Why Consider a Green Roof?


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In this time of rising temperatures, abundant rain and socioeconomic imbalance, this seminar will suggest that green roofs are a powerful green building Best Management Practices (BMPs).

This presentation will outline the application, feasibility, benefits and challenges of green roofs in commercial application and put several widely debated questions into perspective: modular trays v. contiguous installations, upfront cost v. long-term investment, green roof v. other options, public access v. limited access, etc. Using local, national and international examples, she will explore green roof issues re: longevity, energy savings, stormwater management, maintenance, incentives and LEED points.

The three learning objectives are a) to understand green roof ROI for commercial buildings, b) to compare stormwater strategies of green roofs v underground cisterns and porous pavers and c) to compare green roofs to a solar roof or a white reflective roof.

Green roofs are a means to lowering the overall ambient temperature, reducing longterm costs on our buildings, sequestering CO2 and producing O2, improving the quality of life in our cities and boosting our green economy. Come learn more about green roofs at this seminar on May 7th.

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  • Studies show the total volume of rain water would be reduced by 54% with Bakor green roofs. The soils and our composite drainage board retains sufficient water to maintain plant life.
  • This is the most important slide. Take your time to get this message across. We have just spent a lot of time getting into the science and benefits of green roof and it may seem complicated to some. We need to bring them back to reality. A green roof is a roof to begin with and must first and foremost stop water from entering the building. This is where we are experts and have the experience. Mr.. Architect, the occupants will not likely sue you or complain if the plants die. They will however if water enters the building. Based on our experience (since 1967) 790-11 has proven that it is the best membrane for waterproofing concrete structures. It is a tried and tested product.
  • Vegetation Free Zones are area ways for drainage and moisture evaporation.
  • We start with the concrete deck.
  • Our system requires the use of 930-18 Polymer Modified Primer for better adhesion.
  • Apply two layers of 790-11EV hot applied rubberized asphalt with polyester fabric reinforcement.
  • The protection layer is typically G100 s/s base sheet, for higher warranty conditions use NP180 s/s
  • Apply a layer of rigid insulation.
  • The drainage board is key to the system, Bakor Green Roof incorporates a prefabricated free flowing drainage board with a moisture barrier and root barrier.
  • A filter fabric is applied over the drain board to catch the fine soil particles.
  • Subject to the plant material, the design of the soil is determined and placed over the fabric.
  • This is the Bakor Green Roof System.
  • Mock up of typical 2 layer system
  • Why Consider a Green Roof?

    1. 1. A Green Roof Presentation: Why Consider a Green Roof ? specially prepared by Karen L. Weber for NEXUS Green Roundtable Spring 2009
    2. 2. Best Practices/AIA <ul><li>NEXUS Green Roundtable is a Registered Provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request. </li></ul><ul><li>This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of the presentation. </li></ul>
    3. 3. Learning Objectives <ul><li>To understand green roof ROI for commercial buildings </li></ul><ul><li>To compare stormwater strategies – green roofs v underground cisterns and porous pavers </li></ul><ul><li>To compare green roofs to a solar roof or a white reflective roof </li></ul>
    4. 4. Chinatrust Bank According to Chinese belief, the roof of a building belongs to the spirit world and acts as a landing platform for spirits to descend and ascend.
    5. 5. Learning Objective #1 <ul><li>Green Roof </li></ul><ul><li>Return On Investment </li></ul>
    6. 6. On a hot summer day, temperatures on a conventional roof can soar to 150ºF to 200ºF while a green roof remains between 77ºF to 90ºF.
    7. 7. Roof Replacement <ul><li>Conventional roofs are replaced every 15-20 years. </li></ul><ul><ul><li>62% of roofs in the US have problems in the first year </li></ul></ul><ul><ul><li>99% have problems in the first 10 years </li></ul></ul><ul><ul><li>(source: National Research Council of Canada, 1997) </li></ul></ul><ul><li>Well-installed green roofs are replaced every 50-100 years or more. </li></ul><ul><ul><li>German and European experience prove this </li></ul></ul><ul><ul><ul><li>New Green Roof technology in Germany functioning > 50 yrs </li></ul></ul></ul><ul><ul><ul><li>Green Roofs in Berlin last over 90 yrs before needing attention </li></ul></ul></ul><ul><ul><ul><li>Green Roof in Zurich planted in 1914 still thriving </li></ul></ul></ul><ul><ul><li>In the US, we’ve already seen excellent results for roofs that are 12 years old. </li></ul></ul><ul><ul><li>(source: Roofscapes, Inc. Summer Assessment 2007) </li></ul></ul>
    8. 8. Moos Water Filtration Plant Zurich, Switzerland This green roof was established as an earth roof in 1914 and was colonized by 175 plants along with 9 local orchids, several of which only exist here. Very little work has been done to maintain this 350,000 sf green roof. The substrate has 5 cm of sand and gravel and 15-20 cm of topsoil.
