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Green roofs
- 1. WELCOME 1
- 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 6
- 7. Types of green roofs 7 Intensive ExtensiveSemi-intensive
- 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 10
- 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
- 12. Anatomy of a green roof 12
- 13. Waterproofing membrane • Protects the roof from leakage • Example: – Ethylene propylene diene monomer (EPDM) membrane – Butyl rubber membrane 13
- 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 16
- 17. Separation/filter layer • Resists clogging from fine soil particles • Prevents clogging of the drainage layer • Made up of geotextile such as fleece 17
- 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. 18
- 19. Vegetation • Dictated by the depth of substrate • Thin green roofs: sedum and herbs • Thick green roofs: wide range 19
- 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 20
- 21. Trees 21 Acacia dealbata Koelreuteria panniculata Ficus benjamina Araucaria cookii
- 22. Conifers 22 Cupressus sp Juniperus sp Pinus sp
- 23. Small shrubs 23 Lavandula sp Nandina domestica Punica nana
- 24. Medium large shrubs 24 Callistemon citrinus Elaeagnu sangustifolia Vitexagnus castus Abelia grandiflora
- 25. Climbers 25 Jasminum officinale Passiflora caerulea Solanum crispum
- 26. Herbaceous perennials 26 Tropaeolum majus Tithonia rotundifoliaPortulaca grandiflora Verbena
- 27. Annuals 27 Eschscholzia californica Amaranthus Argyranthemum Ipomoea purpurea
- 28. Plants for hanging basket 28 Bidens pilosa Brachycome Daisy Felicia
- 29. Succulents 29 Aeonium sp Aloe vera Sedum sp
- 30. Grasses 30 Briza media Panicum virgatum Pennisetum alopecuroides Pennisetum rubrum
- 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
- 36. Benefits of green roof 36
- 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
- 39. 39 Temperature variation of bare and green roofs (Qin et al., 2012) Temperature(oC)
- 40. 0 5 10 15 20 25 30 35 40 45 Temperature(oC) Time Outside air temperature Room temperature with bare RCC slab Room temperature with a green roof Comparison of temperature in rooms with and without green roofs 40 (Pandey et al., 2013)
- 41. Urban heat island effect 41 Lateafternoontemperature
- 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 51
- 52. Aesthetic improvement in buildings 52
- 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
- 56. Thank you 56