A Guide to Retrofitting an Existing Roof to a Vegetated Green Roof

Transcription

1 A Guide to Retrofitting an Existing Roof to a Vegetated Green Roof Marc A. Loranger, P.E., LEED AP Associate Gale Associates, Inc. Richard Stewart Buildings & Grounds Facilities Manager Simmons College October 5, 2015

2 Learning Objectives: 1. The elements of a Green Roof 2. How to select Green Roof types 3. Important technical issues 4. Maintenance issues

3 Green Roofing

4 Seaport Area Boston, MA

5 Simmons College Boston, MA

6 System Build-Up Mimics Nature Vegetation Level Growing Medium Filter Sheet Drainage Layer / Moisture Retention Root Barrier Waterproofing Membrane and Deck

7 Types of Green Roofs Vegetation Growing Medium Filter Sheet Moisture Layer Drainage Layer Waterproofing Membrane

8 Extensive: Sedums

9 Extensive Green Roof Park-Like regular Maintenance Gardens and Parks Pitched Sedum periodic Ornamental Sedum Moss-Sedum Green Roofs Not-so Parklike low light Weight heavy Sedum Carpet

10 Intensive Green Roofs regular Maintenance Intensive Gardens and Parks Recreational Park Green Roofs Roof Garden periodic low Moss-Sedum Green Roofs Perennial Garden light Weight heavy

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12 Intensive?

13 Why Green Roofs?

14 Temperature F Rooftop Temperature Analysis 176 Bare Roof Below Vegetated Roof Cover Jun 13-Jun 17-Jun 21-Jun Time Source: Roofscapes

15 Roof Durability: Up to Triple Service Life

16 Energy Efficiency and Heat Reduction

17 Urban heat island reduction (study found 6% green roof coverage in Toronto would lower temperature by 1-2 C)

18 Stormwater Run-Off Impact Runoff from Vegetated Roof Covers (Depth: 3-14 inches) Precipitation Bare roof Vegetated Roof Covers Oct 95 Jan 96 Apr 96 Jul 96 Oct 96 Jan 97 Apr 97 Jul 97 Source: Roofscapes

19 Green Roofing Benefits

20 Economic Advantages of Green Roofing Greater energy efficiency Minimizes stormwater requirements Protects waterproofing membrane Lower life cycle costs

21 Environmental Advantages of Green Roofing Create bio-diversity Temperature regulation Improve air quality Storm water Management

22 Community and Social Benefits of Green Roofing Aesthetics Recreation Potential Noise Reduction Public Education Urban Agriculture Therapeutic Stress Reduction

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24 Waterproofing Systems

25 Built-Up Systems Coal tar pitch Asphalts Common Modified Bitumen

26 Single-ply modified bitumen

27 Torch-applied modified bitumen

28 Fluid-Applied Systems Rubberized asphalts Coldapplied asphalts Urethanes, PMMA

29 Adhered hot-applied rubberized asphalt

30 Cold-Applied Urethanes

31 Single-Ply Membranes Thermoplastic Thermoset

32 Loose-laid, single-ply thermoplastic membrane

33 Membrane Requirements

34 1. Must provide ability to prevent water from entering the building over occupied space

35 2. Membrane must facilitate run-off and withstand hydrostatic pressure

36 3. Even minor defects in membrane can be catastrophic if subjected to ponding water

37 4. Minimum 2% slope strongly recommended

38 5. Membrane must resist fertilizers, roots, and mechanical damage

39 Vegetation Grown Medium Drainage Composite Waterproofing Membrane Separation Layer Insulation Thermal Barrier (as required) Metal Deck Waterproofing Design Options Steel Deck

40 Vegetation Grown Medium Filter Fabric Insulation Drainage Composite Waterproofing Membrane Concrete Deck Intensive Green Roof PMA Design Waterproofing Design Options Concrete Deck

41 How Does it Work?

42 Water Storage...

43 ... Drainage

44 ... Aeration

45 ... Water Supply

46 ... Water Supply

47 Components of Green Roofing

48

49 Green Roof Trays and Modules More expensive than built in place Provide less design flexibility Less healthy for plant communities Provide less protection for waterproofing May be installed by inexperienced labor

50 Components of Green Roofing Hardscape

51 Components of Green Roofing Hardscape Soil confinement / curbs

52 Components of Green Roofing Hardscape Soil confinement / curbs Water retention layers

53 Components of Green Roofing Hardscape Vertical soil separation / curbs Water retention layers Drainage / filter methodology

54 Filter Material Geotextile fabric to prevent soil fines from migrating into drainage components Sometimes combined with water retention qualities for improved planting

55 Accessories of Green Roofing Hardscape Vertical soil separation / curbs Water retention layers Drainage / filter methodology Irrigation

56 Components of Green Roofing Hardscape Vertical soil separation / curbs Water retention layers Drainage / filter methodology Irrigation Root barrier

57 Components of Green Roofing Hardscape Vertical soil separation / curbs Water retention layers Drainage / filter methodology Irrigation Root barrier Protection board and Insulation

58 Components of Green Roofing Hardscape Vertical soil separation / curbs Water retention layers Drainage / filter methodology Irrigation Root barrier Protection board Fall protection

59 Plant Considerations

60 Plant Considerations Climate/hardy plantings/elevation Air intake locations/ allergies Planting establishment size and method Irrigation Exhaust locations plant burn Fire hazard/codes

61 Leak Testing

62 Inspection Procedure Start with substrate inspection Visual membrane inspection Visual flashing inspection Repair visual deficiencies Proceed to leak detection testing

63 Flood Testing

64 Disadvantages of Flood Testing Difficult and costly with sloped decks Not possible after overburden installed Delay in schedule if retests required Weather restraints (rain/freezing temps) Difficult to find exact defect location

65 Conductor Wire

66 Isolation Loops

67 Water conductor applied to surface to allow for ground connection (breach)

68 Small electrical impulses are directed onto the membrane. The electricity is searching for a ground connection (vector).

