Green roofs in urban areas - University of Helsinki
Green roofs in urban areas Urban Ecology Research Group, Botanic Garden University of Helsinki
Background – to recap!• 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) – Thermal benefits to the surroundings (microclimate, urban heat island effect) – CO2 sequestration – Habitat provision (’recover greenspace’) – Dust/pollution filtering – Gardening/food production – Increase longevity of roofing membranes – Recreation, Education – Aesthetics A th ti – Noise reduction – Business opportunities (nurseries, contractors, industry) Hobbiton, Middle-Earth (http://www.the-shire.eu/Hobbiton.jpg)
Examples pSod/turf roofs from Scandinavia Chicago City Hall, USA ACROS F k k B ildi Fukouka Building, J Japan Singapore Residential application All pics from: http://egardens.blogspot.com/2009/03/green-roofs-more.html
Scientific 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 = 15 – Cost/benefit, design, policy = 15 – Substrate depth, type = 14 – Biodiversity = 3 – Pollution = 3 – Ecosystem services = 2 Sound = 2 20 – 15 Countries Number of studies• – Germany, USA, Canada 10 – ...closer to home: Sweden • Stormwater, Stormwater vegetation (Sedum moss), substrate N P (Sedum-moss) substrate, N, 5 0 1996 1998 2000 2002 2004 2006 2008 2010 Year
Main types of Green roofs (Europe) • E t Extensive i – Substrate layer max of 150 mm – Sedum species – Can be on sloped roofs (up to 45o) • Intensive – Substrate layer more than 150 mm – Grasses, perennial herbs, shrubs – Slope less than 10o – Can be used as roof gardens
Intensive roofs Extensive roofsOberndorfer et al. 2007. BioScience
The problem problem...• I t Intense urbanisation + iinfilling = hi h % b i ti filli higher impermeable surfaces per area (up to 50%, 50% and more in cities) more, – Water runoff / heat absorption• Climate change = more frequent and more intense rain showers• Less greenspace = less habitat for native species
Main questions• Quantity and Quality of ecosystem services• Research (regulating & cultural services) 1. Storm water retention 2. Habitat provision, biodiversity, conservation 3. Aesthetic benefits 4. Historical uses, services, meanings 5. Attitudes and decision making g
WOW WOW WOW ...so, what do you so think about all of this then? Good idea, lets plan and build!!
1a. 1a Green roofs: Stormwater• Runoff = strongly determined by; – Substrate type & depth – Storm intensity y – Vegetation type – Roof slope – Geographic location and season• Green roofs can; – Delay initial time of runoff – Reduce total runoff – Sl Slow release l – ...reduce heat island effect Mentens et al. 2007. Landscape and Urban Planning
1b. 1b Green roofs: Stormwater• 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 precipitation – Measure stormwater retention – Measure runoff quality – Model volume of water entering the system Dietz 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. 2a Green roofs: Habitat• V Vegetation t ti – Extensive roofs - studies primarily on Sedum lleaf succulents (d f l t (drought resistant) and other ht i t t) d th xerophytic plants • Limited biodiversity value – Intensive roofs - medium depth is important – meadow 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. 2b Green roofs: Habitat• Biodiversity – Springtails... Green roofs enhance biodiversity g but do not replace nature – Few studies on spiders, beetles, g p grasshoppers, pp mites, orchids, birds (sometimes rare species are found on green roofs!) – Great opportunity to survey plant and invertebrate biodiversity on historical and modern green roofs! http://www.smithwick.org/steves/greenroof.jpg
2c. 2c Green roofs: Habitat• 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 • Compare with ’similar’ surrounding vegetation – Experimental • Test different substrate types/depths and vegetation communities (meadow species?) iin th Finnish environment ( d i ?) the i i h i t • Simple/Intermediate/Complex vegetation communities (test the biodiversity ~ ecosystem services link) • Selecting plants: aesthetic appeal/plant characteristics (longevity, disease resistance)/substrate resistance)/s bstrate composition• Benefits – Biodiversity – Recommendations for Design (Greenroof Companies) Kosareo & Ries 2007. Building and Environment.
TestingCarter & Keeler 2008. Journal of Environmental Management
3a. 3a Green roofs: Aesthetics• Top landscape, or ’fifth facade’ landscape• 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/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 property values and hotels may have ’a room with a view’ option (Getter & Rowe 2006)
4a. 4a Green roofs: History• S Survey hi t i l green roofs historical f – Historically these ’intensive’ green roofs consisted of a thick soil layer with plants, grass and/or trees plants grass, 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.jpg http://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); • 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!) • 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 the th economic and performance i d f advantages of ecological design
5b. Green roofs: Attitudes, Decision making• Questionnaires to evaluate architect/city planner/manufacturer/ public opinions• Ho to sol e ’mental’ obstacles How solve – ...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 has h accummulated)? l t d)?
5c. Green roofs: Attitudes, Decision making • Diffusion of Innovations Theory – ...how, why and at what rate new ideas h h d t h t t id and technology spread through cultures (Rogers 1962) (R Market h M k t share (adoption of an innovation) ( d ti f i ti ) Successive groups of consumers (young,wealthy,informed,opinionated -> old,poorer,sceptics)http://en.wikipedia.org/wiki/Diffusion_of_innovations