The

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The Dirt on Green Roofsa detailed look at
green roofs

• Jamie McKay, P.Eng.
• Associate, Project Engineer, Leed A.P.
• M O R R I S O N H E R S H F I E L D
• www.morrisonhershfield.com
• Ottawa Toronto Calgary
  Edmonton Vancouver Atlanta
  Seattle Fort Lauderdale

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Overview

• Benefits of Green Roofs
• Design Considerations
• General Considerations
• Proprietary vs. Custom
• Green Roof System overview Review of Each
  component
• Details
• LEED Implications
• Construction Considerations
• Quality Assurance
• Leak Detection
• Maintenance Operations Considerations

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Green Roof Benefits

• Social Benefits
• Storm-water retention and water filtering
• Reduced heat island effects
• Habitat and biodiversity improvements
• Air cleansing and carbon sink
• Owners 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
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Design Considerations

• General Design Considerations
• 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

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Design Considerations

• Proprietary System
• Pros
• Technical support
• Faster installation
• Warranty
• Less plant replacement lower maintenance
• Lighter weight
• Cons
• Higher capital cost
• Limited options

• vs. Custom Built
• Pros
• Reduced system cost
• Increased plant selection and customizing
• Cons
• Warranty
• Weight increase
• Plant replacement/Maintenance increase
• Coordination issues
• Increased Design fees

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Design Considerations

• Examples of Proprietary Systems
• Sopranature (Soprema)
• Garden Roof (Hydrotech)
• Sky Garden (Green Roof Tops)
• Greengrid
• Elevated Landscape Technologies
• Xero Flor (vegetated blanket)
• ZinCo (Mat and blanket)

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Design Considerations

• System Overview
• 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/ec
oli/Greenroof/benefits.html
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Design Considerations

• Vegetation Growing Medium
• The Green Roofs 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
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Design Considerations

• Water Drainage Storage
• 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
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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
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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
• 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 NRC, Institute for Research in
Construction
Photos courtesy of soprema
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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
• 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

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Design Considerations

• Membrane types
• Multi-layer systems (SBS, BUR, Hot liquid, cold
  liquid).
• Attachment methods
• Torch-applied
• Mechanically fastened
• Hot mopped
• Cold mopped
• Adhesive
• Pros Durable (longer life/thicker systems)
• Cons Higher cost, Fire/Insurance issues, slower
  install, aesthetics

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Design Considerations

• Membrane types
• 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

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Design Considerations
LEEDCanadaTM Credits Related to Green Roofs

• Sustainable Sites
• Credit 5 Reduced Site Disturbances
• Credit 6 Stormwater Management
• Credit 7 Heat Island Effect
• Water Efficiency
• Credit 1 Water Efficient Landscaping
• Credit 2 Innovative Wastewater Technologies
• Credit 3 Water Use Reduction
• Energy Atmosphere
• Credit 1 Optimize Energy Performance

• Material Resources
• Credit 3 Resource Reuse
• Credit 4 Recycled Content
• Credit 5 Regional Materials
• Credit 6 Rapidly Renewable Materials
• Credit 8 Durability
• Indoor Environmental Quality
• Credit 7 Thermal Comfort
• Innovation and Design Process
• Credit 1 Innovation in Design

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Design Considerations

• Details
• Almost all leaks occur at transitions,
  penetrations The details
• Designers need to consider
• Supplementary Drawing/Detail/Specification review
  (BEP, Manufacturer, roofing trade)
• Integrated Design with Architectural, Structural,
  Mechanical, Plumbing, Electrical, and Landscape
• Drawings for specific details
• Roof edge (parapets transitions)
• Penetrations (incl. mechanical)
• Division walls
• Accessible areas
• Ponds

Drawing courtesy of PWL, dockside Green, Victoria
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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
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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
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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
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Construction Considerations

• Quality Assurance Methods
• Mock-ups
• Testing (adhesion, thickness, etc.)
• Enhanced Field Review
• Manufacturer representatives field reports
• Flood Tests
• Leak Detection systems

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Construction Considerations

• Leak Detection systems
• Electric Field Vector Mapping
• Infrared Scans
• Electric tracing monitoring systems

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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
• 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
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