Introduction to Green Roofs

Transcription

1 Introduction to Green Roofs

2 What is a green roof? A roof with a thin layer of soil and living vegetation installed on top of conventional flat or sloping roofs

3 How do green roofs work? evapotranspiration

4 Related Practices / Terms Ecoroofs Landscapes over structure Living roofs Roof gardens Vegetated roofs

5 Ancient Roof Garden Origins Roof gardens originated in ziggurats, or temple structures of ancient Mesopotania The Hanging Gardens of Babylon are the most well-known example

6 Later Roof Gardens Rockefellor Center Building, New York City, constructed Typical of trendy hotel and penthouse gardens overlooking Central Park

7 Later Roof Gardens Derry and Toms Building, London Constructed in 1938

8 Green Roof Origins Scandinavian and Icelandic turf roofs, common from 6 th to19 th centuries Turf provided protection of underlying birch bark waterproofing

9 Green Roof Origins Sod roofs in upper midwest plains states, late 1890 s Sod was used to construct both walls and roofs of soddie houses Sod was also used for roofing on dugout house construction

10 20 th Century Green Roof Development Contemporary green roof construction originated in Germany in the 1960 s Arose out of need to compensate for lost open space and overdrawn aquifers Germany has become the world leader in green roof systems and mandates

11 U.S. Green Roofs: Chicago Former Chicago Mayer Richard Daley aspired to make Chicago the greenest American city Chicago claims to have more green roofs than any other American city One of its first green roofs was retrofitted on Chicago s City Hall

12 Green Roofs in the Pacific Northwest Portland, Seattle, and Vancouver are national leaders in projects, incentives, and research Portland Building Seattle City Hall Seattle Public Library Ballard Branch Vancouver Convention Centre

13 Economic Benefits Regulates building temperatures Reduces building heating and cooling costs Fulfills LEED credits Maximizes utilization of urban space Increases property values Prolongs the life of a roofing materials by protection from physical damage, ultraviolet radiation, and temperature extremes Integrates well with other sustainable building practices - rainwater harvesting and reuse for irrigation and toilet flushing

14 Environmental Benefits Slows rate and volume of rainwater runoff Filters pollutants in rainwater runoff Provides habitat for butterflies, birds, beneficial garden insects Reduces atmospheric CO2 Captures dust, soot, and other air-borne pollutants Minimizes urban heat island effect Moderates root top ambient air temperatures

15 Social Benefits Offsets loss of open space in dense land developments Provides space for urban agriculture and community gardens Creates landscape amenities, such as recreational and open space Attenuates noise Provides educational opportunities in school settings Offers therapeutic garden space in hospitals, nursing homes, etc Improves visual quality of conventional roofs

16 Typical Green Roof Assembly plants soil filter layer drainage layer protection layer waterproof membrane insulation vapor barrier roof deck

17 Types of Green Roofs: Extensive Built primarily for environmental benefits Have thin vegetation and soil layers Soil depths up to 6 inches Roof loads are typically pounds per square foot Typically not designed for accessibility as a garden or open space Frequently designed to satisfy specific stormwater performance goals

18 Intensive Green Roofs Often designed as roof top gardens Soil depths are a minimum 12 Vegetation may include perennials, shrubs, and trees Construction may include elaborate irrigation and drainage systems Roof loads range from pounds per square foot Typically designed as landscapes over structures parks, lawns, rooftop gardens, etc.

19 Where can green roofs be used? barns chicken coops dog houses garden sheds garages / workshops houses house boats multifamily dwellings

20 Commercial / Industrial Green Roofs Ford Motor Company truck assembly plant, Dearborn MI 10.4 acre green roof Functions as part of a 600 acre integrated stormwater management system Designed by William McDonough + Partners in 2003

21 Parks, Educational, and Visitor Centers Cedar River Watershed Education Center, Cedar Falls WA Includes living roof over covered walkway Site includes water conservation, stormwater detention, and water quality wetland demonstration features Designed by Jones + Jones Architects and Landscape Architects, 2001

22 Where else can green roofs be used? highway overpasses transportation tunnel lids underground parking garage lids Freeway Park, Seattle Olympic Sculpture Park, Seattle High Line Park, New York City

23 Green Roof Project Success A successful execution requires interdisciplinary design team: architect horticulturalist landscape architect maintenance personnel planning agency structural engineer waterproofing / roofing system consultant

24 Design Considerations Structural loading Roof deck slope 2-5% ideal Growing media light weight, well draining, moisture holding capacity, stable ph Plant selection: shallow rooted, low growing, drought tolerant, climate appropriate Drainage system Irrigation system Fire code restrictions and wind design standards Security and fall protection

