The Denver City Council unanimously voted to repeal and replace its green roof law, which was approved in 2017, that required rooftop greenery on buildings larger than 25,000 square feet, according to www.constructiondive.com.
The revised law instead requires light-colored, reflective "cool roofs," and developers can choose one of several new options for meeting environmental goals: build green space into the structure or lot; pay a per-square-foot fee to fund green space or energy-efficiency somewhere else; or implement renewable energy or meet standards for an environmental certification program, such as LEED.
The law changes will affect new construction and reroofing projects on buildings more than 25,000 square feet. The regulations are expected to be more cost-effective and achieve a broader array of environmental goals.
Real estate developers fought vigorously against the original green roof law, indicating it could have added nearly 3 percent to the cost of constructing large buildings. Research also indicates many existing Denver roofs could not handle the extra weight of adding greenery under the new law.
Under the new law, developers and building owners still will have to pay more than when creating a traditional roof, but the costs are expected to be significantly less than the original law—20 percent to 90 percent less, depending on the structure, with an average of 50 percent savings.
Although vegetative roofs offer numerous benefits, cool roofs also can be effective with urban heat island mitigation. Incorporating enough light-colored, reflective roofs reportedly can contribute to lowering an urban area's temperature by several degrees.