Final Repor tTa p p i n g t h e P o t e n t i a l o f U r b a n R o o f t o p sRoof top R e so u rce s N e igh borhood A s...
Final Repor tTa p p i n g t h e P o t e n t i a l o f U r b a n R o o f t o p sRoof top R e so u rce s N e igh borhood A s...
TABLE OF CONTENTS1.   EXECUTIVE SUMMARY/INTRODUCTION ........................................................ 1-12.   EXIS...
B    A Y L O C A L I Z ET    A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR    O O F T O P R E S O U R...
1   EXECUTIVE SUMMARY/INTRODUCTION    “Built-out” is a phrase often used in planning and development fields to de-    scri...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
B A Y L O C A L I Z      E             T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P            S     ...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
B A Y L O C A L I Z      E           T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P            S     R ...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
2   EXISTING CONDITIONS    This chapter describes the current state of rooftop resource implementation    in the Bay Area ...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
B A Y L O C A L I Z E            T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S      R O O F T O P R ...
BAY LOCALIZE                                                                                                        ROOFTO...
B A Y L O C A L I Z E          T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S    R O O F T O P R E S ...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
B A Y L O C A L I Z E          T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S    R O O F T O P R E S ...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
B A Y L O C A L I Z E             T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S       R O O F T O P ...
B A Y L O C A L I Z E                                        T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T...
B A Y L O C A L I Z E            T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S      R O O F T O P R ...
B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N ...
B A Y L O C A L I Z E          T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S    R O O F T O P R E S ...
BAY LOCALIZE                                                                                                         ROOFT...
3   ROOFTOP RESOURCE PROTOTYPES    For the purposes of this assessment, five rooftop resource prototypes were    developed...
B   A   Y L O C A L I Z E                                          T   A   P P I N G T H E P O T E N T I A L O F U R B A N...
B AY L O C A L I Z E                                                               R o o f t o p   R e s o u r c e s   N e...
B   A   Y L O C A L I Z E                                            T   A   P P I N G T H E P O T E N T I A L O F U R B A...
B A Y L O C A L I Z E            T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S      R O O F T O P R ...
B   A   Y L O C A L I Z ET   A   P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR   O   O F T O P R E S O ...
B A Y L O C A L I Z E            T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S      R O O F T O P R ...
B   A   Y L O C A L I Z E                                          T   A   P P I N G T H E P O T E N T I A L O F U R B A N...
B AY L O C A L I Z E                                                                             R o o f t o p    R e s o ...
B   A   Y L O C A L I Z E                                      T   A   P P I N G T H E P O T E N T I A L O F U R B A N R O...
B A Y L O C A L I Z E            T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S      R O O F T O P R ...
B   A   Y L O C A L I Z ET   A   P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR   O   O F T O P R E S O ...
B A Y L O C A L I Z E             T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S       R O O F T O P ...
B AY L O C A L I Z E                                                                     R o o f t o p   R e s o u r c e s...
B A Y L O C A L I Z E           T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S     R O O F T O P R E ...
B   A   Y L O C A L I Z E                                           T   A   P P I N G T H E P O T E N T I A L O F U R B A ...
B A Y L O C A L I Z E         T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S   R O O F T O P R E S O ...
B AY L O C A L I Z E                                                                    R o o f t o p   R e s o u r c e s ...
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
Tapping the Potential of Urban Roof Tops
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Tapping the Potential of Urban Roof Tops

  1. 1. Final Repor tTa p p i n g t h e P o t e n t i a l o f U r b a n R o o f t o p sRoof top R e so u rce s N e igh borhood A s s e s s m e nt October 31, 2007 D E S I G N , C O M M U N I T Y & E N V I R O N M E N T
  2. 2. Final Repor tTa p p i n g t h e P o t e n t i a l o f U r b a n R o o f t o p sRoof top R e so u rce s N e igh borhood A s s e s s m e nt Bay Localize is an Oakland-based organization that catalyzes a shift from a globalized, fossil fuel-based economy to a localized green economy that strengthens all Bay Area communities. Bay Localize is a nonprofit project of the Earth Island Institute. This report is generously supported by the Community Foundation Silicon Valley, Laurence Levine Charitable Fund, San Francisco Foundation, Ollie Fund, and Bay Localize supporters. It was prepared by Brian Holland and Sarah Sutton of Design, Community and Environment, Kate Stillwell of Holmes Culley, and Ingrid Severson and Kirsten Schwind of Bay Localize. For more information, contact: Bay Localize 436 14th Street, Ste 1127 Oakland, CA 94612 510-834-0420 www.baylocalize.org October 31, 2007 D E S I G N , C O M M U N I T Y & E N V I R O N M E N T
  3. 3. TABLE OF CONTENTS1. EXECUTIVE SUMMARY/INTRODUCTION ........................................................ 1-12. EXISTING CONDITIONS .............................................................................. 2-13. ROOFTOP RESOURCE PROTOTYPES ............................................................. 3-14. FINDINGS .................................................................................................. 4-1AppendicesAppendix A: Assumptions and Methodology i
  4. 4. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TT A B L E O F C O N T E N T SList of FiguresFigure 2-1. Aerial view of buildings in study area with existing rooftop resources....................................................................... 2-4Figure 2-2. Aerial view of study area indicating distribution of building types. ......................................................................... 2-14Figure 3-1. Cross-section of Extensive Green Roof Prototype. .................. 3-3Figure 3-2. Cross-section of Intensive Green Roof—Vegetables prototype................................................................................... 3-9Figure 3-3. Cross-section of intensive Green Roof—Herbs prototype................................................................................. 3-14Figure 3-4. Cross-section of Rooftop Hydroponic Garden prototype................................................................................. 3-18Figure 3-5. Diagram of assembly of rainwater catchment system using 50-gallon drum. .................................................. 3-24Figure 3-6. Diagram of integrated Rainwater Harvesting and Solar Photovoltaics prototypes. .............................................. 3-25Figure 4-1. Aerial view of study area with buildings assigned rooftop resources prototypes. ................................................... 4-3List of TablesTable 2-1 Building Typology-Typical Characteristics ............................ 2-12Table 2-2 Building Type Distribution..................................................... 2-13Table 3-1 Prototype Characteristics.......................................................... 3-2Table 4-1 Prototype Assignment and Productivity ................................ 4-10ii
