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

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

Air Quality

Filtrexx Green Loxx Living Walls , Denbow Planet Friendly

Solutions, Canada

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”

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

Urban Air Quality in Scotland

Particulate Matter PM10

Source: Key Scottish Environment Statistics 2010

(www.scotland.gov.uk/Publications/2010/09/08094058/0)

Urban Air Quality in Scotland

Nitrogen Dioxide (NO2)

Source: Key Scottish Environment Statistics 2010

(www.scotland.gov.uk/Publications/2010/09/08094058/0)

Air Quality in Scotland

Ground level ozone (O3)

Source: Key Scottish Environment Statistics 2010

(www.scotland.gov.uk/Publications/2010/09/08094058/0)

PM2.5

**No safe limit**

Red blood cells – approx

8 µm diameter

Air Pollutant Removal Mechanisms ba

• Dry Deposition – transfer of gases and particles to the Earth’s surface due to turbulent air motion

• Wet Deposition

Dry Deposition

1. Interception

- Trapping

- Surface reaction

by

plants and the growing medium (soil or substrate)

2. Stomatal

uptake

Secondary Pollutant Formation (Indirect Effect) Transpiration + shade = lower surface temperatures

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

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

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

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

Smailholm Tower, Borders

House near Scoraig, Highlands

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)

Species Selection

• Environmental Toxicity

– Air quality e.g. roadside

– Accummulation of pollutants in the soil/ growing medium

Climate

Global Urban micro-climate

Urban Heat Island

Climate Change Mitigation

Uptake / absorption of greenhouse gases

Carbon Dioxide Ozone

Black Carbon (Particulate Matter)

Green Roofs & Carbon Sequestration

Carbon Sequestration Potential of Extensive Green Roofs – Michigan

& Maryland, USA (Getter et al, 2008)

• 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

Figure from Bauder’s ‘The benefits of a green

roof system’

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

Climate Change Adaptation

• 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

Reduced Urban Heat Island (UHI) (or albedo) effect

Urban Heat Island & Scotland

Do we need to be concerned?

St. Andrews UHI experiment, January 11, 2008

Climate Change in Scotland

UKCIP projections (UKCP09): Change in mean summer temperature, medium emissions scenario - 50% probability

Urban Heat Island & Scotland

• 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

Do we need to be concerned?

YES, to some degree, because of the warming climate

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)

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

Climate & Species Selection

Scara Brae sedum roof, Orkney

(photo by Redman & Sutherland Architects, Shetland)

Keep it simple & stick with nature?

Health & Wellbeing

Unknown Illustration, Yuko Shimizu

Green Spaces and Health & Wellbeing

Wellbeing (Happy?

Satisfied? ‘Flourishing’?)

Physical Health

Psychological/mental Health

Cognition

Emotion/mood

Heart rate, blood pressure,

etc...

Musculo-skeletal system

Green Spaces and Health & Wellbeing

Ward Thompson, Aspinall & Bell (2010)

Ward Thompson & Travlou (2007)

Green Spaces and Health & Wellbeing

Summary and full report freely available online at:

http://webarchive.nationalarchives.gov.uk/20110118095356/http:/www.cabe.org.uk/publications/community-green

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”

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

Edinburgh City Centre

Glasgow City Centre

Living Roofs and Health & Wellbeing

• 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

Wellbeing & productivity in the workplace - Angela Loder PhD

research (University of Toronto)

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

Living Roofs and Health & Wellbeing

Nursing Home (US Veteran’s Administration), Washington

Maggie’s Cancer Care Centre Dundee

Summary & Conclusions

• Air Quality – Particulates, NO2 and O3 – Roadsides, LAQM zones – Possible Issues: Bioaerosol, O3 (VOC’s)

• Climate Change – Mitigation: CO2 and O3 absorption – Adaptation: reduced UHI effect – Possible issues: Increased GHG budget (festiliser -> N2O); Natural VOC

emissions (-> O3); embodied energy of roof

• Health & Wellbeing – Inner city dwellers – Office workers

• 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

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 cost-benefit 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)