A group in Denver want rooftop gardens to be on the ballot in November, according to Denverite.
The story says that the green roof requirements would start with buildings of 25,000 square feet. Buildings as large as 49,999 square feet would have gardens on 20 percent of the roof and buildings from 50,000 square feet and 99,999 square feet would have 30 percent coverage. The requirements would top out at buildings of 200,000 square feet, which would have to devote a minimum of 60 percent of their roofs to green gardens.
The story says that the rules would cover newbuilds, major additions to existing structures and new roofs.
Green Roofs for Healthy Cities provides a comprehensive list of benefits claimed for this approach. They include pure aesthetics, landfill diversion, storm water management, improved air quality and usefulness to the communities in which they are in.
Of course, a main set of benefits are related to energy. The site says green roofs moderate the urban heat island effect. Three points are raised: Plants naturally cool cities; the gardens in some cases cover black roofing (which generate the most internal building heat and drive up air conditioner use) and the gardens reduce distribution of dust and particles, which are associated with higher levels of greenhouse gases.
In response to emailed questions from Energy Manager Today, Steven Peck, the Founder and President of Green Roofs for Healthy Cities, echoed the idea that there are many attractive elements to green roofs. “The industry is being driven by policies supporting green buildings and green roofs on new and existing buildings; and because green roofs deliver benefits directly to building owners in terms of lower energy costs, higher property values, and extended waterproofing life expectancy, to name a few.”
People are listening, he wrote. “In North America, [green roofs] grew 18.5% between 2014 and 2015 with Washington, DC installing more than any jurisdiction. We are collecting statistics for 2016 and will have a report out in March.
This week, Lawn & Landscape reported on a green rooftop installation atop the Dell Medical School at the University of Texas. The story said that BrightView Landscape Development, Hensel Phelps Construction, Sasaki Associates and the Lady Bird Window Wildflower Center partnered to installed a 17,000 square foot roof on the building.
The green roof is made up of 7,000 individual plants, 500 cubic yards of lightweight soil, and a gravel perimeter for drainage. BrightView’s team assembled 600-pound sections of pre-cast curbing to create raised beds with varying depths to accommodate plants with larger root systems. These beds and materials were hoisted by crane and a custom tractor lift attachment was used to move materials on the roof.
The story says that the garden has sensors that will be used to assess materials and methods used in the project.
Research, Peck said, is ongoing. “Many manufacturers are working to develop and refine systems that improve their water holding capacity and reduce their weight.”