    9. 9. Weathering <ul><li>Green Roofs allow the roof to better weather the effects of climate & UV rays: </li></ul><ul><ul><li>Protect against UV rays </li></ul></ul><ul><ul><li>Protect against wind, rain, sleet </li></ul></ul><ul><ul><li>Protect against expansion & contraction </li></ul></ul><ul><ul><li>Protect against sub-zero temperatures </li></ul></ul><ul><ul><li>Protects from temperature spikes & dips </li></ul></ul>
    10. 10. Energy Transfers SUMMER WINTER freezing
    11. 11. HVAC Longevity <ul><li>Green Roofs serve as biofilter: </li></ul><ul><ul><li>Trap large amounts of dusts and toxins. </li></ul></ul><ul><ul><li>NOx – SOx </li></ul></ul><ul><ul><li>Absorb CO 2 and Produce O 2 </li></ul></ul><ul><ul><li>(source: studies done by Michigan State) </li></ul></ul><ul><li>Reduce load on HVAC filters and overall system. </li></ul>
    12. 12. Marketing, Aesthetics, RE Value From Vancouver Convention Center to NYC Clinton Park
    13. 13. Green Roofs as Equivalent to Open Space: Jackson Square <ul><li>10-year 24-hour rainfall event </li></ul><ul><li>4 inch Type I </li></ul><ul><ul><li>C = .40 </li></ul></ul><ul><ul><li>CN = 70 </li></ul></ul><ul><li>6 inch Type III (dual media) </li></ul><ul><ul><li>C = .33 </li></ul></ul><ul><ul><li>CN = 66 </li></ul></ul><ul><li>Runoff/Rainfall = 35% (22% in summer) </li></ul><ul><ul><li>2 feet/year (15,000 gal for 1,000 sf roof area) </li></ul></ul>
    14. 14. ROI Summary <ul><li>Cooling/Reduce Use of AC </li></ul><ul><li>and Reduce Peak Demand </li></ul><ul><li>Roof Longevity </li></ul><ul><li>HVAC Longevity </li></ul><ul><li>Building Longevity </li></ul><ul><li>Reduce heating bills </li></ul><ul><li>Increase RE Value </li></ul><ul><li>Increase usable space </li></ul><ul><li>Marketing </li></ul><ul><li>STORMWATER MANAGEMENT </li></ul>Zurich Airport
    15. 15. Learning Objective #2 <ul><li>Green Roof </li></ul><ul><li>Stormwater Management Comparison </li></ul>
    16. 16. Stormwater Strategies <ul><li>Green roofs </li></ul><ul><li>Underground cisterns </li></ul><ul><li>Rainwater recovery </li></ul><ul><li>Porous pavers and rain gardens </li></ul><ul><li>What are the objectives? </li></ul>
    17. 17. Green Roofs Comprehensively Manage Stormwater <ul><li>Retention Function </li></ul><ul><li>(Permanent Storage): </li></ul><ul><ul><li>15% by volume (moisture content at 1/3 bar capillary pressure) </li></ul></ul><ul><li>Detention Function </li></ul><ul><li>(Transient Storage): </li></ul><ul><ul><li>15% - 35% by volume (Maximum Water Capacity) </li></ul></ul>A green roof demonstrates a first-order discharge rate – performing as well as a detention basin.
