Building Science of Walls · 3/24/2017 · 2017-03 Rhode Island AIA Presentation 65 Airflow...
Transcript of Building Science of Walls · 3/24/2017 · 2017-03 Rhode Island AIA Presentation 65 Airflow...
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Building Science of Walls
March 24, 2017
Kohta Ueno
2017-03 Rhode Island AIA Presentation 2
Background
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2017-03 Rhode Island AIA Presentation 3
Environmental Separator
2017-03 Rhode Island AIA Presentation 4
What Separation Roles? Water control layer A.k.a. “drainage plane,” “water resistive barrier,”
“weather resistive barrier,” WRB
Housewraps, tar paper… more modern options
Air control layer A.k.a. “air barrier”
Drywall, sheathing, spray foam… and continuity
Vapor control layer A.k.a. “vapor barrier”—poly, Kraft paper, latex paint
Thermal control layer Insulation (fluffy in stud bays, continuous on outside)
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2017-03 Rhode Island AIA Presentation 5
Climate Zone Map (BSC)
2017-03 Rhode Island AIA Presentation 6
Climate Zone Map (DOE)
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2017-03 Rhode Island AIA Presentation 7
Water Control Layer
2017-03 Rhode Island AIA Presentation 8
Housewrap (Residential)
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2017-03 Rhode Island AIA Presentation 9
Housewrap (Commercial)
2017-03 Rhode Island AIA Presentation 10
Billowing Housewrap
Is it really an air barrier (network airflow)?
Potential damage from cyclic loading
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2017-03 Rhode Island AIA Presentation 11
Vapor-Impermeable Adhered Membrane
Cold climate + no exterior insulation = danger
2017-03 Rhode Island AIA Presentation 12
Vapor-Permeable Adhered Membrane
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2017-03 Rhode Island AIA Presentation 13
Self-Adhered Membranes
Self-sealing
Air leakage improvement; no blow-off/billowing
No ‘hidden path’ water leakage/bypass
Reverse laps not as critical
2017-03 Rhode Island AIA Presentation 14
Taped Sheathings (WRB Surface)
Fast dry-in
Airtightness
Reliance on adhesive vs. laps? Surface prep
Rigid foam insulation too
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2017-03 Rhode Island AIA Presentation 15
Taped Joints (Foam Sheathing)
Membrane-type flashing tape at joints
Horizontals more important than verticals
2017-03 Rhode Island AIA Presentation 16
Fluid-Applied WRBs
“Housewrap in a can” (GBA Column)
Continuous water control
Airtightness
Can be applied with air gun (paint sub)
Issues: surface prep, application temperature, substrate condition, etc.
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2017-03 Rhode Island AIA Presentation 17
2017-03 Rhode Island AIA Presentation 18
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2017-03 Rhode Island AIA Presentation 19
2017-03 Rhode Island AIA Presentation 20
Reverse Lap Termination
“Termination mastic” at reverse lap condition
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2017-03 Rhode Island AIA Presentation 21
Water Control‐Hydrostatic Pressure
2017-03 Rhode Island AIA Presentation 22
Water Control and Drainage Gaps
Water control layer
Key is control of hydrostatic pressure
All about “the gap”
See “Mind the Gap” and “Hockey Pucks and Hydrostatic Pressure”
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2017-03 Rhode Island AIA Presentation 23
Hydrostatic Pressure
2017-03 Rhode Island AIA Presentation 24
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2017-03 Rhode Island AIA Presentation 25
2017-03 Rhode Island AIA Presentation 26
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2017-03 Rhode Island AIA Presentation 27
2017-03 Rhode Island AIA Presentation 28
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2017-03 Rhode Island AIA Presentation 29
2017-03 Rhode Island AIA Presentation 30
Wind Speed vs. Pressures
½” of “perched” water ≈ 35 mph wind force
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2017-03 Rhode Island AIA Presentation 31
Water Control Layers and Spaces
2017-03 Rhode Island AIA Presentation 32
Strapped Cavities/“Rainscreen Wall”
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2017-03 Rhode Island AIA Presentation 33
Why Rainscreen/Air Gap
“Sandwiched” water (surface tension) hangs up
Staying wet or wet/dry cycling Paint blow off
Damage over time
2017-03 Rhode Island AIA Presentation 34
Cladding Ventilation
Airflow behind cladding dries out both cladding & backup wall
Brick veneer example
Why vinyl siding and metal panel cladding work in cold climates
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2017-03 Rhode Island AIA Presentation 35
Drainage from Lap Sidings
Added water between siding & housewrap
Lap sidings “self draining”
Window head flashings!
