Green Roofs Overview

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 kees@liveroofontario.ca www.LiveRoof.ca

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