Green roofs in urban areas

Urban Ecology Research Group,Botanic Garden University of Helsinki

Background to recap!Background – to recap!• Green roofs (rooftop gardens, vegetative roofs, ecoroofs) improve Green roofs (rooftop gardens, vegetative roofs, ecoroofs) improve

living conditions in the city

• LID (low-impact development)

• Ecosystem service– regulating, provisioning, cultural

• Advantages;– Rainwater retention (stormwater runoff)– Passive heating/cooling of buildings (energy savings)Passive heating/cooling of buildings (energy savings)– Thermal benefits to the surroundings (microclimate, urban heat island effect)– CO2 sequestration– Habitat provision (’recover greenspace’)

Dust/pollution filtering– Dust/pollution filtering– Gardening/food production– Increase longevity of roofing membranes– Recreation, Education

A th ti– Aesthetics– Noise reduction– Business opportunities (nurseries, contractors, industry)

Hobbiton, Middle-Earth (http://www.the-shire.eu/Hobbiton.jpg)

Examplesp

Sod/turf roofs from ScandinaviaSod/turf roofs from Scandinavia

Chicago City Hall, USA

ACROS F k k B ildi JACROS Fukouka Building, Japan

Singapore

All pics from: http://egardens.blogspot.com/2009/03/green-roofs-more.html

Residential application

Scientific literatureScientific literature• Earliest study in ISI = 1996

• 181 articles (99 in scientific journals)

• Main subjects– Thermal (cooling/heating), Energy = 29– Water (stormwater, infiltration, etc.) = 25– Vegetation = 15Vegetation 15– Cost/benefit, design, policy = 15– Substrate depth, type = 14– Biodiversity = 3

Pollution = 3– Pollution = 3– Ecosystem services = 2– Sound = 2

1520

• Countries– Germany, USA, Canada– ...closer to home: Sweden

• Stormwater vegetation (Sedum-moss) substrate N P

Num

ber o

f stu

dies

510

Stormwater, vegetation (Sedum moss), substrate, N, P

1996 1998 2000 2002 2004 2006 2008 2010

Year

0

Main types of Green roofs (Europe)Main types of Green roofs (Europe)

E t i• Extensive– Substrate layer max of 150 mm

Sedum species– Sedum species– Can be on sloped roofs (up to 45o)

• IntensiveSubstrate layer more than 150 mm– Substrate layer more than 150 mm

– Grasses, perennial herbs, shrubs– Slope less than 10o– Slope less than 10– Can be used as roof gardens

Intensive roofs

Extensive roofsExtensive roofs

Oberndorfer et al. 2007. BioScience

The problemThe problem...I t b i ti + i filli hi h % • Intense urbanisation + infilling = higher % impermeable surfaces per area (up to 50% and more in cities)50%, and more, in cities)– Water runoff / heat absorption

• Climate change = more frequent and more intense rain showersmore intense rain showers

• Less greenspace = less habitat for native • Less greenspace = less habitat for native species

Main questionsMain questions

• Quantity and Quality of ecosystem services

• Research (regulating & cultural services)• Research (regulating & cultural services)1. Storm water retention2. Habitat provision, biodiversity, conservation3. Aesthetic benefits4. Historical uses, services, meanings5. Attitudes and decision makingg

WOWWOWWOW

WOW so what do youWOW ...so, what do youthink about all of this then? Good idea, lets plan and build!!

1a Green roofs: Stormwater1a. Green roofs: StormwaterRunoff strongly determined by;• Runoff = strongly determined by;– Substrate type & depth– Storm intensityy– Vegetation type– Roof slope

Geographic location and season– Geographic location and season

• Green roofs can;Green roofs can;– Delay initial time of runoff– Reduce total runoff

Sl l– Slow release

– ...reduce heat island effect...reduce heat island effect

Mentens et al. 2007. Landscape and Urban Planning

1b Green roofs: Stormwater1b. Green roofs: StormwaterResearch questions• Research questions– Existing green roofs (Extensive vs. Intensive)– New green roofs (Private and Public buildings)

• Various substrate types/depths, vegetation types (meadows or Sedum), roof slope

– Measure precipitationMeasure stormwater retention– Measure stormwater retention

– Measure runoff quality– Model volume of water entering the system

• BenefitsDietz 2007. Water Air Soil Pollut.