  5. 5. 1 EXECUTIVE SUMMARY/INTRODUCTION “Built-out” is a phrase often used in planning and development fields to de- scribe dense, urban communities that have few remaining vacant buildable parcels. As the Bay Area adopts smart growth and transit-oriented develop- ment policies emphasizing high-density housing, neighborhoods throughout San Francisco, the East Bay, Peninsula, and South Bay are becoming increas- ingly built-out. This density presents a challenge in identifying available land for important uses such as open space, community gardens, and stormwater and energy infrastructure. In cities across the country, however, a new land- scape is being discovered where building rooftops meet the sky. Previously regarded as unusable space, the landscape of rooftops is being re- claimed for productive and sustainable purposes. Whereas in the past, roofs have been a liability—emitting heat into the urban atmosphere, shedding pol- lutants into the watershed, requiring costly repair and replacement—some cities are transforming roofs into assets. They are being used as catchment areas for irrigation water, renewable energy platforms, recreational open space, food and educational gardens, reduction of stormwater surges, and aes- thetic improvement. In short, rooftops are being harnessed to improve cities and enhance the quality of life of inhabitants. A rooftop resource development philosophy is emerging and taking root in the Bay Area. Building owners and developers are looking at the options of solar power, rainwater catchment and living roofs to maximize their build- ings’ efficiency and function. Designers and planners are coming together to map out strategies for green roof implementation. Public works departments and utilities are stimulating adoption of solar photovoltaic systems. And citi- Rooftop garden atop St. Simon Stock Catholic School Bronx, New York. zens are seeking ways to better utilize rooftops for energy, food and commu- Source: St. Simon Stock Catholic nity empowerment. School. I. PROJECT OBJECTIVES Information on green roofs, solar technologies, and rainwater harvesting is available in abundance. This study seeks to fill gaps in that knowledge, par- 1-1
  6. 6. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X E C U T I V E S U M M A R Y / I N T R O D U C T I O Nticularly with regard to low-cost strategies on existing buildings and the po-tential productivity for future developments. The study analyzes rooftopresource implementation and benefits for the Eastlake district in Oakland.Objectives include: ♦ Analysis of the suitability of rooftop resource strategies in different built contexts, highlighting retrofits to existing buildings without structural improvement; ♦ Design of conceptual rooftop resource prototypes that are feasible for ex- isting buildings; ♦ Analysis of productivity for edible garden designs on future development in the area; and ♦ Quantification of the productivity benefits of rooftop gardens, renewable energy, and rainwater catchment technologies.Several unique contributions are addressed in this study, including: ♦ Focus on Existing Buildings. Most informational resources for green roof development focus on new construction; therefore, less information is available for building owners and policymakers to use when consider- ing the potential for green roof retrofits on existing buildings. ♦ Regional Context. Much of the available information on green roofs was developed in different social, political, economic, environmental and meteorological contexts, from Chicago to Germany to Portland to Mont- real. Also, while rooftop resource development in cities across the US and the globe is supported with public financial incentives, the Bay Area and the state of California fall short in implementing many of these poli- cies. ♦ Urban Agriculture. This study also differs from many existing docu- ments in that an emphasis is placed on rooftop vegetable gardening as a strategy for intensifying urban agriculture activities, which can improve nutrition and food security in urban neighborhoods while reducing de- pendence on an energy-intensive global food economy.1-2
  7. 7. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X E C U T I V E S U M M A R Y / I N T R O D U C T I O N ♦ Neighborhood Scale. This study looks beyond the analysis of green roof benefits at the building scale to focus primarily on projecting out- comes at the neighborhood scale.II. PROJECT APPROACHAs detailed in later chapters, this assessment analyzes the potential for greenroofs, rooftop gardens, solar photovoltaics, and rainwater harvesting on exist-ing buildings and future developments, and identifies possible benefits to theEastlake neighborhood in Oakland. A model was developed for this study toproduce quantitative estimates of rooftop productivity.Buildings in the Study Area were categorized into types to generalize theircharacteristics, including the weight-bearing capacity of the roof structure.Rooftop resource prototypes were then designed to serve as test retrofits,providing data on loading characteristics. The prototypes were tailored tomeet the special needs of existing buildings and were correlated with produc-tivity estimates per square foot. Prototypes were then assigned to each build-ing based on their suitability. Vacant lots were categorized as “opportunitysites” that could hold intensive, edible roof gardens. Finally, the total areaand productivity estimates of each prototype were used to determine aggre-gate benefits to the Eastlake Study Area.III. PROJECT FINDINGSThe findings of the assessment demonstrate a great deal of potential for har-vesting food, energy, and water on Bay Area roofs. Rooftop gardens, solarphotovoltaic systems, and rainwater harvesting technologies can all be fittedon existing buildings. There are clear opportunities and constraints to eachstrategy as well as some surprising benefits. In addition to well-documentedbenefits such as water quality and energy efficiency improvements, provision 1-3
  8. 8. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X E C U T I V E S U M M A R Y / I N T R O D U C T I O Nof open space amenities, and aesthetic appeal, rooftop resources in the StudyArea can provide: ♦ Clean, renewable electricity satisfying approximately 25 percent of de- mand; ♦ Fresh, leafy-green vegetables for all area residents; and ♦ Supplemental rainwater for irrigation for approximately 83 percent of the area’s buildingsThese benefits are attainable, but not without significant effort invested byState and local government, the private sector, communities and individualhouseholds.IV. REPORT STRUCTUREThe report is organized into four chapters: Introduction, Documentation ofExisting Conditions, Description of the Rooftop Resource Prototypes, andStudy Findings. Methodological approaches and assumptions are described inthe text or footnoted, and also described in greater depth in Appendix A.Figures are distributed throughout the text to provide accessible graphic illus-tration of concepts.V. ACKNOWLEDGEMENTSPreparation of this study was aided by several professional advisors andcommunity volunteers. Deserving of special acknowledgement are: ♦ American Soil and Stone ♦ Andrea Solk, Sustaining Ourselves Locally ♦ Association of Bay Area Governments ♦ Babak Tondre ♦ Center For Sustainable Economy1-4