69 Plaza Deck Waterproofing

70 Advantages of EFVM Testing Exact pinpointing of membrane breaches Membrane defects can be repaired and retested without delay to the construction schedule EVFM can be performed during inclement weather Eliminates unnecessary removal of the overburden to locate a membrane breach Membrane performance can be monitored during its lifespan through the overburden

71 Vegetated Roofing Rule of Thumb Design Considerations

72 1. Determine major design objectives such as structural capacity, environmental considerations and aesthetics

73 Structural Requirements Check structural capacity of existing Dead load increased by 5% or more? IEBC versus IBC Adding mass to top of building can trigger seismic or lateral support system upgrades Original drawings available for review

74 2. Waterproofing adhered to concrete deck preferable

75 3. Perform controlled leak testing before and after covering membrane

76 4. Only use systems with proven track records

77 5. Show all connections, corners, and any detail with multiple components and/or trades

78 6. Consider having full-time monitoring/ inspection

79 7. Accessibility for ease and safety during installation, maintenance and visitors

80 7. Accessibility for ease and safety during installation, maintenance and visitors

81 8. Using a Life Cycle Cost Analysis might help shed some light over the long-term benefits of installing a green roof

82 Design Standards for Green Roofs Forschungsgesellschaft Landschaftsentwicklung Landschartsbau (FFL) Guidelines Green Roofs for Healthy Cities (GRHC) FM Approvals Approval Standards for Vegetative Roof Systems FM Global Property Loss Prevention Data Sheet 1-35 ANSI/SPRI RP-14 Whole Building Design Guide, Section Vegetated Roof Coverings Denver, CO: The Urban Drainage and Flood Control District T-04 U.S. EPA

83 ASTM Standards for Green Roofs E 2396: Saturated Water Permeability of Granular Drainage Media E2397: Determination of Dead Loads and Live Loads E 2398: Water Capture and Media Retention of Geocomposite Drain Layers E2399: Maximum Media Density for Dead Load Analysis E2400: Selection, Installation and Maintenance of Plants WK7319: Use of Expanded Shale, Clay or Slate (ESCS) as a Mineral Component in Growing Media WK575: Practice for Assessment

84 Warrantees Beware Of: Exclusions for ponding water Tray manufacturers who warrant the tray only and not the media and vegetation for 20 years Off-the-shelf growth media supplied by roofing manufacturers Note: All warrantees require maintenance programs and a FULL SYSTEM WARRANTY that includes membrane and overburden, including plants

85 Maintenance: Key to Meeting Client Expectations Should Be a Minimum of Three Maintenance Visits Per Year During Two-Year Establishment Period have this ahead of them for the weekend

86 What Tasks Should Be Executed During Maintenance Visits Remove invasive species Inspect roof drainage Spread cuttings and new plants to fill bare areas Add nutrients (as needed) Inspect penetrations/roof edges Soil analysis (yearly) Clean biomass from roof Mow roof if extensive (yearly) Dead-head Written / photo documentation

87 Common Problems Unmaintained for extended period of time leading to undesirable plants taking over and chocking out desired plantings Improperly Maintained Poor drainage Full sun plants planted in shady areas Wind scour Trampling of plants by other trades Poor design Other Trades on Green Roof

88 Case Study SIMMONS SCHOOL OF MANAGEMENT

89 Simmons College Green Roof is a 4,000 square feet roof terrace: 2,000 square feet of paved patio space 2,000 square feet of semiintensive green roof (4-8 deep) Plantings include a variety of: Drought tolerant sedum and succulents Flowering perennials and grasses

90 Simmons College Green Roof Section Concrete composite deck Tapered insulation and gypsum cover board Fully adhered PVC waterproof membrane with EFVM Drainage composite/filter fabric Gravel drainage layer Growth media Plantings Patio Section Concrete paver/pedestal system Membrane and drainage composite/filter fabric only

91 Simmons College School of Management Case Study

95 Semi-Annual Maintenance Weeding, deadhead flowering plants Watering as needed Evaluate plant health & supplement plantings Inspect roof drains and flashing Apply fertilizer and preemergent as needed

97 Economic Benefits Provides membrane protection: Solar/UV Protection for membrane longevity Mechanical Damage (foot traffic and maintenance activities) Extreme Weather Usable event space provides additional revenue for Simmons Energy savings

98 Social and Community Benefits Open to Faculty, Staff, and Students Available for private functions Integrated into Science curriculum

99 Environmental Benefits Demonstrates commitment to sustainability Contributed to LEED Gold rating Increases roof R-value (at planted areas) Bio-diversity (bees, grasshoppers, birds)

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