Reviving the World Wonder: Why Rooftop Gardens Should Cover Urban Landscapes

I. INTRODUCTION Garden rooftops have existed since ancient Babylonian times. (1) Presently, concerns about the environmental and economic costs of energy use in buildings and cities have led to renewed interest in the potential of such gardens by local, state, and federal governments. (2) In the past decade, for example, Chicago has commenced the design or construction of more than 600 public and private green roofs. (3) The city is especially known for the 20,000 square foot garden crowning its eleven-story City Hall. (4) Of the roughly 770 green roof projects currently under way in the United States--which cover approximately 10.3 million square feet in total--two million square feet, or 19%, belong to Chicago. (5) Chicago is not the only city embracing the idea that there is finally a technologically feasible way to have both a high-rise and a sunny park. (6) Washington D.C. and New York City are also actively promoting rooftop gardens. (7) Today, the public sector has served as the main stimulant of green roof development in these cities through tax incentives, grants, direct procurement, research, and regulations. (8) For example, in 2005 Chicago offered twenty $5,000 grants to encourage homeowners and small businesses to install green roofs. (9) The city also granted $400,000 to Schwab Rehab Hospital to convert its roof into a 10,000 square foot garden. (10) Moreover, international cities have enacted green-roof mandates for the private sector as well. Toronto, Ontario, Canada became the first city in North America to mandate green roofs on private buildings in May 2009 when city legislature passed a by-law which requires green roofs for all new developments. (11) Berlin and Tokyo have also developed mandatory green roof laws. (12) The proposal that follows in this Note, therefore, has a number of successful international models and precedents. (13) This Note will first describe green roof technology, including the varieties of design. Second, the Note will address the environmental and cost-saving benefits of green roofs. A discussion of current public green building initiatives in the United States will follow, including a case study of Newark, New Jersey. Next, the Note will provide examples of green roof initiatives internationally and analyze the legal implications were mandatory green roof legislation adopted in the United States. The author concludes that courts will likely not oppose green roof mandates, and that private developers are likely to comply with such laws. Meaningful environmental and economic impact from urban green roofs can only be accomplished through large-scale implementation, (14) facilitated by progressive zoning regulations. II. GREEN ROOF TECHNOLOGY Green roofs are simply roofs bearing vegetation.... (15) To grow a roof-top garden, there are essentially two approaches to layering the growing medium, diversifying vegetation, and installing irrigation on a green roof: intensive and extensive. (16) An intensive roof is designed with an aesthetic and recreational purpose in addition to the functional benefits. (17) An intensive green roof has a deep substrate, hosts a variety of flora, and requires significant investment for set up and continued maintenance. (18) By contrast, an extensive garden is designed almost exclusively for its functional benefits, such as thermal insulation, fireproofing, and storm-water management. (19) These benefits can be accomplished with a less elaborate plant core, shallower soil, and low-growing vegetation. (20) The basic structure of an extensive garden includes a layer of insulation material and a waterproofing membrane, topped by soil and vegetation. (21) Intensive roof design typically requires the following enhancements to the basic structure: (1) about sixty to two hundred pounds per square foot additional structural support; (2) a minimum of eight inches soil depth, compared to the eight-inch maximum for extensive gardens; (3) widespread plant variety, constrained only by the climate, degree of exposure, substrate depth, and irrigation capacity of the garden, by contrast to the height and weight limits imposed on vegetation in extensive gardens; (4) irrigation systems and maintenance services, compared to the almost no-maintenance nature of extensive gardens. …

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