  9. 9. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X E C U T I V E S U M M A R Y / I N T R O D U C T I O N ♦ City Slicker Farms ♦ Community Foundation Silicon Valley ♦ Institute for Simplified Hydroponics ♦ Intertribal Friendship House ♦ Laurence Levine Charitable Trust ♦ Mark Richmond, Practica Consulting ♦ Natylie Baldwin ♦ Rana Creek ♦ REC Solar ♦ San Francisco Planning and Urban Research Association (SPUR) ♦ Stewart Winchester, Merritt College ♦ Tufani Mayfield ♦ United Nations Food and Agriculture OrganizationBuilding Survey VolunteersAaron LehmerAndrea MannBob StrayerCarolyn BushCharles HardyDavid JaberDebbie CollinsDominic PorrinoEllen DoudnaInga SheffieldKelley LakeKirsten SchwindLisa KatzMaija DzenisMark McBethNelson ChickOliver LearPaula White 1-5
  10. 10. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X E C U T I V E S U M M A R Y / I N T R O D U C T I O NSarah KennedySharon KutzVI. CONCLUSIONThis Neighborhood Assessment conclusively demonstrates that rooftop re-sources can be developed on existing buildings in the Bay Area without struc-tural improvements. Furthermore, future developments would gain consid-erable benefits by planning for intensive, edible roof gardens. Hydroponicrooftop gardens and solar photovoltaics show the most promise for existingbuildings, while intensive and extensive green roofs and rainwater harvestingpresent additional challenges, some of which may be overcome in time ifgreater investment is warranted. Today, it is possible for building owners toinstall rooftop technologies and improve water quality, save energy, growfresh produce, generate clean electricity, and contribute to greater communityresilience and livability. The promise of a healthier environment and greaterresource security makes it imperative that we begin planning and implement-ing for these sustainable rooftop systems now.Education and leadership can bring about the kinds of benefits that so manycities have successfully demonstrated. Policy and government support areessential keys to fostering the implementation of these systems. Rooftops arecurrently untapped resources and a package of appropriate design, develop-ment incentives, and public support is crucial to fulfilling their great poten-tial.1-6
  11. 11. 2 EXISTING CONDITIONS This chapter describes the current state of rooftop resource implementation in the Bay Area and specifically in the Study Area. It also documents the ar- chitectural history and existing demographic and regulatory setting of the Eastlake neighborhood in order to identify dynamics that may affect rooftop resource development. The latter half of the chapter presents the Building Typologies that were developed for the purposes of the assessment and de- scribes their distribution in the Study Area. I. ROOFTOP UTILIZATION The role of rooftops has historically been a peripheral consideration in the development of urban infrastructure and largely remains an afterthought in water, food and energy systems planning. Roofs have been used for collecting water or insulating homes for millennia, but widely-held perceptions dismiss these traditionally “low-tech” strategies as being old-fashioned or only appli- cable in rural contexts. While solar thermal and photovoltaic technologies have been applied on roofs for decades, these practices have yet to gain wide- spread adoption. However, new interest in green building is once again fo- cusing attention on rooftops. Green roofs, rainwater harvesting systems, and rooftop photovoltaics are being installed at an increasing rate while California Buildings within study area. Source: Ingrid remains a national leader in solar electricity generation. Severson. A. Rooftop Utilization in the Bay Area The Bay Area is well-known for its focus on environmental sustainability and for good reason. With regards to rooftop resource strategies, the region is ahead of the curve but far from taking full advantage of its resources. 2-1
  12. 12. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X I S T I N G C O N D I T I O N S1. Solar Photovoltaic InstallationsIn the nine-county Bay Area, over 5,000 photovoltaic systems have been in-stalled.1 The largest include the 675 kilowatt (kW) installation on the City ofSan Francisco’s Moscone Center, a 766 kW system at the Rodney StrongWinery in Healdsburg, and Alameda County’s 1,180 kW installation on theSanta Rita Jail in Dublin. In addition, much of the region’s photovoltaic ca-pacity exists in smaller systems under 15 kW, many of which serve residentialbuildings. In seven counties of the Bay Area (excluding Napa and SolanoCounties), these systems comprise approximately 18,000 kW, or 18 mega-watts (mW) of electricity generating capacity.22. Green Roofs and Rooftop GardensDespite a number of high-profile green roof projects in the Bay Area, thegreen roof trend has been somewhat slow to take hold in the region. An out-standing exception is the Gap Headquarters in San Bruno, which was con-structed with a 69,000 square-foot extensive green roof in 1997. The Califor-nia Academy of Sciences building under construction in San Francisco’sGolden Gate Park will also have a large, extensive green roof. Intensive greenroofs and rooftop gardens and parks have also been built, including park en-vironments atop parking garages at Civic Center, Yerba Buena Gardens andthe North Beach Place mixed-use project in San Francisco, and at the KaiserCenter office complex in downtown Oakland.Nevertheless, a number of cities have consistently outperformed Bay Arealocations in terms of green roof implementation, including Chicago, Wash-ington D.C., New York City and Portland, Oregon.3 As far as could be de-1 Liz Merry, “Status of Photovoltaic Installations in California,” Solar Energy ResourceGuide, NorCal Solar, 2007.2 Ibid.3 Green Roofs for Healthy Cities, “Green Roof Industry Survey Final Report,”http://www.greenroofs.org/storage/2006grhcsurveyresults.pdf (accessed April 14,2007).2-2
  13. 13. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N Stermined, no municipalities in the Bay Area region have green roof incentiveprograms as do Chicago and Washington, D.C.3. Rainwater HarvestingRegional attention to harvesting rainwater has fluctuated with concerns overenvironmental conditions or scarcity. Many residents discovered rainwaterharvesting, for example, in the drought of 1976-77, when reservoirs across theregion were dangerously drawn down and mandatory restrictions were im-posed on water use. While data on regional rainwater catchment implemen-tation is unavailable, it is likely that a limited number of residential buildingsare fitted with rainwater harvesting systems, and that this number is increas-ing, albeit very slowly, with elevated awareness of California’s water resourceand sustainability challenges.B. Rooftop Utilization in the Study AreaA limited level of rooftop utilization is already occurring in the Study Area.There are at least six rooftop solar water heating installations, all on apart-ment buildings. There are no green roofs on occupied buildings in the area,but a vegetated plaza sits atop an underground parking structure. The plaza is Volunteers identifying building types. Source:planted with a variety of trees, grasses, and shrubs, providing an attractive DC&E.semi-public space with stormwater retention benefits. It is possible that somerainwater harvesting systems are in use but none were identified through ae-rial photograph analysis or the field survey. Figure 2-1 illustrates existingrooftop resources in the area.II. REGULATORY AND POLICY SETTINGThe Study Area is within the jurisdictional boundary of the City of Oaklandand is subject to a number of State and City regulations pertaining to rooftopuses. This section introduces these regulations and their applicability to thestudy. 2-3
  14. 14. BAY LOCALIZE ROOFTOP RESOURCES NEIGHBORHOOD ASSESSMENT E. 19th St. d. Blv rk Pa E. 18th St. St . 8 th E. 1 E. 17th St. Lake Merritt Foothill Blvd. . vd Bl e or sh ke La E. 15th St. 1st Ave. 2nd Ave. 3rd Ave. 4th Ave. 5th Ave. 6th Ave. 7th Ave. 8th Ave. International Blvd. Clinton Square Park E. 12th St. E. 11th St. E. 10th St. Intensive Green Roof No Resource 0 250 500 Feet Solar Water Heating Study AreaFigure 2-1. Aerial view of buildings in study area with existing rootop resources.
