Transcript The “Dirt” on Green Roofs

The “Dirt” on Green Roofs:
a detailed look at green roofs
Jamie McKay, P.Eng.
Associate, Project Engineer, Leed A.P.
M ORRISON H ERSHFIELD
www.morrisonhershfield.com
Ottawa
Toronto
Calgary
Edmonton
Vancouver
Atlanta
Seattle
Fort Lauderdale
Overview
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Benefits of Green Roofs
Design Considerations
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General Considerations
Proprietary vs. Custom
Green Roof System overview Review of Each component
Details
LEED Implications
Construction Considerations
– Quality Assurance
– Leak Detection
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Maintenance & Operations Considerations
Green Roof Benefits
Social Benefits
 Storm-water retention and water
filtering
 Reduced heat island effects
 Habitat and biodiversity improvements
 Air cleansing and carbon sink
Owner’s Benefits
 Roof membrane protection & life
extension (reduce temperature
fluctuations and physical damage)
 Sound insulation
 Occupant benefits (therapeutic and
added useable space).
 Increased property value
Naturescaping, City of North Vancouver
Design Considerations
General Design Considerations
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Consultant Roles & IDP (Architect, Structural, Envelope, Landscape,
Mechanical, etc.)
New Construction vs. Existing Building (Structural limitations)
Building Height, Exposure and Surrounding Buildings (Sun, Wind, Shading,
fire)
Accessible or non-accessible (Safety)
Intended use (water collection and filtering, urban garden, habitat
protection/promotion, sitting/walking areas, etc.)
Plant Selection (soil depth, irrigation, maintenance, component affects)
Budget (initial and operating)
Proprietary systems vs. Custom Built
Design Considerations
Proprietary System
vs. Custom Built
Pros:
Pros:
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Technical support
Faster installation
Warranty
Less plant replacement &
lower maintenance
Lighter weight
Cons:
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Higher capital cost
Limited options
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Reduced system cost
Increased plant selection and
customizing
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Cons:
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Warranty
Weight increase
Plant replacement/Maintenance increase
Coordination issues
Increased Design fees
Design Considerations
Examples of Proprietary
Systems
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Sopranature (Soprema)
Garden Roof (Hydrotech)
Sky Garden (Green Roof Tops)
Greengrid
Elevated Landscape
Technologies
Xero Flor (vegetated blanket)
ZinCo (Mat and blanket)
Design Considerations
System Overview
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Vegetation
Growing medium
Water
storage/absorption/drainage
Root Barrier
Insulation (if required)
Roofing membrane
Structural support
Photo courtesy of: http://www.uwm.edu/Dept/GLWI/ecoli/Greenroof/benefits.html
Design Considerations
Vegetation & Growing Medium
The Green Roof’s intended function will
typically dictate the vegetation selection.
There are two main categories:
Extensive
–Thin growing material
–Little or no irrigation (except set-up)
–Low plant diversity
–Light weight
–Low maintenance
–Typically not accessible to public
–Lower capital cost
Intensive
–Deep soil
–Irrigation typically required
–High plant diversity
–Heavy weight
–Accessible to public
–Higher capital cost
Photos courtesy of BuildSmart
Design Considerations
Water Drainage & Storage
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Allow free drainage of water
under growing medium and
above roofing membrane
Provide storage space for
excess water, which reduces
need for irrigation
Allow aeration of soil, which
reduces cultivation needs and
maintenance costs
Photos courtesy of Greenrooftops.com
Design Considerations
Root Barrier
An often overlooked, but critical component
of a green roof assembly. A poor root barrier
can substantially shorten the life of the roof.
The selection is typically based on:
 Plant selection
 Soil depth or use of gravel or voiding
material
 Proprietary vs. custom built assemblies
 Chemical or non-chemical treatment
 Sensitivity of underlying structure
 Membrane selection (monolithic vs. sheet)
Photos courtesy of Greenrooftops.com
Photos courtesy of zinco.ca
Design Considerations
Insulation
Insulation placement is dictated
mostly by design requirements and
philosophy.
There are two main categories:
Conventional Roof
Insulation placement under roofing
membrane, which requires:
-A separate air and vapour barrier
-Air barrier tie-in with walls
-Recovery board
-Maintenance paths
Photos courtesy of NRC, Institute for Research in Construction
Inverted Roof
Insulation installed over roofing
membrane, which requires:
-Ballast to withstand insulation uplift
-Two level drains
-Higher vents, parapets and upturns
Photos courtesy of soprema
Design Considerations
Roofing Membranes
The roofing membrane needs to be carefully selected based on
durability and lifespan. Once covered it will not be easily
serviced.