25 Installation Considerations Hire an experienced contractor Protect waterproofing membrane from damage or puncture Test waterproofing membrane for leaks before installing full vegetated roof assembly Install 10% more growing media than specified to account for settling Plant by direct seeding, plug transplants, pre-grown mats, or modular tray systems Apply mulch, netting, or wind blanket to protect from wind scouring Warranties can insure against defective products and/or inadequate installation

26 Maintenance Maintenance should be provided by trained professionals twice per year Weeding Top-dressing with compost Slow-release fertilizer application Leak detection: Spray testing Standing water flood testing Flowing water testing Dlectric leak detection Check drains and scuppers for clogging caused by sediment or debris accumulation

27 Approximate Cost Comparisons New extensive green roof construction: $10-20 per square foot installed Retrofitted extensive green roof: $6-40 per square foot installed New conventional roofing $3 15 per square foot installed Conventional reroofing: $10 35 per square foot installed

28 Cost Considerations Houses May be more cost prohibitive for single family home construction Potentially higher cost for constructing a stronger weight-bearing roof Commercial buildings Green roof loading is comparable to loading weights of HVAC systems Special structural engineering may not be required May have greater energy cost savings on existing building retrofits than new construction built to current energy code standards Costs increase with publically accessible green roofs structural engineering for live loads, railings, etc.

29 Challenges Plants are exposed to greater wind velocities and temperature extremes Wind scouring of growing media Temperature extremes Irrigation needs Lightweight soil mixes with thin profiles dry out quickly Seasonal variation - pacific northwest summer drought Lack of significant published engineering standards Few enforceable warranties Potentially cost prohibitive compared to other LID practices Return on developer investment seems to be reliant on municipal incentive programs

30 Print Resources

31 Web Resources Green Building Research Laboratory Green Roof Energy Calculator: Green Roof Info Think Tank (GRiT): Greenroofs.com : The Greenroof Industry Resource Portal Green Roofs for Healthy Cities: greenroofs.org International Green Roof Association: livingroofs.org The MIT Design Advisor: Portland Bureau of Environmental Services Ecoroof Program: Whole Building Design Guide Extensive Vegetative Green Roofs:

32 Professional Resources Built Green Guideline for the Planning, Execution and Upkeep of Green-Roof Sites - Richlinien für die Planung, Ausführung and Plege von Dachbegrünung National Roofing Contractors Association guidelines for waterproofing with vegetated roofs: nrca.net Northwest Ecobuilding Guild: Peninsula College Green Construction and Remodeling program Seattle Central Community College Sustainable Building Advisor Institute certificate program University of Washington Professional & Continuing Education U.S. Green Building Council WSU Extension LID Technical Workshop Series

33 References Bureau of Environmental Services. Ecoroof Handbook City of Portland, OR: Bureau of Environmental Services. Ecoroof Incentives. City of Portland, OR: Retrieved August 8, 2011 from Hinman, Curtis. Low Impact Development: Technical Guidance Manual for Puget Sound. Olympia: Puget Sound Action Team, January Hopper, Leonard J. Landscape Architectural Graphic Standards: Student Edition. 2 nd Ed. Hoboken, New Jersey: John Wiley & Sons, Inc., Kloss, Christopher. Managing Wet Weather with Green Infrastructure Municipal Handbook:: Rainwater Harvesting Policies. United States Environmental Protection Agency Publication EPA-833-F , December Leung, Julia. Rainwater Harvesting 101. Council on the Environment of New York City. New York, New York: August Miller, Charlie. Extensive Vegetated or Green Roofs. 20 August January Natural Resource Conservation Service. Water Harvesting Catchment. Conservation Practice Standard 636. United States Department of Agriculture : September Small Green Roofs: Low-Tech Options for Greener Living - Nigel Dunnett, Dusty Gedge, John Little, & Edmund C. Snodgrass Symes, Michael. A Glossary of Garden History. Great Britain: CIT Printing Services, University if Arkansas Community Design Center. Low Impact Development: A Design Manual for Urban Areas. Fayatteville: University of Arkansas Press, 2010.

34 Image Credits Slide 1, left to right: Slide 2: Slide 3: Low Impact Development: A Design Manual for Urban Areas Slide 4: Slide 5: Slide 6, left to right: Slide 7, left to right: Slide 8, left to right: Slide 9, left to right: Slide 10, left to right: Slide 11:

35 Image Credits Slide 12, left to right: _Photo_Credit_Nic_Lehoux.jpg Slide 13: Slide 14: Slide 15: Slide 16: Slide 17: Slide 18: Slide 19, left to right : Slide 20: Slide 21: Slide 22, left to right: Slide 23: Slide 24: Slide 25: Slide 26: Slide 27: Slide 28: Slide 29: Slide 30: Slide 32:

36 Acknowledgements This project has been funded wholly or in part by the United States Environmental Protection Agency under assistance agreement PO-00J08601 to Jefferson County Department of Community Development. The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.