  15. 15. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N SA. Zoning CodeThe Zoning Code is contained in Title 17 of the City of Oakland’s MunicipalCode. The Code classifies, regulates, restricts and segregates land uses, build-ing characteristics, and population densities according to the land use goalsestablished by the community in the General Plan. Minimum requirementsfor usable open space are established for residential uses. In Chapter 17.126,the Code sets minimum standards for usable open space on residential parcels,including rooftop uses.Residential parts of the Study Area are mostly zoned R-50 (Medium DensityResidential) or R-60 (Medium-High Density Residential), with the remainder Mixed use building. Source: DC&E.zoned at higher densities. Usable open space requirements for these classifica-tions range from 150 to 200 square feet per dwelling unit. Rooftop areas cansatisfy a maximum of 20 percent of this required open space, or 30 to 40square feet per dwelling unit.B. California Building CodeThe State Building Code is contained in Title 24, Part 2 of the CaliforniaCode of Regulations. The Code regulates the construction and function ofbuildings to ensure fire and life safety and adequate structural design. Perti-nent sections of the code include Chapter 5, Section 509 (Guardrails), Chapter10 (Means of Egress), Chapter 13, Section 1301 (Solar Energy Collectors),Chapter 15 (Roofing and Roof Structures), and Chapter 16 (Structural DesignRequirements). The following considerations will affect the extent to whichusable rooftop spaces can be created.1. Occupancy Load and Means of EgressSince construction of an accessible space on a rooftop alters the use of theroof, the municipal Building Department will ensure that Building Code re-quirements are met when reviewing plans for the improvement. Code re-quirements will vary depending on how the occupancy of the roof space is 2-5
  16. 16. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X I S T I N G C O N D I T I O N Sdefined and on the maximum number of occupants expected and allowed touse the space, which is the “occupant load.”The most relevant example is with regard to means of egress.4 Accessible roofspaces that accommodate many occupants will be required to provide morethan one exit, while spaces intended for ten or fewer occupants are adequatelyserved by one exit. This is a critical variable for rooftop gardening since veryfew buildings have two exits from the roof. Therefore, for rooftop gardeningto be possible, the Building Department must ensure safety by either callingfor two exits or determining that the rooftop garden’s occupancy load will beten or less, rendering one exit sufficient.The Building Department is responsible for assigning an occupancy load tothe rooftop space, in accordance with the following direction from Chapter10, Section 1003 of the California Building Code: ♦ Areas with fixed seats. Occupant load for areas with fixed seats is de- termined by assigning one occupant per seat provided in the area. For example, an area with 12 seats has an occupant load of 12. ♦ Areas without fixed seats. Here the occupant load is determined by di- viding the occupied square footage by an “occupant load factor” in Table 10-A of the California Building Code. For uses not included in the table, such as gardening, a factor for a similar type of use will be used. Specula- tively, a case could be made that gardening is similar in intensity of use to such uses as manufacturing or a commercial kitchen, where a limited number of people are involved in a productive activity over a large area. If these factors are used, as much as 2,000 square feet can be occupied for gardening without exceeding the maximum desirable occupant load of 10.Because rooftop gardening is a relatively rare phenomenon in the region, nointerpretation of the Code with regards to occupancy has been established. It4 Means of egress are Code-compliant exits. Any occupiable space, such as a rooftopgarden, must have at least one Code-compliant means of egress.2-6
  17. 17. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N Sis possible that Code officials will be wary of rooftop uses more intensivethan gardening and will consider the space a gathering place, thereby requir-ing an additional exit. The outcome will depend on the municipality and onassurances that can be made to limit the number of occupants.2. GuardrailsChapter 5 of the Building Code requires a guardrail around habitable space inorder to protect life safety. Some buildings in the Study Area have fixed para-pets lining the perimeter of the roof area and extending as high as a few feet.Others have no perimeter barrier at all. In any case, a code-compliance bar-rier that extends 42 inches in height is required.C. AccessibilityLocal, State, and federal governments address accessibility for the mobility-impaired through several codes and laws. At the federal level, the Americanswith Disabilities Act (ADA) requires that equal access be provided for themobility-impaired when alterations to public spaces are made. Chapter 11 ofthe California Building Code also sets forth stipulations for accessibility,which are enforced by municipal Building Departments. Both the ADA andChapter 11 must be satisfied.1. Americans with Disabilities Act ComplianceADA requirements for building alterations do not apply to buildings that areused for strictly residential purposes; only buildings considered “public ac-commodations”—such as restaurants, hotels, theaters, doctors’ offices, phar-macies, retail stores, museums, libraries, parks, private schools, and day carecenters—are subject to ADA rules. Some rooftop garden retrofits that areaccessible to the public would fall under ADA and would need to includeaccessibility features to the roof, in the form of either elevators or ramps. It islikely that these features would prove prohibitively expensive to install andwould create a major disincentive for creating accessible rooftop spaces onexisting buildings. 2-7
  18. 18. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X I S T I N G C O N D I T I O N SADA requirements apply only to public accommodations and do not addressresidential environments. Even for public accommodations, elevators wouldnot be required in many cases. According to the Department of Justice, ele-vators are generally not required in facilities under three stories or with fewerthan 3,000 square feet per floor, unless the building is a shopping center ormall; the professional office of a health care provider; a terminal, depot, orother public transit station; or an airport passenger terminal.5 In addition,accessibility requirements may be waived as an undue hardship if accessibilityfeatures cost more than 20 percent of the total alteration cost, which wouldapply in the case of rooftop gardens.2. California Building Code, Chapter 11Accessibility requirements in the State Code are similar to ADA require-ments, but also include residential uses in their scope. Like the ADA, theCode allows for exemptions based on “unreasonable hardship,” which waivesaccessibility requirements when the cost of accessibility features exceeds 20percent of the total alteration cost, and the total alteration cost is less than$120,000 (both of which are true for rooftop gardens). Installation of a newelevator in an existing building in order to access a new garden on the roofmay be acknowledged as unreasonable hardship, particularly if the structureis not a major commercial or institutional building.Every effort should be made to provide universal accessibility to rooftop gar-dens when feasible. The Americans with Disabilities Act and CaliforniaBuilding Code require that these improvements be made whenever feasible,but may provide flexibility when the costs of accessibility improvements areunreasonably high, as with elevator installation in existing residential struc-tures and other small buildings.5 US Department of Justice, “Americans with Disabilities Act Questions and An-swers,” http://www.usdoj.gov/crt/ada/qandaeng.htm.2-8
  19. 19. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N SIII. STUDY AREA CHARACTERISTICSComprising roughly one-quarter of a square mile, the Study Area consists ofthe Eastlake commercial district and surrounding residential neighborhoodssoutheast of Lake Merritt in Oakland. The area provides a fertile testingground for rooftop resource feasibility due to its great diversity, both in itssocioeconomic conditions and its built environment.A. Demographics Mixed-use building on 2nd Avenue.Eastlake is a unique neighborhood demographically, presenting a complexmix of economic and ethnic attributes in a compact area. Extrapolation ofcensus data suggests that the Study Area is home to approximately 7,000 resi-dents in approximately 3,500 dwelling units. The median income of around$31,000 is low relative to the City of Oakland as a whole, but the number ofpeople below the poverty line is lower than the city average.6 A wide rangeof income levels exists in the area.The neighborhood is widely perceived as one of the most ethnically diverse inthe region. Dozens of languages are spoken by immigrants from around the Pitched-roof houses.world. Asians and African-Americans are the largest ethnic groups, compris-ing roughly one-quarter of the population each, with Hispanics accountingfor another 14 percent and the remainder White, or other races. Of residentswith Asian ancestry, many trace their roots back to Vietnam and otherSoutheast Asian countries. Parking garage in study area. Source: Ingrid Severson.6 Estimates based on U.S. Census Bureau, U.S. Census 2000. 2-9
