interior sheathing• 1” XPS or high-density
fiberglass board, air tight stud separator (with and without water vapor control)
• WRB– Spun bonded polyolefin– Air tight install
10/9/2012
18
Passive House Wall Design
% Moisture Content (MC) Comparison
No Interior Vapor Control
Max. MC after 36 months ~23%
With Interior Vapor Control
Max. MC after 36 months ~15%
Passive House Wall Design - Indianapolis, INPaint Only vs. SVR as Vapor Control Layer
• Cladding– Fiber cement
– Mounted on furring
• Single 16” TJI stud
• Sheathing (air tight)
– Fiberboard exterior
– Gypsum interior
• WRB– Spun bonded polyolefin
– Air tight install
10/9/2012
19
Passive House Wall Design
% Moisture Content Comparison
No Interior Vapor Control
Max MC after 36 months ~17%
Smart Vapor Retarder
Max MC after 36 months ~12%
Good Low-Energy Wall Information
• John Straube and Jonathan Smegal, Building America Special Research Project: High-R Walls Case Study Analysis, Research Report – 0903, Building Science Corporation, March 11, 2009 (Rev. June 8, 2011)
• Robb A. Aldrich, Lois Arena and William Zoeller, Practical Residential Wall Systems: R‐30 and Beyond, Building America Research Report, Steven Winter Associates, 2009
10/9/2012
20
Summary & Discussion
• Know the climate & microclimate
• Orientation makes a difference
• Building envelope air tightness is critical
• Successful integration of water resistive and air
barrier systems are critical
• Use cladding ventilation and drainage strategies
to enhance drying to the outside
• Use dynamic vapor control layers with smart,
hygroscopic material properties
• Use hygrothermal analysis to predict and/or
check performance
Question & Answer Session
Thank you for your attention!