2017-03 Rhode Island AIA Presentation 36
Shingle Wall Rainscreen/Air Gap
Mesh style (Home Slicker, Keene Building Products)
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2017-03 Rhode Island AIA Presentation 37
2017-03 Rhode Island AIA Presentation 38
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2017-03 Rhode Island AIA Presentation 39
2017-03 Rhode Island AIA Presentation 40
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2017-03 Rhode Island AIA Presentation 41
2017-03 Rhode Island AIA Presentation 42
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2017-03 Rhode Island AIA Presentation 43
Windows Flashings
Building Science 2008Windows and Curtainwalls No. 4480
EIFS & Windows ‐
Oops
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2017-03 Rhode Island AIA Presentation 45
Sill Pan Flashings
2017-03 Rhode Island AIA Presentation 46
Backdams and Sloped Sills
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Building Science 2008Windows and Curtainwalls No. 4780
Formable Sub-sill Flashing
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Subsill
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2017-03 Rhode Island AIA Presentation 49
Housewrap Installation Sequence
2017-03 Rhode Island AIA Presentation 50
Housewrap Installation Sequence
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2017-03 Rhode Island AIA Presentation 51
Foam Sheathing Window Flashing
2017-03 Rhode Island AIA Presentation 52
Window Failure Examples
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2017-03 Rhode Island AIA Presentation 53
Window Failure Examples
2017-03 Rhode Island AIA Presentation 54
Window Failure Repair
Stripped shingles and housewrap
Windows pulled, re-flashed (fluid-applied window ‘wrap’), and reinstalled
Fluid-applied WRB
Added rainscreen mat under shingles
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2017-03 Rhode Island AIA Presentation 55
Stucco & Adhered Stone
2017-03 Rhode Island AIA Presentation 56
Stucco on Wood Frame Walls
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2017-03 Rhode Island AIA Presentation 57
Stucco Failures (MN, PA)
2017-03 Rhode Island AIA Presentation 58
Stucco-to-Paper Bond
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2017-03 Rhode Island AIA Presentation 59
2017-03 Rhode Island AIA Presentation 60
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2017-03 Rhode Island AIA Presentation 61
2017-03 Rhode Island AIA Presentation 62
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2017-03 Rhode Island AIA Presentation 63
Adhered Stone Veneer
2017-03 Rhode Island AIA Presentation 64
Air Flow
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2017-03 Rhode Island AIA Presentation 65
Airflow Control: Why
Moisture control air leakage condensation
Comfort and Health Drafts Odors, particles, gases
Energy Heat transferred with air
Sound Required by some codes
If you can’t enclose air, you can’t condition it
2017-03 Rhode Island AIA Presentation 66
Driving Forces
1. Wind Pressures
2. Buoyancy (or stack effect)
3. HVAC
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2017-03 Rhode Island AIA Presentation 67
Driving Forces
Wind Effect Stack Effect Combustion and Ventilation
2017-03 Rhode Island AIA Presentation 68
Wind Flow Patterns
Wind speedincreases
withheight
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2017-03 Rhode Island AIA Presentation 69
2. Stack Effect: Cold Weather
Hot air rises
Tall Building in Winter = Heavy Balloon
+
2017-03 Rhode Island AIA Presentation 70
Stack Effect: Cold Weather “Perfect” Building equally leaky everywhere
Neutral Pressure Plane at mid-height
+
NPP
Air flows in at bottom
Air flows out at top
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2017-03 Rhode Island AIA Presentation 71
Stack Effect: Warm Weather “Perfect” Building equally leaky everywhere
Neutral Pressure Plane at mid-height
+
NPP
Air flows out at bottom
Air flows in at top
2017-03 Rhode Island AIA Presentation 72
Air Barriers
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2017-03 Rhode Island AIA Presentation 73
Air Barrier Systems
Function: to stop airflow through enclosure
ABS can be placed anywhere in the enclosure
Must be strong enough to take wind gusts (code requirement)
Many materials are air impermeable, but most systems are not airtight
2017-03 Rhode Island AIA Presentation 74
Air Barrier Systems: Requirements
Continuous primary need, common failure
Strong designed for full wind load
Durable critical component - repair, replacement
Stiff control billowing, pumping
Air Impermeable (may be vapour permeable)
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2017-03 Rhode Island AIA Presentation 75
“Trace the line”
Poly can be (?) an air and vapour barrierButBEWARE when Air ConditioningDefinitely not in South
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Use drywall, framing members• Seal with sealant, gaskets, etc.•Is stiff, strong•Often easier to ensure quality•Widely applicable to all forms of commercial, residential•Allows choice of vapor permeance
The Airtight Drywall Approach
Air sealing around components: e.g., windows and wallsotherOpenings and penetrations
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Typical Air Leakage Points
Partition-Ceiling
Partition-Wall
Bathtub
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2017-03 Rhode Island AIA Presentation 81
Big holes
Problem:Filter
Solution: Seal
If you can see daylight it is not sealed
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2017-03 Rhode Island AIA Presentation 83
Spray Foam as an Air Barrier
Spray foam doesn’t air seal where it isn’t there!
