roof covered with vegetation either completely or partially. Three types of green roof: extensive (shallow), semi intensive (moderate) and intensive (deep) green roofs. History traces back to the Hanging gardens of Babylon. Germany is the birthplace of modern day green roofs. a green roof has seven different layers: waterproofing membrane, root barrier mambrane, protection layer,drainage layer,filter layer, media and the vegetation/plant layer. advantages include reduce energy consumption and urban heat island effect, air pollution, storm water mitigation, noise reduction and aesthetic beauty.
2. • Percentage of urban population is increasing
• Development often made at the expense of green areas
• Increase in area of impermeable spaces
• Numerous consequences
• Ecosystem restoration - need of the hour
2
Introduction
3. Green roofing – a tool for
ecological engineering
Andrew L Myrthong
2014-12-126
Dept. of Pomology and
Floriculture
3
4. Outline
1. Green roof definition
2. History of green roof
3. Types of green roof
4. Quality of the roof structure
5. Anatomy of green roof
6. Plants for green roof
7. Installing a green roof
8. Benefits of green roof
9. Summary
10. Conclusion
4
5. Green roofs
• Roof covered with vegetation and growing medium
• Eco roof/living roof/vegetated roof
• Converts dead space to dynamic space
• Helps to break the monotony
• Reduces negative impact of buildings on local environment
5
6. History
• Hanging gardens of Babylon
• European houses were covered
with sod and turf
• Germany is the birthplace of
modern day green roof
(Magill et al., 2011)
• Authorities encouraged such green
roofs
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8. Intensive green roof
• Depth 10 inches and more
• Supports trees and shrubs
• Initial investment is high
• Heavier than both the types
• Requires more maintenance
8
9. Semi-intensive green roof
• Intermediate type
• Depth ranges from 6 to 10
inches
• Grasses, herbaceous
perennials and shrubs
• Requires more maintenance
• Higher initial cost
9
10. Extensive green roof
• Depth ranges from 3 to 6
inches
• Succulents, herbs and grasses
• Low establishment cost
• Light in weight
• Not accessible
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11. Quality of the roof structure
• Made of wood, steel or
concrete
• Support 25 to 100 pounds per
square foot
• Existing roofs require structural
reinforcing
11
14. Root barrier membrane
• Protects the waterproofing
membrane
• Thickness at least 2.5 mm
• Example:
– High density polyethylene
(HDPE)
– High density polypropylene
14
15. Tough protection mat
• Protects the inner membranes
• Protection mats weigh 500 to 900
g/m2
• Water and nutrient reservoirs
• Recycled non-rotting
polypropylene or polyester
15
16. Drainage layer
• Stores water in green roofs
• Helps plant survive dry weather
• Example:
– Gravel
– Dimpled plastic sheets
– Ribbed fabric laminates
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17. Separation/filter layer
• Resists clogging from fine soil
particles
• Prevents clogging of the
drainage layer
• Made up of geotextile such as
fleece
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18. Soil
• Not an ordinary soil
• Optimum water retention capacity
• Light in weight
• pH: 6.5 to 8.0
• Lava, pumice, expanded clay,
Rockwool etc.
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19. Vegetation
• Dictated by the depth of substrate
• Thin green roofs: sedum and
herbs
• Thick green roofs: wide range
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20. Plants for green roof
• Right plant for the right place
• Succulents are the backbone of green roofs
• Herbaceous perennials used as accents
• Turf, shrubs, trees in intensive green roof
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32. Load bearing capacity
• Dictates the type of green roof possible
• Dead loads and live loads
• Intended function, extent of landscaping, anticipated
traffic
• Review by a structural engineer
• Intensive: 200 to 1000 kg/m2
• Extensive: 50 to 200 kg/m2
32
33. Integrity test
• Checks the integrity of the roof membrane
• Flooding test
• Infrared [IR] moisture survey
• Electric Gradient Leak Location [EGLL]
• Leak Locate Grid System [LLGS]
33
34. Site considerations
• Inspect drainage locations
• If accessible, incorporate safety measures
• Observe areas with sun/shade exposure
• Check the wind velocity
• Choose appropriate flora
34
35. 35
Installing different layers
Root barrier
Drainage layer and
filter fabric
Soil and plants
Water proofing
membrane
Tough protecting
mat
Drain
boxes and
channels
38. Reduced energy use
• Reduces heat flux via evapotranspiration
• Acts as an insulator
• Minimizes the use of air conditioners
• Prevents heat escape in winter
38
42. Contd…
• Temperature difference between a city and the countryside
• Buildings absorb solar radiation and reflect back as heat
• Macro scale application could lead to maximum reduction of
2oC
(Smith and Roeber, 2011)
42
43. Impact of green roof on the urban heat island
effect
43
UrbanHeatisland(oC)
Local time
(Li et al., 2014)
44. Air pollution
• Plants are influential in reducing air pollution
(Currie and Bass, 2008)
• Green roof substitutes demolished vegetation
• A green roof with an area of 109.0 ha removes 7.87MT air
pollutants per year
(Van Woert et al., 2005)
44
45. Total pollutant removal by different type of
plants in a green roof
45
3.74
7.4
1.37
5.57
1.67
3.26
0.63
2.69
1.6
3.14
0.61
2.17
0
1
2
3
4
5
6
7
8
Nitrogen dioxide Ozone Sulphur dioxide Particulate
matter
Mgofpollutants
Trees Shrubs Grasses
(Currie and Bass, 2008)
46. Storm water management
• Impermeable surfaces generate storm water runoff
• Limited infiltration capacity
• Peak flow results in flooding
• Average precipitation retention is 56%
(Gregoire and clausen, 2011)
• Green roof delays peak discharge by 30 minutes to 1 hour
(Wong et al., 2014)
46
47. Comparison of percentage of rainfall
retention by standard and green roofs
47
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
standard roof green roof
Rainfallretention(%)
Roof type
average
retention
retention at
peak runoff
(DeNardo et al., 2005)
48. Comparison of surface runoff volume for
different rainfall duration
48
0
20
40
60
80
100
120
140
160
180
15 min 30 min 60 min
Surfacerunoffvolume(ml)
Rainfall duration (min.)
long grass
short grass
sedum
(Mickovski et al., 2013)
49. Sound insulation
• Noise disturbs people
• Decreases efficiency of employees
• Lowers the property value
• Green roof reduces noise through Transmission Loss (TL)
• At lower frequencies TL 5 to 13 db
• At higher frequencies TL 2 to 8 db
(Connelly and Hodgson, 2008)
49
50. Comparison of transmission loss between
conventional and green roofs
50
0
10
20
30
40
50
60
70
50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000
Transmissionloss(db)
Frequency (Hz)
Green roof Conventional
(Connelly and Hodgson, 2008)
51. Aesthetic improvement
• Effective for beautifying built
environment
• Enhances good designs
• Disguises bad designs
• Psychological effect
• Provides a visual relief
• Relaxation and restoration
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53. Green buildings in India
53
CII-Sohrabji Godrej Green Business
Centre, Hyderabad
Green Hill, ONGC campus,
Dehradun
54. Summary
• Roofs covered with vegetation
• Germany- birthplace of modern green roofs
• Intensive, semi-intensive and extensive
• It has eight functional layers
• Helps to fight against the disruption of ecosystem
54
55. Conclusion
• Ideal architectural combination of aesthetics,
economy and ecology
• Technology for mitigating environmental issues
• Research gaps in Indian context
• Supports sustainable urban planning
• Improves quality of urban life
55
