Earlier this month, Denver joined San Francisco as one of the first cities in the United States to mandate green roofs on new buildings. Beginning next year, 20 percent of rooftop space for newly constructed buildings must be covered by gardens or solar panels. The mandate applies to all new structures over 25,000 square feet, as well as roof replacements on existing buildings that meet the size threshold. Residential buildings with fewer than four stories are exempt.
“Green roofs improve the livability of cities by bringing nature and green space back into the urban environment,” says Jennifer Bousselot, a faculty member in the Department of Horticulture and Landscape Architecture at Colorado State University. “Green roofs function as ecosystems on top of buildings ... Their benefits are many, but are primarily related to managing and filtering stormwater, moderating urban temperatures, acting as filters to improve air quality, and providing habitat for pollinators and beauty for anyone that overlooks them."