green roofs: multi-functional environmental protection...

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



Omaru Creek, Glen InnesFlooding Issues

Omaru Creek, Glen InnesHigh‐flow impacts from every‐day storm events



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



USAChicago City Hall

London: Canary Wharf

Tube Station



ChinaShanghai

WuhanBeijing

Thailand

Lumpini Park, Bangkok

Bhubing Palace, Chiang Mai



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



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



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)



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



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



Questions?

green roofs: multi-functional environmental protection...

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