David O. Prevatt, Ph.D., P.E. University of Florida Department of Civil and Coastal Engineering

Transcription

1 FBC: 10-BC Vegetative Roof Systems Design Guidelines for Performance in Hurricanes, Rain and Drought David O. Prevatt, Ph.D., P.E. University of Florida Department of Civil and Coastal Engineering 5 December 2011, Gainesville FL 1

2 Contact Information Principal Investigator David Prevatt, PhD, PE, Assistant Professor (352) x 1495 Associate Investigator Forrest Masters, PhD, PE, Assistant Professor masters@ce.ufl.edu, (352) x 1495 Participant Glenn Acomb, FASLA, Senior Lecturer, acomb@ufl.edu Dept. of Landscape Architecture, University of Florida 2

3 Commissioned Tasks at the University of Florida (a) Capture and present the most recent research on vegetative roofs in the public domain. Catalogue and compare the availability of vegetative roof systems (in Florida), their (wind) anchorage to the roof structures and installation and design criteria. (b) Conduct wind uplift test on full scale green roof and develop preliminary understanding of the performance in high winds. Identify typical Floridaappropriate green roof systems. Evaluate minimum biomass loss, scouring characteristics, and plant damage for moderate, strong and extreme winds. Determine effect of torrential rain on wind performance. Assess the rate of recovery of vegetation and effect of multiple wind storms. (c) Conduct parametric studies of factors affecting uproot resistance and plant breakage strength of plants used in vegetative roof systems, scour resistance for green roof systems. Develop a standardized test procedure for evaluating green roofs hurricane wind related performance and submit protocol to ASTM and the Green Roof Council to initiate national consensus standards development. 3

4 Current Industry in the U.S. Total green roof area (2011):12,400,000 ft 2 West Midwest Northeast West: 1,880,000 ft 2 (15%) Midwest: 4,260,000 ft 2 (34%) Northeast: 2,680,000 ft 2 (22%) South: 3,610,000 ft 2 (29%) South Florida 244,000 ft 2 of green roof area in Florida (<20 green roofs) 4

5 Florida s Green Roof Issues Plants and growth media Viability of plant selection in hostile conditions (drought & freeze compatibility) Weed suppression and biodiversity (native vs. nonnative plants) Heat flow Moisture residence Root depth issue due to the nature of Florida native plants evolution 5

6 Green Roofs in Florida After approximately 10 years of green roofs in Florida, it has been observed: Growing interest in Florida 4 roofs that are over 2,000 s.f. Primarily institutional, extensive, built-in-place Irrigated and planted native and/or ornamentals--(sedums failed) Complications due to freezes and weed outbreaks Issues code (lack of wind uplift research), lack of urgency for stormwater (no CSO s) and the challenges of a hot-humid climate. UF Perry Construction Yard UCF Student Union Clermont Honda Dealership 6

7 Morphology by Season March/April 2007 June 2007 Photograph at installation. Photos by Glenn Acomb Three months later exhibiting significant growth. June and July had the most successful bloom. (+2.5 months) 7

8 Morphology by Season October, 2007 January, 2008 Plants gone to seed and beginning to dieback. (+6 months) Combination of a two hard freezes and perennial dieback (presenting an issue of fuel). Perennials or non-evergreens are a concern if maintenance is not regular. (+9 months) 8

9 Morphology by Season October, 2007 January, 2008 Plants gone to seed and beginning to dieback. (+6 months) Combination of a two hard freezes and perennial dieback (presenting an issue of fuel). Perennials or non-evergreens are a concern if maintenance is not regular. (+9 months) 9

10 Morphology by Season July, 2009 May, 2010 Half of the original natives are thriving; weeds intrude and begin to thrive, leading to subsequent action - replanting. (+26 months) Weeding removed many and the bloom is beginning, but plant variety has been reduced by dominant species (5 out of 10) or due to removal for root depth concerns. (+36 months) 10