  20. 20. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N S B. Architectural History Known variously over the years as Rancho San Antonio, Clinton, Brooklyn, and New Chinatown, Eastlake is a neighborhood with a complex and fasci- nating history that is reflected in the building stock found there today. While the built remnants of the Ohlone communities that originally occupied this area have disappeared, historic features dating back to Spanish settlement can still be found. San Antonio Park, lying just southeast of the study area, once served as the main plaza of Rancho San Antonio, the cattle ranch started by the East Bay’s original Spanish settlers in the 1820s. Apartment tower. The area was incorporated into Oakland in 1872. At least one 19th century home still stands in the neighborhood, along with several early 20th century Victorian homes. Many multi-family residential and commercial buildings found in the area today were constructed in the early 20th century, leading up to World War II. After the War, Eastlake experienced the same pattern of disinvestment that impacted many urban neighborhoods across the country. Deteriorating buildings continue to impact quality of life in Eastlake today and many structures in the study area are in fair or poor condition. Mid- century urban renewal projects also had an effect with hundreds of structures demolished in these decades and replaced with apartment buildings—1,108 “Shops” building type. apartments in 57 buildings total.7 Many of these renewal-era buildings are still found in the study area and factor significantly into the rooftop resource assessment. Since the era of urban renewal, the built conditions of the study area have not changed as rapidly. Investment in the 1980s and 1990s was primarily directed to areas near Lake Merritt where apartment towers, strip retail and big-box retail were developed. However, it appears that Eastlake may be in the early stages of economic transition. The neighborhood is located in the City of Oakland’s Central City East Redevelopment Area, in which infrastructure for development projects may be financed through tax-increment financing,Repair shop. Source: Ingrid Severson. 7 Urban Ecology, Clinton Park Plan, August 1999. 2-10
  21. 21. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N Sproviding a public incentive for private development. A multi-million dollarstreetscape improvement project was also initiated in 2002 for the businessdistrict on 12th Street and International Boulevard between 5th Avenue and 8thAvenue. Rehabilitation and new construction projects in Eastlake may pro-vide an opportunity to incorporate rooftop features into the neighborhood.IV. BUILDING TYPOLOGYBuildings in the Study Area are classified by type for the purposes of this as- “Big Box building. Source: Ingrid Severson.sessment. The typology categorizes flat-roofed buildings into eleven types toallow for generalized estimates of structural properties and roof loading ca-pacities. Buildings with pitched roofs are not included in the typology sincethey were assigned the rainwater harvesting and solar photovoltaic proto-types. Both systems are sufficiently lightweight to be installed on virtually allpitched roof buildings, regardless of the building type. To account for thepotential of future development in the area, vacant lots were identified as op-portunity sites in which new construction could plan for the inclusion ofrooftop systems. Table 2-1 describes the typical characteristics of each flat-roofed building type and associated roof loading capacities. Typical office building. Source: DC&E.In addition to assigning a building type to each flat-roofed structure, a fieldsurvey conducted by the consultants and Bay Localize volunteers recordeddiscrete characteristics such as occupancy type, height, construction type andera, and presence of a “soft story.” Estimates of loading capacity are refinedto account for differences in these factors when they do not match the typicalassumed characteristics of the building type.A. Building Type Distribution One of nine vacant lots identified as opportu-A wide variety of building types are found in the Study Area. Table 2-1 de- nity sites. Source: Ingrid Severson.scribes the building type split over the area. Table 2-2 illustrates the distribu-tion of building types in the area. 2-11
  22. 22. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TE X I S T I N G C O N D I T I O N STABLE 2-1 BUILDING TYPOLOGY-TYPICAL CHARACTERISTICS Additional Loading Occupied Construction Capacity*Building Type Land Use Stories Construction Material Era Size/Scale (psf)House Residential 1-2 Wood-framed Any Up to 4 units 20Apartment Building Residential 1-4 Wood-framed After 1950 4 to 10 units 15Apartment Tower Residential 5+ Concrete or Steel After 1980 More than 10 units 5-7 Retail/ VariesMixed Use 2-5 Wood framed Any Varies Residential (8-12)Shops Commercial 1 Wood-framed After 1970 Varies 17 Masonry or Concrete blockWarehouse Varies 1 walls, riveted steel or large- Prior to 1960 Large, open floor plan 5 timber columns Retail, Concrete block or tilt-up con-Big-Box 1 After 1960 Large, open floor plan 5 Industrial crete walls, interior steel posts Smaller, open floorRepair shop Commercial 1 Concrete block Any 7 plan, open storefrontOffice Building Office 2+ Varies After 1960 Varies 17 School, hospital, church, auditorium, library, thea- VariesCommunity Building 1+ Varies Varies Varies ter, police, fire, post office, (5-17) etc.* A removal of pea-gravel/rock ballast (secured on the roofs of any of these buildings) can increase the “dead-load” capacity by an average of 4-5 psf for every inch of ballast removed. 2-12
  23. 23. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T E X I S T I N G C O N D I T I O N STABLE 2-2 BUILDING TYPE DISTRIBUTION Number PercentageBuilding Type of Buildings of TotalHouse 20 2.7Apartment Building 160 21.3Apartment Tower 8 1.1 Community building. Source: Ingrid Severson.Mixed Use 36 4.8Shops 40 5.3Warehouse 14 1.9Big Box 7 0.9Repair Shop 6 0.9Office Building 7 0.9Community Building 30 4.0 Apartment building. Source: DC&E.Parking Garage 1 0.1Pitched Roof Building 419 56.01Total 748 99.91 Warehouse building. Source: Ingrid Severson. 2-13
  24. 24. BAY LOCALIZE ROOFTOP RESOURCES NEIGHBORHOOD ASSESSMENT E. 19th St. d. Blv rk Pa E. 18th St. E. 17th St. Lake Merritt Foothill Blvd. . Bl vd re E. 15th St. sh o 1st Ave. 2nd Ave. 3rd Ave. 4th Ave. e 5th Ave. 6th Ave. 7th Ave.Lak 8th Ave. International Blvd. Clinton Square Park E. 12th St. E. 11th St. E. 10th St. 0 250 500 Feet Figure 2-2. Aerial view of Study area House Big Box Repair Shop indicating distribution of Apartment Building Shops Opportunity Site building types. Apartment Tower Office Building Unknown Mixed Use Parking Garage Pitched Roof Community Center Warehouse Study Area
  25. 25. 3 ROOFTOP RESOURCE PROTOTYPES For the purposes of this assessment, five rooftop resource prototypes were developed. These prototypes provide assumed characteristics that can be ap- plied to each of the rooftop resource models, including weight and productiv- ity. This chapter describes the design concepts, architectural and maintenance requirements, and potential benefits of the five prototypes. It also analyzes the synergies and conflicts that could arise if the prototypes are implemented in concert. The rooftop resource prototypes are a set of design concepts that represent various strategies for rooftop utilization. The design process was informed by Raised vegetable garden on rooftop. Source: the objective of utilizing rooftops in a manner that is productive, sustainable, Resource Centres on Urban Agriculture and and feasible. In addition, the goal of assessing rooftop capacity on existing Food Security. buildings in their current condition—rather than on new construction or on structurally reinforced buildings—made loading a central consideration in the prototype design. Table 3-1, found at the end of the chapter, describes the components, cost ranges, and yields of the prototypes. The prototypes are necessarily generalized to allow for variations in roof size and type, roof slope, building type, wind variables, client budget, and other conditions. They should be taken as examples of possible configurations and should not be relied upon for specifications for any site. Before any specific rooftop resource is developed, professional consultation should be obtained to determine precise design loads and roof loading capacity. I. EXTENSIVE GREEN ROOF A. Design Concept Extensive green roofs are the most common type of green roof found today, valued for their many environmental benefits. The prototype follows the typical configuration of extensive green roofs in arid climates, in which low- growing, drought-tolerant ground cover is planted in 4 to 6 inches of growing substrate and placed on an assembly of filter fabric, a drainage layer, root 3-1
  26. 26. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E S TABLE 3-1 PROTOTYPE CHARACTERISTICS Annual Major Maximum Productive Prototype Components Weight Yield ½" Drainage Mat Extensive Green drainage and 4" Mineral Substrate 22 psf Roof energy benefits Sedums 2¼" Drainage Board Intensive Green 1.86 psf 18" Organic/Mineral Substrate 108 psf Roof—Vegetables vegetables Variety of Vegetable Crops 1 ¼" Drainage BoardExtensive green roof. Source: American Intensive Green 8" Organic/Mineral Substrate 51 psf perennial yieldHydrotech. Roof—Herbs Herbaceous Plants Growing Container Hydroponic Reservoir Container 4 psf 16 psf Rooftop Garden 4" Inert Substrate vegetables Variety of Vegetable Crops Solar Multicrystalline PV Panels 1 kilowatt per 5 psf Photovoltaics Mounting Hardware 100 square feet Conveyance-Gutters/Leaders average Debris Screen 3,000 ga. per Rainwater First-flush Diverter N/A structure Harvesting Roof Washer (1" rain on 100 sf Storage Tank/Cistern = 60 gal.) barrier, and a waterproof roof membrane. This type of assembly can be in- stalled directly on the roof or placed in trays that are installed as a modular system. Extensive green roofs differ from intensive green roofs in the mini- Extensive green roof assembly. Source: mal depth of the substrate and more limited planting possibilities. Figure 3-1 American Hydrotech. illustrates the prototype assembly and vegetation. 1. Green Roof Assembly The Extensive Green Roof prototype is intended to extend across the maxi- mum feasible area of the building to confer the greatest storm water and en- ergy benefits. Plants are established in four inches of substrate, considered a minimum depth for plants to endure dry Bay Area summers. In this case a 3-2
  27. 27. B AY L O C A L I Z E R o o f t o p R e s o u r c e s N e i g h b o r h o o d A s s e s s m e n tFigure 3-1. Cross-section of Extensive Green Roof prototype.