Wood-to-wood connections
2017-03 Rhode Island AIA Presentation 84
Spray Foam as an Air Barrier
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2017-03 Rhode Island AIA Presentation 85
Spray Foam as an Air Barrier
2017-03 Rhode Island AIA Presentation 86
Cold Weather Condensation in Walls
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2017-03 Rhode Island AIA Presentation 87
Vapor Diffusion vs. Air Leakage
Vapor Diffusion more to less vapor
no air flow
flow through tiny pores
Air Convection more to less air pressure
flow through visible cracks and holes
vapor is just along for the ride
2017-03 Rhode Island AIA Presentation 88
Wall w/o Insulated SheathingAir leakage
Vapor Diffusion
Cold = Condensation
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2017-03 Rhode Island AIA Presentation 89
Frosting on Sheathing
2017-03 Rhode Island AIA Presentation 90
Wall with Insulated SheathingAir leakage
Vapor Diffusion
Warm = no condensation
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2017-03 Rhode Island AIA Presentation 91
Vapor Barriers and the Code
Class I: 0.1 perm or less (polyethylene)
Class II: 0.1 < perm ≤ 1.0 perm (Kraft facing, vapor retarder paint)
Class III: 1.0 < perm ≤ 10 perm(Latex paint)
Polyethylene = no inward drying
More open vapor control allows greater drying—more “forgiveness” in wall
2017-03 Rhode Island AIA Presentation 92
Vapor Barriers and the Code
Can just use latex paint (no vapor barrier) if you add enough insulation outside of the stud bay insulation. Safer -> controls diffusion and air leakage moisture. Zone 5A = 30%/70% R-value ratio
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2017-03 Rhode Island AIA Presentation 93
Thermal Bridging at Framing
2017-03 Rhode Island AIA Presentation 94
Thermal Bridging at Steel Framing
Steel is 400 times more conductive than wood
Steel studs are about 40 times thinner
R=4+
Cold Hot
R<0.3
A 2x6 steel stud wall 16” OC with R-19 Fiberglass Batt = effective R-9 wall assembly.
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2017-03 Rhode Island AIA Presentation 95
Thermal Bridging at Steel Framing
2017-03 Rhode Island AIA Presentation 96
Thermal Bridging at Steel Framing
Summertime/AC example
Sun is hitting the wall (southeast orientation)
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2017-03 Rhode Island AIA Presentation 97
Exterior Continuous Insulation
2017-03 Rhode Island AIA Presentation 98
Exterior Rigid Foam (Taped Seams)
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2017-03 Rhode Island AIA Presentation 99
4” Polyisocyanurate Foam Retrofit
2017-03 Rhode Island AIA Presentation 100
Mineral Fiber, Nailbase Panel
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2017-03 Rhode Island AIA Presentation 101
4” Polyisocyanurate Foam
2017-03 Rhode Island AIA Presentation 102
Foam Sheathing Cladding Attachment
250 lbs/113 kg load (7.8 psf): <0.003” deflection
Wood siding ~2 psfFiber cement 2-3 psfStucco 8-10 psf Image c/o Petersen Engineering
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2017-03 Rhode Island AIA Presentation 103
Foam Sheathing Cladding Attachment
2017-03 Rhode Island AIA Presentation 104
BSC Cladding Attachment Research
System Mechanics
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2017-03 Rhode Island AIA Presentation 105
Full System Laboratory Tests
Looked at initial response full system capacity as well as long term sustained loading
Used full scale samples to limit variations in fastener installation
2017-03 Rhode Island AIA Presentation 106
Recommendations
Based on the results of the testing it is currently recommended to use a maximum load per fastener of no more than 10lbs for up to 4” of insulation
Cladding weight (psf)
16” oc Furring 24” oc Furring
5 18 12
10 9 6
15 6 4
20 4 3
25 3 2
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2017-03 Rhode Island AIA Presentation 107
The “Perfect Wall”
2017-03 Rhode Island AIA Presentation 108
1. Air / Rain Barrier
2. Structural Support
3. Rain Shedding
4. Insulation
Design Info from the 1960’s (Canada)
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2017-03 Rhode Island AIA Presentation 109
