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Kees Govers presents Green Roofs
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Green Roof Systems
Kees Govers
LiveRoof Ontario Inc
Mt Brydges, ON
What you need to know to implement effective green roofs
Green Roof Basics
Extensive green roof systems
Evaluating green roof systems
Design tips
An installation in 4 slides
Innovative new greening techniques
Questions
Main reasons for installing green roofs
Stormwater management
Air pollution reduction
Urban heat island reduction
Energy use reduction
Replacement or increase of green space
Roof life extension
Aesthetics
Green roof mandates
Contribution to LEED credits
What makes a green roof work?
Plants utilise solar radiation Photosynthesis creates carbohydrates and O2 from
H2O and CO2
Respiration produces plant growth and CO2
Respiration and photosynthesis create transpiration
Transpiration draws H2O and O2 from substrate along with nutrients
Growing medium absorbs and holds H2O and O2 until transpired
Filtration and buffering takes place in the process
LEED Sustainable Sites Credits 6.1 & 6.2 Stormwater Design: Quantity control & Quality control
Storm Water Retention
Storm Water Detention
Storm Water Filtration
Storm Water Retention Defined by the absorptive capacity of
Green roof system
Growing media 20-45% by volume
Plants depends on plant type and turgidity
Water retention fabrics
Water retention cups
Green roof system auxiliaries
Cisterns
Where does the retained water go?
Evapotranspiration
Succulents (facultative CAM)
Grasses (mostly C-4)
Perennials (mostly C-3)
Photosynthesis
Surface evaporation
What happens during a drought?
Succulents
Switch to CAM
Reduce evapotranspiration
Cuticles get thicker
Plants physically shrink
Plants loose mass (mostly water)
Death occurs after very long drought
Recovery time from drought: less than 24 hours
Sedum ellacombianum
Allium schoenoprasum ‘Forescate’
What happens during a drought
Grasses (C-4)
Reduce evapotranspiration
Cuticles get thicker
Plants abort flowers and seeds
Plants shrivel up
Plant crown goes dormant
Death occurs after variable fairly long drought
Recovery time from drought: up to several weeks
Koeleria macrantha
Schyzachyrium scoparium
What happens during a drought
Perennials (C-3)
Reduce evapotranspiration
Cuticles get thicker
Plants abort flowers and seeds
Plants shrivel up
Plant crown goes dormant
Death occurs after variable length drought
Recovery time from drought: weeks to months
Penstemon digitalis Aquilegia canadensis
Stormwater detention and filtration
Effectiveness depends on
Stormwater retention
Rainfall intensity
Saturated conductivity of growing medium
Plant density
Denser plantings prevent surface runoff
Storm water quality improvement
Buffers water pH
Filters pollutants
Organic compounds
Heavy metals
Particulate matter
Reduction by deposition on foliage
Particularly effective for
Particulates
NO, NO2
2011 Lancaster University Study
Particulates up to 60% reduction
NO, NO2 up to 40% reduction
Sustainable Sites credit 7.2 Heat island Effect: Roof
Lower roof temperatures Reduced heat transfer into buildings
Lower HVAC loads
Reduced roofing membrane stress
Improved photo voltaic cell performance
Lower temperatures above the roof
How does a green roof compare to a white roof?
Lower surface temperature in the summer sun
Higher temperature in the winter
Effectiveness does not depend on cleanliness
Does not cause glare
Does not bounce solar radiation to other surfaces
Does not deteriorate under UV light
Intensive Extensive
Growing medium depth 300mm and deeper 65mm to 150mm
Saturated load 400 kg/m2 and over 50 – 250 kg/m2
Plants Trees and shrubs Succulents, grasses, perennials
Maintenance High low
Irrigation Always Depends on design
Four critical factors Drainage
Growing medium
Plants
Plant coverage
Nothing else matters A stressed green roof doesn’t function properly!
A dead green roof doesn’t function !!!!
