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Building Science 2013 Environmental Separation
John Straube, Ph.D., P.Eng
presented by www.buildingscience.com
Pre-WWII Buildings
• No added insulation (or very little) • Heating systems and some natural ventilation • No air conditioning • No vapor barriers • Few explicit air-tightening or “draft-stopping” details • Masonry and old-growth solid timber structures • Plaster is the dominant interior finish
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Mold, Rot, Corrosion, Decay, Recladding
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Performance?
• More than on-time, on-budget, to code – Safe – Healthy – Comfortable
• A growing clamor for…. – Durable – Low-energy – Maintainable – Modifiable – Repairable
• All delivered reliably, predictably www.BuildingScience.com
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Why High Performance? Green?
• Changing needs • Rising comfort/amenity expectations • Control energy / maintenance costs
Building Functions
• Human needs… more than shelter (e.g. Location, Shelter, Utility, Comfort & Delight)
• …function of a building: “Provide the desired environment
for human use and occupancy”
“Durability, Convenience, and Beauty” Vitruvius, 70 BC
Building Science
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Building Components
• Buildings are made of several large systems • Can be grouped in four categories
– Superstructure – Service Systems – Fabric – Enclosure
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Importance of the Enclosure
• Image – People see it!
• Building problems – Often heat, moisture and the enclosure
• Energy consumption – Driven by enclosure performance
• Durability often less than building – Roof 15-30 yrs, Windows 20-40 yrs
Sealants 5-25 yrs Building Science
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The Enclosure: An Environmental Separator • The part of the building that physically separates the interior and exterior environments.
• Includes all of the parts that make up the wall, window, roof, floor, etc… from the innermost to the outermost layer.
• Sometimes, interior partition also are environmental separators (pools, rinks, etc.)
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Building Enclosure Components
We will cover: roofs, walls, basements/slabs and windows
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Enclosure Loadings
• The separation function generates loads • Load: any event, phenomenon or
characteristic that can affect the enclosure – Heat, Air, Moisture – Fire, Sound – UV, Ozone – Gravity, impacts, abrasion – Insects – Etc…
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Loads: Climate / Site
• Design for – Climate zone – Site – Building height, shape, complexity
Building Science
Marcus Vitruvius Pollio
These are properly designed, when due regard is had to the country and climate in which they are erected. For the method of building which is suited to Egypt would be very improper in Spain, and that in use in Pontus would be absurd at Rome: so in other parts of the world a style suitable to one climate, would be very unsuitable to another: for one part of the world is under the sun's course, another is distant from it, and another, between the two, is temperate.
Seattle ≠ Sacramento Miami ≠ Minneapolis Edmonton ≠ Vancouver
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Canada:
Significant heating demand, in lots of places
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HDD 18C
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Climate Zones
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Climate Load Modification
• Building & Site (overhangs, trees…) – Creates microclimate
• Building Enclosure (walls, windows, roof…) – Separates climates – Passive modification
• Building Environmental Systems (HVAC…) – Active modification – Use energy to change indoor weather
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Evolution
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Residential
Commercial
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Basic Functions of the Enclosure
• 1. Support – Resist and transfer physical forces from inside and
out • 2. Control
– Control mass and energy flows • 3. Finish
– Interior and exterior surfaces for people
• Distribution – a building function
Building Science
Functional Layers
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Basic Enclosure Functions
• Support – Resist & transfer physical forces from inside and
out • Lateral (wind, earthquake) • Gravity (snow, dead, use) • Rheological (shrink, swell) • Impact, wear, abrasion
• Control – Control mass and energy flows
• Finish – Interior and exterior surfaces for people
Building Science
Functional Layers
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Basic Enclosure Functions • Support
– Resist & transfer physical forces from inside and out • Control
– Control mass and energy flows • Rain (and soil moisture)
– Drainage plane, capillary break, etc. • Air
– Continuous air barrier • Heat
– Continuous layer of insulation • Vapor
– Balance of wetting/drying • Finish
– Interior and exterior surfaces for people
Building Science
Functional Layers
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Other Control Functions . . .