  28. 28. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E S blend with high mineral content and low organic content should be devel- oped to provide moisture and air retention while minimizing the load im- posed upon the roof. While the exact blend depends highly on the site, one very appropriate medium is pumice, which is one of the lightest mineral ma- terials mined within 500 miles of the Bay Area. Expanded shale is another very lightweight mineral that exists in California; however, it is currently shipped in from Colorado and other Western states, resulting in higher trans- portation costs and environmental impacts. Lava and scoria are available from the Clearlake area in Northern California, but they are heavier than pumice and expanded shale. Whichever mineral medium is selected should beExtensive green roof modular tray system.Source: Green Roof Blocks. combined with a minimal amount of organic material, such as locally- available compost. Beneath the substrate, a ½-inch thick recycled polyethylene drainage mat aer- ates and drains the media, and attached filter fabric prevents it from clogging the drainage layer. Finally, a root barrier and waterproof membrane protect the roof deck from the living layer above. A popular alternative to the type of assembly described above (which is built- up directly on the roof) is the modular approach, in which the above compo- nents are assembled in container trays and installed on the roof. Modular systems present a number of benefits. Perhaps their most notable benefit is“Green Paks” modular tray system. Source: the flexibility they allow in installation and removal. They can often be in-Green Roof Blocks. stalled without re-roofing, while the soil membrane system may require re- placement or major repair to the roof membrane. In addition, building own- ers may be more open to experimenting with a green roof installation know- ing that the trays can be easily removed if desired. Whether the soil membrane approach or the modular system is chosen for a particular roof, the described components of the extensive green roof assem- bly are almost identical in other respects. 3-4
  29. 29. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E S2. PlantsThe Extensive Green Roof prototype is planted with of a mix of regionally-appropriate sedums, such as Sedum album, Sedum spathuifolium, Sedum spu-rium, and Sedum sexangulare. The specific species chosen for a particularrooftop context depends on many factors, including: ♦ Initial budget and maintenance budget. ♦ Physical conditions, such as shading and wind. ♦ Roof slope. ♦ Retrofit schedule and seasonal variables.Planting methods can vary, from direct seeding in the growing medium dur-ing installation to application of pre-planted container trays or vegetatedmats. Generally, materials for vegetated mats and modular tray systems aremore expensive but labor costs are reduced, while seeding or transplantingplugs directly is more labor-intensive but reduces materials costs.B. Architectural RequirementsBecause extensive green roofs are a low-impact, low-maintenance rooftop re- Sedums on extensive green roofs using modularsource, they can be useful on buildings with a wide range of characteristics. systems. Source: Green Roof Blocks.Their implementation on existing buildings in the Bay Area is constrained,however, by their weight. The lightweight Extensive Green Roof prototypeweighs approximately 22 pounds/square foot (psf),1 precluding installation onmany building types. This weight value is at the low end of the spectrum forextensive green roofs.Because the prototype is not intended to be used as occupiable space, egressrequirements are more lenient than for rooftop gardens. Older stairways1 All green roof loading estimates are based on design loads from the German greenroof standard, “Guidelines for the Planning, Execution, and Upkeep of Green-roofSites,” published by FLL (Forschungsgesellschaft Landschaftsentwicklung Land-schaftsbau e.V.), 2002 Edition. 3-5
  30. 30. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TR O O F T O P R E S O U R C E P R O T O T Y P E Swith steeper inclines to the roof, or common ladder and hatch access, wouldboth be sufficient to provide necessary maintenance.C. Maintenance RequirementsExtensive green roofs are intended to be a low-maintenance technology. Dur-ing the first year after installation, plants need to be irrigated as they establishthemselves. Planting hardy, drought-resistant, regionally-appropriate varie-ties such as those specified in this prototype will limit irrigation needs overthe long-term since these plants are accustomed to the arid conditions of BayArea summers. However, minimizing substrate depths to the level entailed inthis prototype would likely require that some irrigation occur on a regularbasis, depending on the conditions of the site. The extensive green roof needsto be inspected only a few times a year to ensure that all components, includ-ing the membrane, are functioning as intended.Extensive green roofs can reduce roof maintenance demands and as much asdouble the life of the roof membrane by protecting it from extreme tempera-ture changes, ultraviolet radiation, and accidental damage.2D. Cost RangeThe extensive green roof prototype is a relatively low-cost rooftop resourcestrategy, though initial costs are higher than that of a conventional roof. De-pending on the type of labor that is used, accessibility and size of the roof,and the planting method, initial materials and labor costs are estimated at $152 City of Chicago, Design Guidelines for Green Roofs,http://egov.cityofchicago.org/webportal/COCWebPortal/COC_ATTACH/design_guidelines_for_green_roofs.pdf (accessed April 8, 2007).3-6
  31. 31. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E Sto $22 per square foot. This estimate assumes that the prototype is appliedwhen a new roof is needed and therefore excludes the cost of a new roofmembrane, which generally adds another $8 to $12 per square foot. Pre-planted trays with irrigation in place cost approximately $25 to $30.3In considering the financial viability of extensive green roofs, it is importantto note that they are more cost-competitive with conventional roofs whenusing a life-cycle costing approach, which incorporates savings from reducedmaintenance and longer roof life, as well as ongoing energy efficiency savings.Life-cycle costing is a valuable method for understanding the benefits of many“green” technologies, which may cost more initially but which may result incost savings over the operating life of the product.E. BenefitsWhile the extensive green roof prototype does not yield a harvest of food,energy, or water, it does confer a number of environmental and aestheticbenefits, including: ♦ Storm Water Retention. Extensive green roofs are valued for their storm water retention capacity and a good deal of research is being con- ducted to quantify these benefits. By capturing and holding water in the vegetation and substrate layers, the extensive prototype can mitigate flooding and combined sewer system backup (where applicable) in heavy rain events. This prototype can also improve the quality of runoff water by capturing and holding pollutants in the substrate. Studies indicate that an extensive green roof can absorb as much as 70 percent of rainfall3 All costs are derived from Steven Peck and Monica Kuhn, “Design Guidelines forGreen Roofs,” Ontario Association of Architects and Gabrielle Fladd, “Green RoofMatrix” (cost analysis paper presented in San Francisco Planning & Urban ResearchAssociation, Green Roof Task Force meeting, San Francisco, CA, June 2007). 3-7