    18. 18. <ul><li>Stormw ater Runoff v. Retained </li></ul>Total Rain Fall and Roof Runoff in Summer 2002 (Ottawa) 0 5 1 0 15 2 0 Rain Fall Mod Bit. Green Roof Rain/Runoff ( inches ) LEGEND Total Vol. Rain Rain Water Retained Rain Water Runoff
    19. 19. Green Roofs Decrease Stormwater Runoff Rates <ul><li>Reduce stormwater runoff by about 50% over the course of the year </li></ul><ul><li>Control runoff from over 95% of storms </li></ul><ul><li>Prohibit any immediate runoff from the smallest 25% of all storms </li></ul><ul><li>Substantially reduce peak flow rates </li></ul>An extensive green roof with 4” of soil (media) can:
    20. 20. Other Stormwater Strategies <ul><li>Subsurface rainwater detention: </li></ul><ul><ul><li>$2-2.50/gallon installed </li></ul></ul><ul><li>Harvest pump </li></ul><ul><ul><li>$10,000-100,000 </li></ul></ul><ul><ul><li>Pump works </li></ul></ul><ul><ul><li>Filtration treatment </li></ul></ul><ul><ul><li>Cooling </li></ul></ul><ul><li>Porous pavers ($4-5/sf) </li></ul><ul><ul><li>Drainage layer </li></ul></ul><ul><ul><li>Piping </li></ul></ul>
    21. 21. Learning Objective #3 <ul><li>Green Roof </li></ul><ul><li>Comparison with Solar Roof, White Roof & Heliotstats </li></ul>
    22. 22. Solar Roofs
    23. 23. Energy Cooling properties of green roofs improve, while white roofs degrade over time and are affected by dust accumulation. White Reflective Roofs Skylights/Heliostats
    24. 24. Comparison of White & Green Roofs <ul><li>Green roofs cool primarily by latent heat loss and high natural albedo. </li></ul><ul><li>Green roofs reduce heat flow into the building below to levels not achievable by white roofs. </li></ul><ul><li>White roof albedo declines by .15/year but can occur in just 2 months. Brightness can be restored by regular washing at least twice per year. </li></ul><ul><li>Every 2-3 years the white roof needs resurfacing. </li></ul><ul><li>Main Source: Gaffin, et. al., Energy Balance Modeling Applied to a Comparison of White and Green Roof Cooling Efficiency . </li></ul>
    25. 25. Heliostats on Green Roof
    26. 26. Life Cycle Analysis <ul><li>Higher initial cost, however: </li></ul><ul><ul><li>Membrane will last at least 50 years – non-green roofs only 15-20 yrs </li></ul></ul><ul><ul><li>Energy savings in cooling and heating & HVAC </li></ul></ul><ul><ul><li>Stormwater savings in piping & retention </li></ul></ul><ul><li>When taking these factors into account, the savings gained by a green roof come within about 15% of the cost of a conventional roof according to Damon Farber Associates and Miller Dunwiddie Architecture of Minneapolis. </li></ul><ul><li>Short Term Owners: </li></ul><ul><ul><li>Increased cost of roof system </li></ul></ul><ul><ul><li>Will not see return on investment long-term </li></ul></ul><ul><ul><li>Will increase marketability </li></ul></ul><ul><ul><li>Points for LEED Accreditation </li></ul></ul><ul><li>Long Term Owners </li></ul><ul><ul><li>Increased life of roof membrane </li></ul></ul><ul><ul><li>Heating and cooling savings </li></ul></ul><ul><ul><li>Will see return on investment in 8-13 years </li></ul></ul><ul><ul><li>Points for LEED Accreditation </li></ul></ul>
    27. 27. Green Roof Types <ul><li>Extensive v Intensive </li></ul><ul><ul><li>Extensive: 3-5” unirrigated </li></ul></ul><ul><ul><li>Semi-intensive: 6-8” </li></ul></ul><ul><ul><li>Intensive: 9”+ </li></ul></ul><ul><li>Comparison of extensive green roof systems: containers v. integrated or contiguous systems </li></ul><ul><ul><li>Modular/containers </li></ul></ul><ul><ul><li>Pre-vegetated mats </li></ul></ul><ul><ul><li>Cuttings </li></ul></ul><ul><ul><li>plugs </li></ul></ul><ul><li>Load, Maintenance </li></ul><ul><ul><li>Index for extensive roofs: 6.75 lbs/planting inch/sf (fully saturated) </li></ul></ul><ul><ul><li>2-3 hrs/1000 sf/yr/split between spring and fall </li></ul></ul>
    28. 28. World Trade Center, West Podium Park, Boston, MA