The Perfect Wall
2017-03 Rhode Island AIA Presentation 110
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2017-03 Rhode Island AIA Presentation 111
2017-03 Rhode Island AIA Presentation 112
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2017-03 Rhode Island AIA Presentation 113
2017-03 Rhode Island AIA Presentation 114
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2017-03 Rhode Island AIA Presentation 115
2017-03 Rhode Island AIA Presentation 116
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2017-03 Rhode Island AIA Presentation 117
2017-03 Rhode Island AIA Presentation 118
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2017-03 Rhode Island AIA Presentation 119
2017-03 Rhode Island AIA Presentation 120
Window
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2017-03 Rhode Island AIA Presentation 121
The “Perfect” Wall: Higher Performance
2017-03 Rhode Island AIA Presentation 122
The Commercial Steel Frame Wall
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2017-03 Rhode Island AIA Presentation 123
“Perfect Wall” Advantages
Very robust enclosure—“500 year building” Structural portion in “interior” conditions
Institutional/long term buildings
No risk of interstitial condensation
Continuity of control layers Continuous thermal insulation outside
Inspectable and simple air barrier “wrap”
Water control layer/WRB inspectable before insulation
Any interior condition
Any exterior condition
2017-03 Rhode Island AIA Presentation 124
Building the “Perfect Wall”
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2017-03 Rhode Island AIA Presentation 125
Self-adhered membrane, XPS insulation
2017-03 Rhode Island AIA Presentation 126
Fluid-Applied Asphalt & Rock Wool
Asphalt Drainage Plane Air Barrier
Rock wool Insulation
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2017-03 Rhode Island AIA Presentation 127
Exterior Closed Cell Spray FoamAll Four Control LayersSpray foam= air barrier & drainage plane & insulation & vapor control
Transitions, Continuity, Penetrations
2017-03 Rhode Island AIA Presentation 128
Cladding Support (Z-Furring)
Z-furring 16” o.c.,
All this effort to cover up our thermal bridges with insulation… and then we punch steel through it…
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2017-03 Rhode Island AIA Presentation 129
Thermal Bridging at Cladding Thermal Performance of Building Envelope Details for Mid- and High-
Rise Buildings (ASHRAE 1365-RP)
2017-03 Rhode Island AIA Presentation 130
Thermally Broken Cladding Supports
Cascadia Clip (pultruded fiberglass) Knight Wall (fasteners through foam)Engineered Assemblies T Clip
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2017-03 Rhode Island AIA Presentation 131
Questions?Kohta Uenokohta (at sign) buildingscience dot com
This presentation will be available at http://buildingscience.com/past-events
2017-03 Rhode Island AIA Presentation 132
Document Resources Building Science Digest 014: Air Flow Control in Buildings
http://www.buildingscience.com/documents/digests/bsd-014-air-flow-control-in-buildings
Building Science Digest 163: Controlling Cold-Weather Condensation Using Insulationhttps://buildingscience.com/documents/digests/bsd-controlling-cold-weather-condensation-using-insulation
Building Science Insight 001: The Perfect Wall http://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall/
Building Science Insight 005: A Bridge Too Farhttp://www.buildingscience.com/documents/insights/bsi-005-a-bridge-too-far/
Building Science Insight 029: Stucco Woes—The Perfect Stormhttp://buildingscience.com/documents/insights/bsi-029-stucco-woes-the-perfect-storm
Building Science Insight 038: Mind the Gap, Eh!http://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh/
Building Science Insight 048: Exterior Spray Foamhttp://www.buildingscience.com/documents/insights/bsi-048-exterior-spray-foam/
Building Science Insight 057: Hockey Pucks and Hydrostatic Pressurehttp://buildingscience.com/documents/insights/bsi-057-hockey-pucks-and-hydrostatic-pressure
Building Science Insight 062: Thermal Bridges Reduxhttp://www.buildingscience.com/documents/insights/bsi062-thermal-bridges-redux