Living Roofs & Walls: Air Quality, Climate and Health & Wellbeing


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Presentation on the air quality, climate, and health and wellbeing ecosystem services afforded by living roofs and walls, presented at the Scottish Green Roof Forum (SGRF) inaugural conference - Edinburgh, March 2011.

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Living Roofs & Walls: Air Quality, Climate and Health & Wellbeing

  1. 1. Living Roofs & Walls: benefits to Air Quality, Climate, and Health & Wellbeing Lynette Robertson OPENspace Research Centre for Inclusive Access to the Outdoors Edinburgh College of Art & Heriot-Watt University
  2. 2. Outline • Air Quality • Climate – Global: greenhouse gas uptake (Mitigative measure) – Urban micro-climate: reduced Urban Heat Island (UHI) effect (Adaptive measure) • Health & wellbeing • Summary and conclusions • Topics for research
  3. 3. Air Quality Filtrexx Green Loxx Living Walls , Denbow Planet Friendly Solutions, Canada
  4. 4. Air Quality & Health • Lung diseases • Exacerbates respiratory illnesses • Increased incidence of cardiovascular disease • DEFRA ‘Air Pollution: Action in a Changing Climate’ Report (2010): – Average reduction in life expectancy in the UK = 6 months, annual cost £15 billion (economic cost of physical inactivity and obesity in urban areas estimated to be in excess £10 billion) – The reduction in life expectancy due to air pollution has decreased with improvements in air quality, but further benefits are increasingly costly to achieve [abatement technology] • Institute of Occupational Medicine: – “gains in life expectancy from eliminating man made fine particles are larger than those possible from eliminating motor vehicle traffic accidents or second hand cigarette smoke”
  5. 5. Main Pollutants • Particulate Matter – Type: • Solid • Liquid (secondary pollutants) – Size: • PM10 – 10 micrometres (µm) and less • PM2.5 – 2.5 µm and less • Gases – – – – NOx – Nitrogen Oxide (NO) + Nitrogen Dioxide (NO2) VOCs – Volatile Organic Compounds O3 – Ozone (secondary pollutant) SO2 – Sulphur Dioxide
  6. 6. Urban Air Quality in Scotland Particulate Matter PM10 Source: Key Scottish Environment Statistics 2010 (
  7. 7. Urban Air Quality in Scotland Nitrogen Dioxide (NO2) Source: Key Scottish Environment Statistics 2010 (
  8. 8. Air Quality in Scotland Ground level ozone (O3) Source: Key Scottish Environment Statistics 2010 (
  9. 9. PM2.5 **No safe limit** Red blood cells – approx 8 µm diameter
  10. 10. Air Pollutant Removal Mechanisms ba • Dry Deposition – transfer of gases and particles to the Earth’s surface due to turbulent air motion • Wet Deposition
  11. 11. Dry Deposition 1. Interception - Trapping - Surface reaction by plants and the growing medium (soil or substrate) 2. Stomatal uptake
  12. 12. Secondary Pollutant Formation (Indirect Effect) Transpiration + shade = lower surface temperatures
  13. 13. Green Roofs & Air Quality • 1 m2 uncut grass roof can remove up to 2 kg of air borne particulates per year (Johnson & Newton, 1996) • Intensive roofs offer greatest benefits • Species type is crucial – Size – Leaf structure -> surface area – Phytoremediation properies House with turf roof, Old Quarter, Tórshavn
  14. 14. Living Roofs & Walls: Modelling Studies • Chicago – Green Roofs, dry deposition model (Yang et al, 2008) – 20 ha of green roofs removed 1675kg of air pollutants in one year – Mostly O3 (52%), but also significant reductions in NO2 (27%), PM10 (14%) and SO2 (7%) Chicago City Hall
  15. 15. Living Roofs & Walls: Modelling Studies • Toronto – Roofs & Walls, UFORE model (Bass & Currie, 2008) – Modelled concentrations of various pollutants (PM10 , NO2 , O3 , SO2 , CO), and the economic value of removal – Greatest removal by intensive roofs but extensive roofs can aid trees and shrubs in pollution mitigation – A 10-20% increase in green roof surface area in the city centre would contribute significantly to the social, financial and environmental health of citizens
  16. 16. Living Roofs & Walls: Scotland • Improvements in AQ are increasingly costly to achieve through technological means • No safe limit for PM2.5 • 1 m2 grass roof can remove up to 2 kg / year House near Scoraig, Highlands Smailholm Tower, Borders
  17. 17. Urban Green Space & Air Quality: Possible Issues ba • Bioaerosol – – – – Pollen Spores Mites etc • Volatile Organic Compounds (VOC’s) -> O3 formation  *Select species carefully* (low isoprene and monoterpene emitters)
  18. 18. Species Selection • Environmental Toxicity – Air quality e.g. roadside – Accummulation of pollutants in the soil/ growing medium
  19. 19. Climate Global Urban micro-climate  Urban Heat Island
  20. 20. Climate Change Mitigation Uptake / absorption of greenhouse gases Carbon Dioxide Ozone Black Carbon (Particulate Matter)
  21. 21. Green Roofs & Carbon Sequestration Carbon Sequestration Potential of Extensive Green Roofs – Michigan & Maryland, USA (Getter et al, 2008) • • • • • • • Figure from Bauder’s ‘The benefits of a green roof system’ • 12 extensive roofs over 2 years Mostly Sedum Mean plant biomass: 162 g C m-2 Mean below ground biomass: 107 g C m-2 Substrate: 100 g C m-2 Sequestration varied with species Embodied energy = 6.5 kg C m-2 -> 9 years pay-back BUT: Sedum is a ‘CAM’ photosynthesiser -> C assimilation rates are only 1/2 or 1/3 that of non-CAM species