11 Green Roof Design Guidelines German FLL FM I-35 RP-14 VF-1 ASTM-E2396: Saturated Water Permeability of Granular Drainage Media ASTM-E2397: Determination of Dead/Live Loads on Green Roof Systems ASTM-E2398: Water Capture and Media Retention of Geocomposite Drain Layers ASTM-E2399: Maximum Media Density for Dead Load Analysis FM Global I-35: Green Roof Systems (Factory Mutual Insurance Company, 2007) ANSI/SPRI ANSI/SPRI German RP-14: FLL: VF-1: Green Wind External Roofing Design Fire Guideline Standard Design for Standard Vegetative for Roofing Vegetative (FLL, Systems 2008) Roofs (SPRI, 2010) 11 ASTM-E2400: Selection, Installation, and Maintenance of Plants for Green Roof Systems Guide

12 Green Roof Design Guidelines SPRI initiates discussion on prescriptive green roof standards NRCA: green roofs must comply with standards as other roofing assemblies GRHC & SPRI develops two standards: RP-14: Wind Uplift Design Guidelines VF-1: Fire Resistance Criteria for Green Roofs FM Global: specifies green roof fire testing protocol FM 4477:2010 Vegetative Roof Systems ( ) 12

13 NRCA-funded Green Roof Wind Uplift Test Evaluate the scour resistance of a fourinch deep fully vegetated growth media subject to 2-minute wind gusts greater than 90 mph. Determine the minimum vegetation coverage needed to resist growth media scour during a 2- minute 90 mph wind gust. Identify effective surface treatments that can minimize growth media scour and wind speeds at failure. Wind UpliA Test of Green Roof Modular Unit Retzlaff, Bill; Serdar Celik; Susan Morgan; (2009) Wind UpliA of Green Roof Systems, Southern Illinois University Edwardsville, IL. SubmiOed to Green Roof Blocks and the NaRonal Roofing Contractors AssociaRon March 12,

14 FBC: 10-BC Vegetative Roof Systems Appropriate to Florida: hurricane wind and rain October 2010: Preliminary Pilot Study Used hurricane simulator on a residential extensive green roof (3:12 slope) Despite lack of coverage ratio during testing, minimal losses motivated further research Roof is currently in storage and recovering Sloped green Profileroof viewinofstorage, sloped-green 1 year roof aftertest pilot study 14

15 Summer 2011: Modular Green Roof Wind Tests Grid System Hurricane Simulator Green Roof Modules Hydraulic Lift High Speed Cameras 15

16 Test Setup Wind Behavior Hurricane Simulator Simulated Roof 16 Side Top View

17 Scour Wind Action on Green Roofs Walter, B. et al. (2011) Measurements of surface shear stress distribu<on in live plant canopies, ICWE13, Amsterdam, The Netherlands (July 2011) 17

18 Wind Resistance Test Approach Establish 4 in & 8 in. deep green roof module trays Develop test system with 12 in. x 6 in. wide parapet Subject modular tray green roof system to six wind velocity ranges 20, 30, 50, 70, 90, and 120 mph. 20mph to 90 mph sustain 30 sec. and 120 mph for 60 sec. Monitor plant performance using video and photos Recovery and re-test in 8 months (adjust test time) Test a built-in-place roofing system with same plants 18

19 Phase 2: Modular Roof System Tests 50 modules tested in June additional (plus 50 re-tests) in June 2012 Tests on built-in-place roof (system: Hydrotech or Tremco) 4 in. tray 8 in. tray Growth media 19

20 Results Test Trial inch (before) (after) Module Weight Weight Loss (%) (lbs) 20

21 Plant Stalk Angles During Tests Test Trial 1 (4 ) MPH Test Trial 2 (4 ) Test Trial 3 (4 ) Test Trial 4 (8 ) 21

22 100 Results Plant Stalk Angle vs. Wind Speed Plant Stalk Angle with Horizontal (degrees) Wind Speed (mph) Test Trial 1 Test Trial 2 Test Trial 3 Test Trial 4 Average (Trials 1-3) 22

23 Remaining Tasks 1. Complete test trial (8 in. module tray full parapet) 2. Complete 8 in. tray test trial (remove back parapet) 3. Establish and test built-in-place green roof systems 4. Plant recovery and retesting of module tray systems Establish, test and compare longer established plants 5. Formulate and present wind design installation guide 23