Design Considerations:
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Structure (wood, steel, concrete)
Membrane durability (thickness & adhesion)
Weather & installation conditions (wet, cold, dusty)
Visible at parapet walls (UV stabilized)
Compatibility with adjacent materials
Maintenance, renewals, embodied energy, cradle to cradle/grave, regional
materials, recycled content
– Historical performance
– Skilled workforce
– Warranty requirements
Design Considerations
Membrane types:
Multi-layer systems (SBS, BUR,
Hot liquid, cold liquid).
 Attachment methods:
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– Torch-applied
– Mechanically fastened
– Hot mopped
– Cold mopped
– Adhesive
Pros: Durable (longer life/thicker
systems)
Cons: Higher cost, Fire/Insurance issues,
slower install, aesthetics
Design Considerations
Membrane types:
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Single layer sheet systems
(PVC, TPO, EPDM).
Attachment methods:
– Mechanically fastened & welded
– Adhesive & welded
Pros: Less cost, Less insurance issues,
architectural (exposed), faster install
Cons: Less expected life, thinner
systems
Design Considerations
LEEDCanada Credits Related to Green Roofs
TM
Sustainable Sites
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Credit 5: Reduced Site Disturbances
Credit 6: Stormwater Management
Credit 7: Heat Island Effect
Water Efficiency
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Credit 1: Water Efficient Landscaping
Credit 2: Innovative Wastewater
Technologies
Credit 3: Water Use Reduction
Energy & Atmosphere
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Credit 1: Optimize Energy Performance
Material & Resources
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Credit 3: Resource Reuse
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Credit 4: Recycled Content
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Credit 5: Regional Materials
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Credit 6: Rapidly Renewable Materials
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Credit 8: Durability
Indoor Environmental Quality
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Credit 7: Thermal Comfort
Innovation and Design Process
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Credit 1: Innovation in Design
Design Considerations
Details
Almost all leaks occur at transitions,
penetrations – “The details”
Designers need to consider:
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Supplementary Drawing/Detail/Specification
review (BEP, Manufacturer, roofing trade)
Integrated Design with Architectural, Structural,
Mechanical, Plumbing, Electrical, and Landscape
Drawings for specific details:
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Roof edge (parapets & transitions)
Penetrations (incl. mechanical)
Division walls
Accessible areas
Ponds
Drawing courtesy of PWL, dockside Green, Victoria
Design Considerations
Sloped Green Roofs
 Typically less than 30º
 Requires soil stabilizing
structure
 Orientation and shading
consideration
 Specific plants and root
structure
 Perimeter edge drainage
 Access for maintenance
Photos courtesy of Greenrooftops.com
Design Considerations
Photos courtesy of soprema
Roof Edge Details
The roof perimeter specifics:
 Be accessible for building
maintenance, to control plant growth,
and add fire breaks (where required)
 Include concrete or similar perimeter
curbs to enclose vegetation (should
be moisture tolerant)
 Include rock ballast or pavers
(inverted roofs)
 Include guard rails for accessible
roofs
Photos courtesy of Calhoun school, NY
Design Considerations
Roof Penetrations
Similar to roof perimeters, penetrations
require separation from vegetation.
Design Considerations include:
 Two stage drains and extra high access
collars
 Roof anchors and safety lifeline paths.
 Irrigation lines
 Electrical conduit
 Skylights & Access hatches
 Railings, fixed curbs, benches,
playground equipment
Photos courtesy of www.miller-roofscapes.co.uk
Drawing courtesy of PWL, dockside Green, Victoria
Construction Considerations
Quality Assurance Methods
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Mock-ups
Testing (adhesion, thickness, etc.)
Enhanced Field Review
Manufacturer representative’s field reports
Flood Tests
Leak Detection systems
Construction Considerations
Leak Detection systems
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Electric Field Vector Mapping
Infrared Scans
Electric tracing & monitoring
systems
Maintenance & Operations
Considerations
A maintenance and renewals plan should be developed for the building to
assist the Owners/Tenants with M/O requirements and future replacement.
The following should be considered for maintaining and operating a green
roof:
Vegetation
Plant selection (roots, watering (initial vs. continued), sun/shade sensitivity, weed tolerance,
prevailing winds, etc.). What will happen to them when the roofing assembly requires
replacement? Repairs?
 Available access (personnel, material removal and addition for repair/replacement, etc.).
 Knowledgeable maintenance staff or hired maintenance group
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Roof membrane
Periodic review of membrane? How? Leak monitoring? EFVM?
 Drains are clean, and penetrations are clear
 Review for ponding
 Warranty requirements?
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Show Case
Vancouver Public Library
Fairmount Hotel, Vancouver
Ballard Library, Seattle
The Palais Omnisports de Paris-Bercy in France
Brinkoplan, Den Helder, The Netherlands
Vancouver Convention Centre Expansion