  22. 22. Green Roofs & Ozone • Greenhouse gas (direct warming effect) • Reduced CO2 absorption (indirect warming effect) • O3 is absorbed and destroyed by reacting with the plant tissue
  23. 23. Climate Change Adaptation Reduced Urban Heat Island (UHI) (or albedo) effect • Increasing green space shifts the urban environment back towards functioning more like a natural ecosystem 1. Cooling: higher albedo, evaporation, transpiration 2. Increased water storage -> further cooling
  24. 24. Urban Heat Island & Scotland Do we need to be concerned? St. Andrews UHI experiment, January 11, 2008
  25. 25. Climate Change in Scotland UKCIP projections (UKCP09): Change in mean summer temperature, medium emissions scenario - 50% probability
  26. 26. Urban Heat Island & Scotland Do we need to be concerned? YES, to some degree, because of the warming climate • Heat-wave events - likely to be an increase in frequency in the UK and across Europe • Air Quality - higher temperatures generally enhance ozone production -> greater likelihood of photochemical pollution episodes/‘smogs’ (Fowler et al, 2008) • Sustainability/Energy Conservation increased need for air conditioning in summer
  27. 27. Living Roofs and Walls & the Urban Heat Island Temperature decrease in an urban canyon due to walls and green roofs in diverse climates (Alexandri & Jones, 2008) • 7 cities: Athens, Beijing, Hong Kong, Brasilia, Montreal, Mumbi, Riyadh • Magnitude of decrease depends on climate and amount of vegetation, and in hot climates urban geometry to a lesser extent • Greatest effect of vegetation on urban temperatures found for hotter, drier climates, but humid climates also benefit • Ait temp decrease at roof level: max = 26°C, day-time mean = 12.8°C (Riyadh)
  28. 28. Living Roofs and Walls & Climate Change: Possible Issues • Impact on GHG budget – Nitrous Oxide (N2O) - fertiliser type – Ozone – VOC emissions from plants; impact on C-Seq -> **Species Type** • Embodied energy of roof/wall Life cycle cost-benefit analysis • Irrigation • Fertiliser • Resilience of plants to a warmer, wetter, more variable and more extreme climate -> droughts -> downpours -> storms
  29. 29. Climate & Species Selection Scara Brae sedum roof, Orkney (photo by Redman & Sutherland Architects, Shetland) Keep it simple & stick with nature?
  30. 30. Health & Wellbeing Unknown Illustration, Yuko Shimizu
  31. 31. Green Spaces and Health & Wellbeing Cognition Emotion/ mood Heart rate, blood pressure, etc... Psychological /mental Health Physical Health Wellbeing (Happy? Satisfied? ‘Flourishing’?) Musculoskeletal system
  32. 32. Green Spaces and Health & Wellbeing Ward Thompson & Travlou (2007) Ward Thompson, Aspinall & Bell (2010)
  33. 33. Green Spaces and Health & Wellbeing CABE ‘Community Green’ report (Ward Thompson et al, 2010) • Focused on social inequality and quality of green spaces • “Urban green space represents an important & cost effective opportunity for people to transform their local neighbourhoods and improve quality of life” Summary and full report freely available online at:
  34. 34. Living Roofs & Walls and Health & Wellbeing • Main, sometimes only, means of expanding urban green space in high density urban areas • Natural England recommendation: town and city dwellers should have access to a natural green space within 300m of home
  35. 35. Edinburgh City Centre
  36. 36. Glasgow City Centre
  37. 37. Living Roofs and Health & Wellbeing Wellbeing & productivity in the workplace - Angela Loder PhD research (University of Toronto) • Three case studies: Chicago, Toronto, London • Qualitative interviews and quantitative surveys of office worker’s perceptions of green roofs • Most workers who overlook green roofs from their workplace felt the sight of greenery amid concrete and glass gave them a ‘calming’ and ‘peaceful’ mental break from the work day, and helped workers gain perspective and clarity • This was particularly the case if the green roof was accessible
  38. 38. Living Roofs and Health & Wellbeing Greenspace and psychological health benefits (Fuller et al, 2007) • Sheffield green spaces • Psychological benefits increase with species richness of plants, and to a lesser extent birds
  39. 39. Living Roofs and Health & Wellbeing Nursing Home (US Veteran’s Administration), Washington
  40. 40. Maggie’s Cancer Care Centre Dundee
  41. 41. Summary & Conclusions • Air Quality • Climate Change • Health & Wellbeing • Intensive roofs offer most benefits, but extensive roofs are still good • Species selection is crucial in order to maximise environmental benefits and avoid wasting money • Research is needed – Particulates, NO2 and O3 – Roadsides, LAQM zones – Possible Issues: Bioaerosol, O3 (VOC’s) – Mitigation: CO2 and O3 absorption – Adaptation: reduced UHI effect – Possible issues: Increased GHG budget (festiliser -> N2O); Natural VOC emissions (-> O3); embodied energy of roof – Inner city dwellers – Office workers
  42. 42. Topics for Research • Air quality – Species selection: VOC’s, bioaerosol – Impact of increased coverage on health (should incorporate H&WB benefits) • Climate Change – Species selection: maximising mitigation (CO2, N2O, O3); resilience to current and changing climate – Embodied energy: life cycle costbenefit analysis • Plant microbial fuel cells (PMFCs) -> electricity generation • Reflective roofs • Health & wellbeing – Opportunities for research into psychological and physical mechanisms Caixa Forum, Madrid (Patrick Blanc)