    29. 29. Boston World Trade Center, West Podium Park, 5” extensive podium green roof
    30. 30. Integrated Green Roof Technology
    31. 31. Modular Green Roof
    32. 32. Pre-Grown Mats
    33. 33. Sedum Cuttings
    34. 34. Sedum Plugs
    35. 35. Wal-Mart Store #5402 11 months
    36. 36. Wal-Mart Store #5402 Placing Pavers & Media Installing Drainage Layer
    37. 37. Wal-Mart Store #5402 <ul><li>Distributing Sedum cuttings </li></ul>Installing hydromulch
    38. 38. Wal-Mart Store #5402 Freshly Planted
    39. 39. Largest Green Roof Monitoring Program in World at Wal-Mart
    40. 40. Installing the Green Roof on WGBH
    41. 41. Green Roof/Solar Combination: Installing Green Roof on WGBH
    42. 42. Newly Planted Solar/Green Roof WGBH Headquarters, Boston, MA
    43. 43. <ul><li>E2397 : Standard Practice for Determination of Dead Loads and Live Loads for Green Roof Systems </li></ul><ul><li>E2399 : Standard Test Method for Maximum Media Density for Dead Load Analysis of Green Roof Systems </li></ul><ul><ul><ul><li>Density </li></ul></ul></ul><ul><ul><ul><li>Maximum water retention </li></ul></ul></ul><ul><ul><ul><li>Non-capillary porosity </li></ul></ul></ul><ul><ul><ul><li>Permeability </li></ul></ul></ul><ul><li>E 2398 : Standard Test Method for Water and Media Retention of Geocomposite Drain Layers for Green Roof Systems </li></ul><ul><li>E 2396 : Standard Test Method for Saturated Water Permeability of Granular Drainage Media for Green Roof Systems </li></ul>ASTM Standards
    44. 44. LEED @ CERTIFICATION <ul><li>Site Development (p.69) Protect or restore habitat </li></ul><ul><ul><ul><li>Green Roof can contribute towards 1 point </li></ul></ul></ul><ul><li>Site Development (p.73) Maximize Open Space </li></ul><ul><ul><ul><li>Green Roof can contribute to credit compliance towards 1 pt </li></ul></ul></ul><ul><li>Stormwater Design </li></ul><ul><ul><li>Quantity Control (p. 77) – 1 point </li></ul></ul><ul><li>Stormwater Design </li></ul><ul><ul><li>Quality Control (p. 85) – 1 point </li></ul></ul><ul><li>Heat Island Effect (p.91) – Non-roof </li></ul><ul><ul><li>Consider replacing constructed surfaces with Green Roofs – 1 pt </li></ul></ul><ul><li>Heat Island Effect (p. 97) – Roof </li></ul><ul><ul><li>Install a Green Roof at least 50% of roof area – 1 point </li></ul></ul><ul><li>Building Reuse (p. 247) </li></ul><ul><ul><li>Potential role in maintaining existing roof 1-2 points </li></ul></ul><ul><li>Construction Waste Management (p.255) </li></ul><ul><ul><li>Potential role in construction waste management in diverting roofing materials from disposal 1-2 points </li></ul></ul><ul><li>Materials & Resources (p. 263) </li></ul><ul><ul><li>Green Roof could help contribute for materials reuse 1-2 points </li></ul></ul><ul><ul><li>Recycled content (p. 264) – contribution to 1-2 points </li></ul></ul><ul><li>Recycled Content (p. 269) </li></ul><ul><ul><li>Green Roof helps with 1 to 2 points </li></ul></ul><ul><li>Regional Materials (p. 276) </li></ul><ul><ul><li>Green Roofs when extracted, processed and manufactured regionally can help towards 1 to 2 points </li></ul></ul><ul><li>Rapidly Renewable Materials (p. 283) – 1 point </li></ul><ul><li>Innovation in Design (p. 395) – Green Roof 1 to 4 points </li></ul><ul><li>POSSIBLE TOTAL = 23 POINTS </li></ul>
    45. 45. Green Roof Design GREEN ROOF SYSTEMS
    46. 46. Green Roof Design GREEN ROOF SYSTEMS Vegetative Cover
    47. 47. Green Roof Design GREEN ROOF SYSTEMS Vegetative Cover Water Retention Drainage System
    48. 48. Green Roof Design GREEN ROOF SYSTEMS Vegetative Cover Water Retention Drainage System High Performance Waterproofing
    49. 49. <ul><li>Waterproofing Membrane </li></ul><ul><li>One of the most critical design elements of any Green Roof System is the Waterproofing Membrane . No matter how good it looks on top, what is below must keep the water out! </li></ul>
    50. 50. Deck Hot Applied Rubberized Waterproofing
