By Carla Jones

Green infrastructure in cities is not a novel concept, but implementing policies to require green infrastructure in the United States is. In 2007, Seattle, Washington, was the first city in the United States to implement Green Factor, green infrastructure standards modeled after policies developed in Berlin, Germany, and Malmo, Sweden.

According to the city of Seattle, “the Green Factor is a landscape requirement designed to increase the quantity and quality of planted areas in Seattle while allowing flexibility for developers and designers to meet development standards.” Green Factor accomplishes this by tallying points on a score sheet. The point system promotes permeable paving, green roofs, vegetated walls, preservation of existing trees, and layers of vegetation along streets and other areas visible to the public.

Green Factor was first adopted as part of the Neighborhood Business District and is intended to advance the city’s growth management strategy. There are two basic requirements of Green Factor. The first is that the parcel must be in a commercial zone and the second is that a score sheet reflecting a score of at least .300 be submitted with the permit application.

The score sheet follows a simple equation of totaling all of the landscape features together for the parcel and then dividing that number by the parcel size to determine the “approximate percent landscaped area.” The weight of each landscape feature is determined by relative aesthetic and functional values that was developed by “best available science and professional judgement.” Developers are required to maintain a score or at least .300 or 30% of the project’s parcel area. This value is considered the project’s “green factor.”

The 3 top priorities for the Green Factor standards have been Livability, Ecosystem Services, and Climate Change Adaptation.

  • Livability: Former landscape requirements were intended to increase the aesthetics of the city. Green Factor aims to improve aesthetics while also improving the quality of life through human-scale spaces.
  • Ecosystem Services: Another goal is that these spaces be utilitarian. In addition to aesthetics, the landscaping must assist in managing stormwater, improving air quality, and providing habitat for birds and insects.
  • Climate Change Adaptation: One of the primary goals of Green Factor is to prepare Seattle for climate change by making it a resilient city.

By implementing Green Factor standards, cities can create beautiful spaces, improve air quality, create habitat for wildlife, reduce stormwater runoff, and serve as a buffer to waterways. Cities across the United States are now turning to Seattle for advice on developing their own Green Factor standards. Standards, like those of Green Factor, are important tools that can be used to serve as green infrastructure and bring nature into the city. These standards are just one way that a city can work towards being a biophilic city.

Carla Jones, Researcher for Biophilic Cities Project.  

Carla is a masters degree candidate for the Urban and Environmental Planning and Public Health disciplines at the University of Virginia. She is also the coordinator for UVA Architecture School’s Center for Design and Health