Benefits– Relief pressure on existing stormwater infrastructure– Filtering of pollution– Evapotranspiration – urban heat-isand effect

http://szurbanplanning.files.wordpress.com/2009/04/newyork_roof_gardens.jpg

2a Green roofs: Habitat2a. Green roofs: HabitatV t ti• Vegetation– Extensive roofs - studies primarily on Sedum

l f l t (d ht i t t) d th leaf succulents (drought resistant) and other xerophytic plants

• Limited biodiversity value• Limited biodiversity value– Intensive roofs - medium depth is important –

meadow vegetationmeadow vegetation• Biodiversity value can be high

– Low temperatures & drought• Substrate depth (type?) is important

– Light weight/well-drained/holding capacity/durable

http://greenerbuilds.files.wordpress.com/2009/05/sdc10586.jpg

2b Green roofs: Habitat2b. Green roofs: Habitat

• Biodiversity– Springtails... Green roofs enhance biodiversity g

but do not replace nature– Few studies on spiders, beetles, grasshoppers, p g pp

mites, orchids, birds (sometimes rare species are found on green roofs!)

– Great opportunity to survey plant and invertebrate biodiversity on historical and invertebrate biodiversity on historical and modern green roofs!

http://www.smithwick.org/steves/greenroof.jpg

2c Green roofs: Habitat2c. Green roofs: Habitat• Research questions• Research questions

– Compensatory habitat for declining species (e.g., biodiversity)– ...for maintaining desired services (e.g., pollination)

• Design– Observational

• Find existing green roofs inventory vegetation and invertebrates• Find existing green roofs – inventory vegetation and invertebrates• Compare with ’similar’ surrounding vegetation

– Experimental• Test different substrate types/depths and vegetation communities

( d i ?) i th i i h i t(meadow species?) in the Finnish environment• Simple/Intermediate/Complex vegetation communities (test the

biodiversity ~ ecosystem services link)• Selecting plants: aesthetic appeal/plant characteristics (longevity, disease

resistance)/s bstrate compositionresistance)/substrate composition

• BenefitsBiodiversity– Biodiversity

– Recommendations for Design (Greenroof Companies)

Kosareo & Ries 2007. Building and Environment.

Testing

Carter & Keeler 2008. Journal of Environmental Management

3a Green roofs: Aesthetics3a. Green roofs: AestheticsTop landscape or ’fifth facade’• Top landscape, or ’fifth facade’

• To improve sustainability, cities should be attractive for living and spending free time (recreation)– Expectations of aesthetics (visual appeal) should be

addressed before selection of plant community– Avoid urban sprawl & excessive travelling during

weekends/holidaysweekends/holidays

• Question: are these green roofs aesthetically pleasing? – Would knowledge on the benefits of green roofs

(stormwater, heat, biodiversity... ecosystem services) have human psychological benefits (health) as well as increasing their ’beauty’ in the eyes of the public?increasing their ’beauty’ in the eyes of the public?

– Increasing property values and hotels may have ’a room with a view’ option (Getter & Rowe 2006)

4a Green roofs: History4a. Green roofs: HistoryS hi t i l f• Survey historical green roofs– Historically these ’intensive’ green roofs consisted

of a thick soil layer with plants grass and/or trees of a thick soil layer with plants, grass, and/or trees and extra structural support was required -> now replaced by ’extensive’ lighter green roofs (Dietz 2007)

• Questions;– Reasons & Uses– Benefits– Functions– Problems & Structural solutions

http://farm1.static.flickr.com/226/480492008_5e80ea101e.jpghttp://tommyimages.com/Stock_Photos/Scandinavia/Iceland/Signs_of_Life/slides/Iceland_0474-Farmhouse.jpg

5a. Green roofs:Attitudes, Decision making

• To make green roofs part of city planning and structure, recognise attitudes and worries– Commonly cited challenges (landscape architects);Commonly cited challenges (landscape architects);

• Cost (but Life Cycle Cost Analysis = actually cheaper over long run)

• Lack of information, testing and data on performance of strategies (lack of tech info on how to build them!)strategies (lack of tech info on how to build them!)

• Time available for research• Resistance by project stakeholders, other consultants and code

officials• Building weight restrictions (extensive roofs > intensive roofs)• Lack of awareness of the possibility of green roofs (public

education)

• Calkins (2005) argue for the strong need for research demonstrating th i d f the economic and performance advantages of ecological design

5b. Green roofs:Attitudes, Decision making

• Questionnaires to evaluate architect/city planner/manufacturer/ public opinionsplanner/manufacturer/ public opinions

Ho to sol e ’mental’ obstacles• How to solve ’mental’ obstacles– ...Germany has seen a 10-15% growth per year in the green roof industry during last

10 yrs.

• Provide ecological & design solutions

• Questionnaires again (after knowledge h l t d)?has accummulated)?

5c. Green roofs:Attitudes, Decision making

• Diffusion of Innovations Theoryh h d t h t t id – ...how, why and at what rate new ideas

and technology spread through cultures (R 1962)(Rogers 1962)

M k t h ( d ti f i ti )Market share (adoption of an innovation)

Successive groups of consumers(young,wealthy,informed,opinionated -> old,poorer,sceptics)

http://en.wikipedia.org/wiki/Diffusion_of_innovations