• Support • Control
– Fire • Penetration • Propagation
– Sound • Penetration • Reflection
– Light • Diffuse/glare • View
• Finish
Building Science
Functional Layers
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History of Control Functions
• Older Buildings – One layer does
everything
• Newer Building – Separate layers, . . . separate functions
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Basic Enclosure Functions
• Support – Resist & transfer physical forces from inside and out
• Control – Control mass and energy flows
• Finish – Interior & exterior surfaces for people
• Color, speculance • Pattern, texture
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Functional Layers
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Finish vs. Control Confusion
What is the gypsum board for? Distribution
• A Building Function imposed on enclosure • Distribute services or utilities to from through,
within, the enclosure, e.g., – Power – Communication – Water (Potable, sewage, etc.) – Gas – Conditioned air – Cold or hot water
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Enclosure Design Principles 1
• Design a complete structural load transfer path – Structure, windows, ties, etc – All loads go to ground
• Understand site, use, and climate loadings – Rain, sun, high rise or low-rise, pool, office, school
• Continuous rain control plane – Control with surface features and detailing – Drained, storage, or perfect barrier strategy
• Continuous plane of air barrier tightness – Fastidious attention to detail 3-D
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Enclosure Design Principles 2 • Provide a continuous plane of insulation
– Ideally separate structure from enclosure – Avoid thermal bridges
• Provide a moisture tolerant design – Balance wetting, drying, and storage (matl’s, climate) – Use appropriate levels of vapour control
• No cold vapor barriers, allow drying
• Accommodate movements and tolerances • Draw all of the Details!
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• Structure
• Air-Rain Barrier
• Insulation
• Finish
The Enclosure: Adding the Layers
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Building Science 2008
Framed Enclosures: Adding the Layers
Structure Air Flow Control Insulation Rain Control Finish
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1. Air / Rain Barrier 2. Structural Support 3. Rain Shedding 4. Insulation
Design Information older than I am. What is a high performance enclosure?
• High levels of control • But, poor continuity limits performance • & Poor continuity causes most problems too:
– E.g. air leakage condensation – Rain leakage – Surface condensation – Cold windows
• Thus: continuity + high levels of control
www.BuildingScience.com
High Performance
• No leaks = continuous = no holes 1. Rain 2. Air 3. Thermal
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“Rainscreen” or “Drained” System
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Window
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Enclosure Design: Details
• Details demand the same approach as the enclosure.
• Scaled drawings required at
- change in plane - change in material - change in trade
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Plan Dimensions
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Baseplate usually wider than column at the critical base plate Building Science .com
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Building Science .com Building Science .com
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Perfect Wall
• CMU backup
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Asphalt Drainage Plane Air Barrier Rockwool Insulation
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Building Science
The Commercial Steel Frame High Performance wall
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Perfect Wall on Steel stud
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Transitions, Continuity, Penetrations
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Sprayfoam Control Layer
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Attachment
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The Compromise Wood Frame High R-value wall
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• Discontinuous thermal and air barrier
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Wood Framed Furring 2x6 w/R5 exterior is a start 2x4 w/R7.5 for higher interior RH 2x6 w/R10-R15 is likely long-term answer
Increasing ratio of Exterior to Cavity insulation reduces risk and improves performance
Cladding attachments
• Insulating on exterior is not a structural challenge … unless you use the wrong model
• Bending does matter, but only at high deflections
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Foam sheathing field testing Foam sheathing lab testing
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4’ x 8’ panel, 14 #10 screws 65 lb/screw @ 1/32” deflection
“Flow through” wall. Allows fast drying in both directions
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Rockwool 1x3 furring @ 24” o.c. #10 screws @ 16” o.c. vertically Result: 20 psf cladding weight with < 2/100” deflection
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Houses
• Rain • Heat • Air
www.buildingscience.com has many different enclosure sections
Perfect wall variation • Except at
joints
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Building Science
Metal Panels Furring
• Commercially available
• Only fasteners penetrate insulation
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Recall: Enclosure Functions • Support
– Resist & transfer physical forces from inside and out • Control
– Control mass and energy flows • Rain (and soil moisture)
– Drainage plane, capillary break, etc. • Air
– Continuous air barrier • Heat
– Continuous layer of insulation • Vapor
– Balance of wetting/drying • Finish
– Interior and exterior surfaces for people
Building Science
Functional Layers
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