Binding Green Roof regulations in new land-use plans, zoning codes or by-laws provide the highest impact level for the installation of Green Roofs in urban areas. In Germany for example binding Green Roof regulations have been applied by a large number of municipalities for more than 30 years. This instrument provides the backbone of the successful development of the German Green Roof market. However the application and acceptance of binding regulations is connected with the tradition of political intervention in the building sector and can differ from country to country.

Non-binding Green Roof regulations or performance standards provide the developer with the opportunity to use Green Roof installations in order to reach a specific environmental objective or performance target (e.g. stormwater retention, green building requirements or rooftop reflectance values). However the investor can also use other environmental technologies to meet the benchmark values. Because of the exchangeability with other technologies non-binding regulations will have a lower impact on the overall installation of Green Roofs. In general binding and non-binding regulations are used mainly for new developments.

Binding Green Roof Regulations

Land-Use Plan or Zoning Code: The land-use plan or zoning code establishes binding regulations for the development of a building site. Land use plans and codes can specify the category of use (residential, commercial, industrial, institutional or mixed), lot coverage, Floor Area Ratio, building height and other things. In addition, they can also mandate environmental measures like Green Roofs to compensate for the negative impact construction has on the site’s ecology. The installation of Green Roofs can be made mandatory for the whole roof or a percentage of the roof area. Exceptions are possible in justified cases. The ecosystem services of Green Roofs with regard to the climate, air, soil, water, flora, fauna, and landscape are undisputed. Many local authorities have incorporated Green Roof requirements in land-use plans or zoning codes for new building construction that requires planning approval. The regulations concerning Green Roofs should not only be applied to current construction projects but also to urban planning zones in which development will happen in the future. The aim of long-term Green Roof regulations is to guarantee that local authorities continue to develop their ecological concept in subsequent years.

Green Roof Bylaws: Another way of binding regulations are Green Roof Bylaws. In contrast to land-use plans or zoning codes Green Roof Bylaws address not only specific building sites but can make Green Roofs mandatory for all new buildings of a certain type throughout the city. The application of Green Roof Bylaws can depend on a minimum size of the roof area, the roof slope (e.g. slope of up to 20°) and the category of use of the new building (residential, commercial, industrial, institutional). The development of a Green Roof Bylaw is a time-consuming process that requires a lot of persuasion within the administration and city council. But once the bylaw is established it will have an enormous effect on the installation of Green Roofs. The list of cities that uses this kind of regulation includes Toronto (Canada), Copenhagen (Denmark), Tokyo (Japan) and Munich (Germany).

Green Roof Guidelines: The development of Green Roof guidelines will usually take place at the national level. These guidelines should contain basic information about the proper planning, installation and maintenance of Green Roofs in addition to material specifications. However, the development of an additional municipal Green Roof guideline can be useful if specific ecological performance values (e.g. water retention capacity, growing medium thickness or biodiversity) are needed to fix a local environmental problem. The national and municipal Green Roof guidelines need to be aligned in order to avoid confusion among the investors and developers.

Federal Building Codes: Federal building codes specify the requirements for the construction and occupancy of buildings and structures. Apart from safety aspects they can also address public health, environmental protection and facilitate the use of green technologies. In Germany the Federal Building Code describes the scope, definition and principles of urban land use planning and the content of the land-use plan. Therefore it is very important that the German Federal Building Code already contains a section which enables municipalities to make Green Roofs mandatory in new land-use plans.

Non Binding Green Roof Regulations

Stormwater Management Requirements: Nowadays stormwater management or water pollution prevention programs often address the use of best management practices (BMP) in order to control and treat stormwater on site and avoid combined sewer overflows. These practices can also include the installation of Green Roofs. The U.S. Environmental Protection Agency (EPA) for example has recognized Green Roofs as innovative BMP for stormwater management. The benefits of Green Roofs for stormwater management targets include the reduction of peak flow, less discharge of pollutants, and the storage and later evapotranspiration of stormwater. The stormwater management requirements can be set at a municipal, district or national level.

Green Building Certification: A number of Green Building Certificates encourage Green Roof installation within the frame of the certification process. The Leadership in Energy and Environmental Design (LEED) certificate offers credits for Green Roofs in different categories (e.g. sustainable site, water efficiency, energy and optimization, material and resources). Other Green Building labels like the Building Research Establishment’s Environmental Assessment Method (BREEAM) or the certification system of the German Sustainable Building Council (DGNB) also grant credits for Green Roofs. One of the benefits of this instrument is that Green Building requirements are set at a national or even at an international level.

Green Factor Program: The goal of the green factor program is to secure “green qualities” and ecosystem services in highly concentrated city districts. For this purpose the municipal authorities define a ratio for the ecologically effective surface area to the total land area of the new development. In this calculation, the different “surfaces” of a building project (land, wall, roof) are weighted with an "ecological value" (related to stormwater retention, habitat creation etc.). In order to reach the ratio, the developer has the freedom to choose between different environmental measures like semi-open surfaces on ground level, façade greenery or Green Roofs. The Green Factor program is also known as Biotope Area Factor (BAF) and used in Berlin (Germany), Malmö (Sweden) and Seattle (U.S.). It can be integrated in land-use plans or zoning codes instead of binding Green Roof regulations.

Cool Roof Requirements: The roof can play an important role in a building’s energy balance, climate change mitigation, and Urban Heat Island reduction. Some municipalities are therefore using cool roof requirements for solar reflectance and thermal emittance to make the roofscape of the cities more energy efficient. Apart from high reflective white roofs and insulated cool roofs also Green Roofs can be used to meet these requirements. Again it should be considered that a cool roof only addresses energy, but Green Roofs will provide an ecologically functional roof cover that provides many environmental and human health benefits.