Built in place systems
Pre-grown blankets
Modules
Hybrid Modules
Stoney Creek Library London
27
• Built up system • Hand planted • Slow growing due to heat and cold • Vulnerable to weeds • High maintenance
Grand Rapids, MI 1 yr old
Ottawa, ON, 1 season old
29
• Takes a long time to grow in • Mini monocultures of deciduous plants leave soil exposed • Lacks succession in design
MEC 1998 Mature built in place green roofs
CMC Gatineau
Blanket system assembly
Blanket installation
Blankets as part of a built in place system
What industry wide protocols exist? 5 ASTM Standards (All based on German FLL Standard)
ASTM E2396-05 standard test method for saturated permeability of granular drainage media
ASTME2397-05 Standard practice for determination of dead loads and live loads associated with green roof systems
ASTM E2398-05 Standard Test method for water capture and media retention of geocomposite drain layers for green roof systems
ASTM E2399-05 Standard Test method for maximum media Density for dead load analysis of green roof systems
ASTM E2400-06 Standard guide for selection, installation and maintenance of green roof systems
Toronto Green Roof Standard
Only comprehensive enforceable green roof standard in North America
FM Global approvals standard 4477 for vegetative roof systems
FLL Guideline for the planning, execution and upkeep of green roof sites, release 2008
Drainage
Growing Media
Plant Selections
Edge effect
Irrigation
Wind uplift performance
Maintenance requirements
Typical drainage layers For built in place
Typical drain layer used under mats
Engineered growing medium
•Designed to remain on the roof, very durable
•No stabilizing agents should be needed
•No short term lightweight fillers •No perlite or vermiculite
•No horticultural foam or Styrofoam beads
•No more than 5-6% organic matter (by pyrolysis test)
•No hydrogels (not legal in Canada for growing media)
• Falls within FLL Standard parameters
Poor Growing medium choice •Too coarse •Too little organic matter •Tough for plants to establish
Poor Growing medium choice •Too much organic matter •Poor aeration when saturated
April 2010
May 2010
Plants grow too fast initially Plants start dying after about 4-5 years
Very shallow growing medium
Growing media specifications
Be as specific as you can
Demand an FLL test report
At time of submission
Just prior to installation
For modules at time of filling
Ask for physical samples
Only accept substitutions is they meet the above criteria
Get to know your supplier and their suppliers
Plant producer Quality of plants
Propagation facilities
Production capacity
Handling equipment
Delivery equipment (for module suppliers)
Installation equipment Blower trucks
Conveyor belts
Delivery racks
Stock beds
Production Capacity and equipment
Depends on:
Depth of growing medium
Design of the green roof
Intended purpose of the green roof
Irrigation or not
Succulents Grasses Perennials
Media <75mm With irrigation no No
Media 75 to 150mm yes With irrigation With irrigation
Media >150mm yes some some
Combination plantings are preferred • Better winter survival • Better drought survival • Healthier plants
Succulents Grasses Perennials
Seed Takes a long time
yes some
Cuttings Small window no No
Plugs Spring and fall Spring and fall Spring and fall
mats Spring and fall Spring and fall no
Pregrown modules Above 2 C Above 2 C Above 2 C
Plant installation limitations
150mm depth, no irrigation • Aster • Solidago • Juniperus horizontalis • Scabiosa • Geranium • Sedums • Alliums • Sempervivums • Calamintha • Nepeta • Agastache
Regional LiveRoof Plant Selections Guide
2006 Timber Press Snodgrass&Snodgrass Best North American book on extensive green roofs
Eglinton West Station
Victoria Park Station
Stoney Creek YMCA & Library, London
Toronto City Hall podium
68
• Exposed Edges
• No soil connectivity
• Plants dry out along edges
• Plant roots are affected by cold
• Slower growth as a result
69
• Exposed plastic and gaps between modules negatively affect plant performance
Michigan State research (to be presented at CitiesAlive)
Based on 30 minute irrigation events
Overhead irrigation 25% more water applied than drip or sub
20-30% run-off of total applied
Even distribution
Drip irrigation 25% less water applied
80% plus run-off of total applied
Poor distribution
Sub irrigation Worse in all respects than sprinkler or drip
Drip lines with 6” spacing (normal is 12”)
After 10 minutes
After 60 minutes
Waste water
Appropriate use of drip irrigation
Drip irrigation failure
Relative costs and embedded energy Line spacing
Sub: under entire green roof system
Drip: 300mm spacing between lines
Sprinkler: Up to 12 metre spacing between lines
Installed cost in TO Sub: $40 -$60/m2
Drip: $20-$35/m2
Sprinkler: $15-$20/m2
Maintenance Sub: near impossible
Drip: clogged lines need to be replaced
Sprinkler: easy maintenance and malfunction detection
City of Toronto requires Wind uplift study of each building according to OBC
signed by a professional engineer
Wind uplift pressures in kPa (or psf)
2015 version of National Building code will require wind uplift rating for: Roofing systems HVAC units PV installations Green roofs Pavers
How wind uplift pressure is calculated:
Formulas in OBC
Mathematical exercise
Scale wind tunnel testing
Usually done for building models of unusual shape
Full size dynamic testing
Testing on full scale products
Test protocol developed by NRC Canada
CSA A123.21-10
CSA A123.21-10
Dynamic wind uplift test protocol
Test rating may be required for all green roof systems.
Untested systems will be rated at dry weight of system
Only one system tested to date.
Regent Park Block 24
Mature plants resist scour
Low maintenance planting
Medium maintenance planting
High maintenance planting
High maintenance
Nutrition
Preliminary findings at U of G
Maintenance concentration of macro nutrient important
Source of nutrients is unimportant
Healthiest plants at modest levels of nutrition
Starving plants does not toughen them
Overfeeding plants kills them
Install pavers, edging and irrigation before the plantings
Overhanging roofs require irrigation
Stone Pavers Installed against a South Facing Wall
Prevent scorching
Roof with Exposed Membrane Roof without Exposed Membrane
Distressed and Dead Plants Due to Excessive Foot Traffic
Severe traffic damage by other trades Avoidable by proper sequencing
Plant Death Caused by Roof Vent Air stream
Roof Access Point with Stone Pavers
The Blank Canvas
•membrane replaced
•EFVM installed
•Asphalt flood coat applied
Installation Day 1
Installation End of Day 2
Installation End of Day 4
Greening can happen anywhere on any scale
Exercise due diligence in selection and execution
Don’t be afraid of innovative ideas
Contact Information Kees Govers LiveRoof Ontario Inc 23078 Adelaide Rd Mount Brydges, ON N0L 1R0 Canada (519) 245-4039 [email protected] www.LiveRoof.ca
Toronto Police Academy