    51. 51. Polymer Modified Primer Hot Applied Rubberized Waterproofing
    52. 52. 790-11 EV Membrane Hot Applied Rubberized Waterproofing
    53. 53. Protection Course Hot Applied Rubberized Waterproofing
    54. 54. Insulation Hot Applied Rubberized Waterproofing
    55. 55. Root Barrier/Water Retention Hot Applied Rubberized Waterproofing
    56. 56. Filter Fabric Hot Applied Rubberized Waterproofing
    57. 57. Growing Medium, Plants and Wind Erosion Layer Hot Applied Rubberized Waterproofing
    58. 58. $ 6 .00 sq/ft $ 3.00 sq/ft $ 7 - 55 sq/ft Hot Applied Rubberized Waterproofing
    59. 59. <ul><li>Base coat applied at 90 mils </li></ul>Waterproofing
    60. 60. Applying Hot Applied Rubberized Waterproofing
    61. 61. Seasonal High Water Table Bedrock Soil Horizon Vegetation Emulating Nature
    62. 62. Drain Sheets Mats
    63. 63. Dual Media
    64. 64. Mineral Drainage Layers Emulating Nature
    65. 65. Reasons to Irrigate <ul><li>Support specific plant palate </li></ul><ul><li>Optimize Evapotranspiration Losses </li></ul><ul><ul><li>Reduce Runoff </li></ul></ul><ul><ul><li>Modify Micro-Climate </li></ul></ul><ul><li>Optimize Thermal Benefit </li></ul><ul><ul><li>Evaporative Cooling (Latent heat transfer) </li></ul></ul>
    66. 66. Irrigation Methods <ul><li>Surface Systems </li></ul><ul><li>[ Required for most systems with artificial drainage layers ] </li></ul><ul><ul><li>Drip ( Media depth of 6”, or greater, recommended ) </li></ul></ul><ul><ul><li>Overhead Spray </li></ul></ul><ul><li>Base Systems </li></ul><ul><li>[Single layer systems, or systems with granular drainage layer] </li></ul><ul><ul><li>Capillary </li></ul></ul><ul><ul><li>‘ Standing Water’ Method </li></ul></ul>
    67. 67. Capillary Irrigation Method Drip Line Capillary Fabric
    68. 68. Capillary Irrigation Method
    69. 69. Base Flood Irrigation <ul><li>Water dispensed at the rate that plants require it </li></ul><ul><li>Little direct evaporation </li></ul><ul><li>No fancy sensors or controllers are required </li></ul><ul><li>Water levels are maintained by float valve </li></ul>
    70. 70. One-inch of water sustained by float valve Roots drink from the drainage zone Base Flood Irrigation Approach
    71. 71. Strategic Use of Basal Irrigation Techniques float controller boxes ponding riffles
    72. 72. ponding element bonded to protection sheet water surface separation fabric primary membrane Enhanced Water Retention Using Ponding Riffles
    73. 73. Ponding Riffles
    74. 74. Optigr ü n Trickle Irrigation Modules Trickle Irrigation Modules
    75. 75. Augmenting System Drainage
    76. 76. Internal Drainage
    77. 77. Wind-Stabilized Designs
    78. 78. Artificial Terrain Elements
    79. 79. Free-Standing Railing System <ul><li>Does not penetrate waterproofing </li></ul><ul><li>Satisfies code requirements </li></ul>
    80. 80. Unit Paver System
    81. 86. Life Expression Wellness Center – Pennsylvania
    82. 89. Intensive: Oaklyn Branch Library
    83. 91. Intensive: Oaklyn Branch Library 14” irrigated green roof assembly
    84. 93. Oaklyn Library, Evansville, IN
    85. 97. The Four Seasons Hotel, Boston, MA Roofscapes, Inc.
    86. 98. Chicago City Hall Roofscapes, Inc. Chicago saves $4000-5000 per year on the City Hall energy bill since its roof was greened.
    87. 100. Notebaert Nature Museum (6.0” thick irrigated ) Veneer Wetlands
    88. 101. Mass General Healing Garden
    89. 104. Heinz Headquarters, Pennsylvania Roofscapes, Inc.
    90. 105. In our every deliberation we must consider the impact of our decisions on the next seven generations. -The Great Law of the Iroquois Confederacy
    91. 106. Green Roofs in Germany
    92. 107. Green Curves
    93. 108. <ul><li>Working toward the green skyline of the future. </li></ul>Earth Our Only Home, Inc. This concludes The American Institute of Architects Continuing Education Systems Program Thank you for your time! ANY QUESTIONS??