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Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 1
Green Roofs: Multi-Functional Environmental Protection TechnologyElizabeth Fassman Ph DElizabeth Fassman, Ph.D.Department of Civil and Environmental EngineeringUniversity of Auckland
Robyn Simcock, Ph.D.Landcare Research
Professor Mohammed FaridDepartment of Chemical and Materials EngineeringUniversity of Auckland
29 July 2009
y
Current Students:Ph.D. Candidate: Emily VoydeMEngSt: Julien Bianchi, Sarah Bouassida, Marie-Helene Ponsard, Luc Welfringer
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 2
Omaru Creek, Glen InnesFlooding Issues
Omaru Creek, Glen InnesHigh‐flow impacts from every‐day storm events
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 3
Sources of Water Quality Impacts from Urban Development
Catchpit on Symonds St
Garfield Rd, Parnell
Low Impact Design (LID) in Portland (Oregon, USA) South Waterfront
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 4
USAChicago City Hall
London: Canary Wharf
Tube Station
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 5
ChinaShanghai
WuhanBeijing
Thailand
Lumpini Park, Bangkok
Bhubing Palace, Chiang Mai
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 6
Miruwai toilet block
New Zealand
London
Waitakere City Civic Centre
Kawakawa Hundertwasserpublic toilet
Waitakere City Civic Centre
• Reduce building energy consumption by providing thermal mass and insulationMiti t th “ b h t i l d” ff t (i l bi t
Potential Benefits
• Mitigate the “urban heat island” effect (ie lower ambient temperatures from plant transpiration)
• Reduce stormwater runoff volume & flow rate• Absorb airborne pollutants• Protect roof surface from damaging UV rays & cracks caused by
flexing with temperature fluctuation• Create urban habitat• Provide amenity & aesthetic value
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 7
Extensive Green Roof System Components
Vegetation
m
Vegetation•Reduces absorption of solar radiation
•Cools surrounding air•Intercepts rainfall•Prevents substrate migration.
Substrate•Supports plants (physically and nutritionally)
•Stores precipitation•Extends flow path•Provides insulation and/or thermal massDrainage Layer
P o ides f ee d ainage fo
<150 m
•Provides free drainage for precipitation in excess of system storage capacity
•Geotextile supports substrate & prevents migration
•Provides air for plants
Waterproof Membrane
•Protects structure from water damage
•May include multiple layers, including a root barrier
Test Site: Roof of UoA School of Engineering
Downtown Auckland Cityy
UoA School of Engineering
• Total roof area ~250 m2
• Greened area ~ 234 m2
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 8
Research Objectives
Stormwater Management
Habitat & Biodiversity• Determine green roof design to mitigate stormwater runoff
Plant Development and Maintenance
Climate & EnergyDetermine green roof design to mitigate stormwater runoff under local climate conditions.
- Storage of 10-20 mm precipitation (i.e., no runoff from “everyday” events.)
- Monitor and model hydrologic budget for engineering guidance.• Develop system suitable for new and retrofit construction.
– Dry bulk density < 800 kg/m3
– Wet system weight < 100 kg/m2
• Identify suitable and evaluate effectiveness of locally available materials vs. “proven” materials used overseas.
• System should be as “easy” as possible (i.e. low maintenance, no irrigation).
100%
Results to Date: Engineering Green Roof
40%
50%
60%
70%
80%
90%
Red
uction
89 storms over 7 months
630 mm rainfall
~96% reduction in peak flow rate
75% of rainfall doesn’t become runoff (literature values: 50-68%
0%
10%
20%
30%
0 50 100 150 200
Rainfall Depth (mm)
50 mm peak reduction
70 mm peak reduction
50 mm retention
70 mm retention
runoff (literature values: 50 68% retention)
~99% retention for storms less than 25 mm (water quality storm)
0 difference between 50 mm and 70 mm system for stormwater control (plants thriving in 70 mm)
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 9
Surface Temperature: Winter 2008
August September
13
14
15
16
17
18
19
Tempe
rature (oC)
Greened Surface
Reference Surface
Ambient (820 mm)
13
14
15
16
17
18
19
Tempe
rature (oC)
Greened Surface
Reference Surface
Ambient (820 mm)
August September
Statistically significant differences.
Peak temp time delay.
Duration of elevated temp.
10
11
12
0:00 12:00 0:00Time of Day
10
11
12
0:00 12:00 0:00Time of Day
Evidence of vertical gradient (surface vs 750 mm).
Evidence of vertical gradient (surface vs 750 mm).
Evidence of Energy Benefits
• Insulation is significant• Insulation is significant(Akbari et al. 2001; Alexandri and Jones 2007; Connelly and Liu 2005; Liu and Baskaran 2003; Takebayashi and Moriyama 2007)
• Reduction in heat flow from a building by 70-80%, thereby reducing heating and/or cooling energy demand(Akbari et al 2001; Connelly and Lui 2005)
• Creation of microclimate significantly reduces surface air temperature (Connelly and Liu 2005; Environmental Affairs Department 2006; Takebayashi and Moriyama 2007)2006; Takebayashi and Moriyama 2007).– increase air conditioner efficiency (Liu 2003)– mitigate urban heat island effect (Environmental Affairs Department 2006;
Sailor and Dietsch 2007; Voogt 2004)
• Incorporated into EnergyPlus model in LEED (USA) (Sailor 2008)
• Auckland green roofs… watch this space
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 10
Conclusions to date• Green roofs provide opportunities for multiple environmental
benefits from a single technologybenefits from a single technology.– Stormwater control reduces erosion potential in streams, transport of
contaminants, and potential for combined sewer overflow.– Thermal mass and insulation passively reduces energy demand for heating and
cooling.
• A long period of monitoring is necessary to fully understand the complex behaviour of an EGR for stormwater control and energy demand mitigation, but results to date are promising.
• Design manual due to be published by Auckland Regional Council,g p y g ,hopefully later this year (draft is under review).
Acknowledgements
• Technicians and students in CEE Dept at UoA and technicians from Landcare R hResearch
• Prof. Peter Brothers• Mr. Earl Shaver
Dr. Elizabeth Fassman 29/07/2009
Dept of Civil and Environmental Engineering 11
Questions?