  32. 32. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E S from a storm event, releasing the remainder over an extended period of time.4 ♦ Energy Efficiency. The extensive prototype can improve building per- formance, effectively acting as a heat trap, while also shading the roof and cooling the roof surface through evaporation and vegetative transpira- tion. A study in Canada found that when implemented broadly on a city or regional scale, extensive green roofs can significantly reduce ambient urban temperatures, thereby lowering energy demand for air condition- ing. The living roof on Chicago’s city hall building stands as a popular case study modeling the cooling effect of green roofs. It has been re-Intensive roof garden. Source: AmericanHydrotech. corded as 7 degrees cooler than surrounding roofs on an annual average, and up to 30 degrees cooler during the summer time.5 II. INTENSIVE GREEN ROOF-VEGETABLE GARDEN A. Design Concept The Intensive Green Roof—Vegetable Garden prototype is designed to sup- plement the environmental and aesthetic benefits of the extensive prototype with food production and an open space amenity. Vegetables would beIntensive green roof—vegetable garden. grown in 18 inches of growing medium, the minimum depth to support aSource: The Rooftop Garden Project,Alternatives, 2004. large variety of vegetables. The assembly of the prototype is similar to that of the extensive prototype, consisting of a water proof membrane, root barrier, drainage layer, filter fabric, substrate layer, and plants. Figure 3-2 provides a section of the green roof assembly. 4 ASLA et al., “Landscape Architects Release Green Roof Performance Report: Roof Retained 27,000 Gallons of Stormwater in First Year,” http://asla.org/press/2007/ release091907.html. 5 Karen Liu, “A National Research Council Canada Study Evaluates Green Roof Sys- tems’ Thermal Performances,” http://www.professionalroofing.net/article.aspx? A_ID=130 (accessed April 8, 2007). 3-8
  33. 33. B AY L O C A L I Z E R o o f t o p R e s o u r c e s N e i g h b o r h o o d A s s e s s m e n tF i g u r e 3 - 2 . C r o s s - s e c t i o n o f I n t e n s i v e G r e e n R o o f — Ve g e t a b l e s p r o t o t y p e .
  34. 34. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E S In this case, however, the vegetated roof is not intended to cover the entire roof area. Instead, paths are created by closing in growing areas with retain- ing walls, constructed of lightweight materials such as wood or recycled plas- tic. A protective surface would be installed to protect the roof from foot traf- fic damage. This arrangement provides accessible spaces similar to ground- level container gardens. While a multitude of different arrangements are pos- sible, depending on the existence of fixed obstructions on the roof, it is esti- mated that this prototype would provide an average growing area of 60 per- cent of total roof area. This estimate takes into account space unavailable due to fixed obstructions as well as space needed for paths and equipment storage.Crop Variations 1. Green Roof AssemblyA wide variety of vegetables may The prototype includes 18 inches of substrate, in this case a blend of aboutbe suitable for rooftop environ- equal parts mineral and organic content. Conventional topsoil and pottingments in the East Bay, despite soil are inappropriate media for rooftop environments, particularly on exist-such challenges as wind, heat, and ing buildings, due to their weight. Instead, the medium used in this proto-evaporation. Experimentation is type would include approximately equal parts organic material, such as com-needed to better establish planting post or bark humus, and mineral material such as pumice or scoria. Thepossibilities. While the prototype drainage layer in this prototype is a 2¼ inch thick recycled polystyrene drain-suggests several popular garden age board. The drainage course is filled with lava or similar mineral materialvegetables, other appropriate for structure. Other components are similar to the extensive green roof pro-edible crops may also include totype.broccoli, celery, chard, collards,eggplant, kale, mustard, green 2. Plantsonions, and peppers. In addition, The prototype is designed to provide year-round vegetables that could thrivesome of these crops may be in the Bay Area. A selection of vegetables was developed based on severalplanted in less than 18 inches of criteria, including:growing media, which was used ♦ Regional suitabilityin this prototype as a conservative ♦ Growing medium depth requirementsvalue for growing a large varietyof edible plants in potentially ♦ Plant weight at maturity (structural consideration)harsh conditions. ♦ Height at maturity (wind loading considerations) ♦ Full sun tolerance ♦ Normal to low water needs ♦ Growing season 3-10
  35. 35. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E SBased on these criteria, plants were selected that could be rotated to grow ona year-round basis. Cool-season crops in the prototype are spinach, mustard,carrots, and beets. Tomatoes, cucumbers, and winter squash are included aswarm-season crops, along with leaf lettuce, which in many cases can be grownyear round. Variations on this arrangement should provide an opportunityto grow cool-season crops twice yearly—planted in the early Spring and Fall—while planting warm-season crops in late Spring. Additional crops that couldbe grown on this prototype are listed in the side box.B. Architectural RequirementsThe vegetable garden prototype would introduce a new roof load of ap-proximately 108 psf to the structure.6 Providing this type of structural sup- Intensive green roof assembly. Source:port would require a uniquely-tailored structural design incorporated into American Hydrotech.new construction. As an occupiable space, the vegetable garden prototypewould require a code-compliant stairway or elevator, as well as guardrails orfencing around the roof edge.C. Maintenance RequirementsThe prototype would require substantial maintenance, much of which is as-sociated with normal vegetable gardening activities. Maintenance demandswould include regular irrigation, pruning, weeding, fertilizing, and pest con-trol. Water needs could be increased relative to ground-level gardening due tohigher rates of heat- and wind-induced evaporation. Depending on budget,irrigation could take place through hand-watering or sub-surface drip irriga-tion, the latter of which would reduce water use and labor requirements. In6 All green roof loading estimates are based on material design loads in the Germangreen roof standard, “Guidelines for the Planning, Execution, and Upkeep of Green-roof Sites,” published by FLL (Forschungsgesellschaft Landschaftsentwicklung Land-schaftsbau e.V.), 2002 edition. 3-11
  36. 36. B A Y L O C A L I Z ET A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P SR O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N TR O O F T O P R E S O U R C E P R O T O T Y P E Saddition to regular maintenance of the growing area, inspection and repair ofthe roof membrane would be required on an occasional basis.D. Cost RangeInitial costs depend greatly on the type of labor that is used, accessibility ofthe roof, and planting method, as well as the size of the roof. Given thesevariables, it is estimated that materials and labor costs to install this prototypewould range from $30 to $45 per square foot of growing area, plus an addi-tional $20 to $40 per linear foot for guardrails and an optional $2 to $4 persquare foot if irrigation is installed.7 This estimate assumes that the prototypeis applied when re-roofing is needed and therefore excludes the cost of a newroof membrane. It also assumes that structural and architectural require-ments of the Building Code are already satisfied.E. BenefitsIn addition to providing storm water retention and treatment, energy effi-ciency and aesthetic benefits, this prototype provides an open-space amenityto building residents. Food production on the roof also results in a numberof valuable outcomes, such as new wildlife habitat, recreational and educa-tional opportunities, and readily accessible fresh, healthy produce. Ade-quately maintained year-round, this prototype would yield approximately1.86 pounds of vegetables per square foot annually.87 Stephen Peck and Monica Kuhn, “Design Guidelines for Green Roofs,”http://egov.cityofchicago.org/webportal/COCWebPortal/COC_ATTACH/design_guidelines_for_green_roofs.pdf (accessed March 24, 2007).8 Nancy Garrison, “Home Vegetable Gardening,” University of California Coopera-tive Extension, http://vric.ucdavis.edu/veginfo/veginfor.htm. This figure is an aver-age of vegetables’ approximate yields, multiplied by three seasons.3-12
  37. 37. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E SImplemented on a broader scale, this type of green roof can improve localfood security and reduce “food miles traveled,” thereby reducing the energyand climate impacts of food transportation. A study conducted in 2001 atIowa State found that in the conventional American agriculture system, foodtravels an average of 1,500 miles from its origin to its point of consumption.9III. INTENSIVE GREEN ROOF—HERB GARDENA. Design ConceptThe concept of this prototype is largely similar to the Vegetable Garden pro-totype, except that herbs are grown instead of the wider variety of vegetables. Intensive roof garden atop the Fairmont RoyalPlants included are rosemary, thyme, and cilantro. The growing medium York Hotel in Toronto grows vegetables,remains the same—a lightweight, soil-free mix of approximately equal parts herbs, and edible flowers. Source: Lorraineorganic and mineral material—but substrate depth is reduced to 8 inches, a Flanigan.minimum for many herbs that would be suitable for a rooftop environment.The drainage layer is also similar to the Vegetable Garden prototype, but itsthickness is reduced to 1¼ inches. Figure 3-3 illustrates the green roof assem-bly and vegetation.B. Architectural RequirementsAn approximate load of 51 psf would result from installation of this proto-type.10 As an accessible garden, this prototype would be considered an occu-piable space, subject to code requirements for stairways and guardrails.9 Leopold Center for Sustainable Agriculture, Food, Fuel and Freeways, An Iowa Per-spective on How Far Food Travels, Fuel Usage, and Greenhouse Gas Emissions, June2001.10 All green roof loading estimates are based on the German green roof standard,“Guidelines for the Planning, Execution, and Upkeep of Green-roof Sites,” publishedby FLL (Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V.), 2002edition. 3-13
  38. 38. B AY L O C A L I Z E R o o f t o p R e s o u r c e s N e i g h b o r h o o d A s s e s s m e n tFigure 3-3. Cross-section of Intensive Green Roof—Herbs prototype.
  39. 39. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E SC. Maintenance RequirementsMaintenance needs would be significant and would include regular irrigation,pruning, weeding, fertilizing, and pest control. Irrigation needs would bereduced compared to the Vegetable Garden prototype, but a sub-surface dripirrigation system would still be desirable. As with all green roofs, regularinspection of the roof membrane would be required, and occasional repair ofthe membrane could prove necessary.D. Cost RangeGiven the cost variability factors that apply to all green roofs, it is estimatedthat materials and labor costs for this prototype would range between $28 to$40 per square foot, plus an additional $20 to $40 per linear foot for guardrailsand an optional $2 to $4 per square foot if irrigation is installed.11E. BenefitsIn addition to the environmental and social benefits previously noted, thisprototype would provide an ongoing supply of culinary herbs.11 Stephen Peck and Monica Kuhn, “Design Guidelines for Green Roofs,”http://egov.cityofchicago.org/webportal/COCWebPortal/COC_ATTACH/design_guidelines_for_green_roofs.pdf (accessed March 24, 2007). This estimate as-sumes that the prototype is applied when re-roofing is needed and therefore excludesthe cost of a new roof membrane. It also assumes that structural and architecturalrequirements of the Building Code are already satisfied. 3-15
  40. 40. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E S IV. HYDROPONIC VEGETABLE GARDEN Hydroponics, also known as ‘organoponics’ in Latin America, is a horticul- tural method that supplies plant roots with liquid nutrients, eliminating the need for organic material that provides nutrients under conventional meth- ods. Plants are provided with nutrient solution, and are either grown in an inert mineral substrate or are suspended above the solution without substrate. The hydroponic model substantially reduces the weight of vegetable cropping systems by eliminating the growing medium. No fewer than six different techniques can be used to operate the system, some of which involve such equipment as water pumps, air pumps, comput-Commercial hydroponics. Source: Aaron erized monitors, timers, and lighting, when used indoors. This model of hy-Lehmer. droponics does not require artificial lighting as there is adequate sunlight for growing plants on the roof. The water supply is plumbed from the building to feed into the hydroponic system. A unique design component of the roof- top hydroponic prototype is a shade-cloth or light screen meshing as a ‘lid’ to protect the growing medium from being blown away in the wind. This re- taining cloth may be stapled along the edges of the container trays. A. Design Concept The Hydroponic Rooftop Vegetable Garden prototype utilizes a low-tech, low-cost method that minimizes weight while maximizing vegetable produc- tivity, variously called Simplified Hydroponics or Popular Hydroponic Gar- dens (PHG). The design is based on concepts developed and implemented around the world by the UN Food and Agriculture Organization (FAO), the UN Development Program (UNDP), and the Institute for Simplified Hydro- Rooftop hydroponics. Source: The ponics. Rooftop Garden Project, Alternatives, 2004. In this prototype, containers are filled with lightweight mineral substrate to a depth of 4 inches. Perlite is used as a base, and combined with inert organic material such as rice hulls, peanut hulls, grain chaff or coconut coir. The ad- 3-16
  41. 41. B A Y L O C A L I Z E T A P P I N G T H E P O T E N T I A L O F U R B A N R O O F T O P S R O O F T O P R E S O U R C E S N E I G H B O R H O O D A S S E S S M E N T R O O F T O P R E S O U R C E P R O T O T Y P E Sdition of these organic materials provides a more balanced substrate, thus fos-tering a healthier medium for the plants. This growing medium is ideal for itsextremely low weight, but it should be noted that other lightweight basescould be used, such as pumice. Appropriate plants include cooking and saladgreens, most summer and winter vegetables and herbs. Root vegetables canbe grown hydroponically but require greater substrate depths than specifiedin the prototype. Planting methods may vary among vegetable types, butgenerally seedlings are transplanted into the substrate, where they have regu-lar access to the nutrient solution.The prototype utilizes the “flood and drain” method of hydroponics, inwhich the nutrient solution is circulated back and forth between the growingcontainer and a reservoir container. The growing container is constructedwith a drain approximately one inch above the base, allowing for some accu-mulation of solution in the bottom of the container but draining the remain-der. If the growing container is elevated and placed at a minimal slope, drain-age can be gravity-fed. Alternatively, a pump can be used to continually floodand drain the growing container, recirculating the nutrient solution.Accounting for roof obstructions, pathways and storage areas, it is assumedthat growing area would constitute 60 percent of the total roof area. Figure3-4 illustrates the components of the prototype.B. Architectural RequirementsUnder normal conditions, the prototype would add approximately 9 psf tothe roof load. However, in a heavy rain event, the substrate may be saturatedand an inch of water could accumulate in the bottom of the growing con-tainer, resulting in a maximum load of approximately 16 psf.This prototype would be considered an occupiable space, subject to code re-quirements for access and guardrails. 3-17
  42. 42. B AY L O C A L I Z E R o o f t o p R e s o u r c e s N e i g h b o r h o o d A s s e s s m e n tFigure 3-4. Cross-section of Rooftop Hydroponic Garden prototype. Source: Based on designs in Bradley and Marulanda 2000

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