ULI Colorado Blog

Rooting out Denver’s new green roof law

by Michael Leccese

On November 7, 2018, ULI Colorado presented a case study and panel of experts looking at Denver’s new Green Building Ordinance, which came out of a November 2017 public vote to require green roofs on all commercial buildings.

A task force worked for months on translating the vote into a policy proposal, which Denver City Council adopted in late October.

An audience of 170 participated in the program while looking out at one of the city’s newest green roofs at the Flight office building at TAXI.

Originally opposed by many in the real estate industry as unworkable in Denver’s dry, windy climate, the final ordinance creates compromises that many experts seem to believe are more workable. The final law allows developers and building owner/managers (as the ordinance also covers replacement roofs) eight options, including solar, partial “green roof” coverage and underwriting other green spaces off-site.

No one doubts the need, though: Denver claims the third-worst urban heat island effect in the nation.

The program began with a case study imported from the Javits convention center in New York City. Kenneth Sanchez and Rebecca Marshall of the Javits Center discussed the installation of a 6.75-acre green roof in 2014 (part of a $463 million building overall). Mostly planted with hardy sedum groundcover, the roof requires minimal irrigation and support 26 bird species (including 100+ bird nests) and a honeybee colony that produces Javits-branded honey.

From a financial standpoint, the green roof contributes to a 26 percent reduction in energy use and it makes the building more resilient. In 2012, the Javits Center flooded during Superstorm Sandy. The roof is designed to detain 7 million gallons of water a year. When the center is expanded, the green roof will also be enlarged to include an intensive farm projected to produce 40,000 pounds of produce a year.

Next Katrina Managan, the city’s Energy Efficient Buildings lead, gave an overview of the new ordinance. Josh Radoff of WSP moderated a response panel.

Angela Loder of the New York-based International WELL Building Institute, advocated for the health benefits of green roofs. But to benefit people, green roofs need physical and visual access and more complex designs than a mat of sedum. She also called for (where practical) more complex, gardenesque planting schemes and play spaces on roofs.

Greg Dorolek, principal of Wenk Associates is a landscape architect who has designed several green roofs. Yet he said his office was split over support of the 2017 ballot issue. He emphasized stormwater quality improvements as a primary benefit and wondered if the final ordinance gave too many easy outs.

Ryan Bonner, president of Vertix built the green roof at the program host site, the Flight office building at TAXI. He stressed the importance of understanding green roof materials and working with a qualified contractor.

Jeannie Renee-Malone, VP of sustainability for ProLogis, served on the city Task Force to shape the law. ProLogis is the largest owner of industrial real estate with 3,700 buildings in 19 countries, including almost 7 million square feet in Denver. “The Denver ordinance caused an uproar in our office, but I was excited…my colleagues were worried that existing roof structures could not sustain the weight of green roofs.” Renee-Malone said that’s why the task force devised flexible compliance with the eight options.”

Eliot Abel, founder of Abel Clean Energy Advisors, believes that green roofs will prove their financial worth with increased value to investors, developers and property managers. He cited the example of a retrofitted warehouse at 5735 Arapahoe Avenue in Boulder. After an energy retrofit that included rooftop solar, the building’s cash flow increased $368,000 a year with an asset value increase of $560,000.

A lively audience Q&A session included a comment by Tim McManus of McManus Industrial that the ordinance would push Denver development to adjacent counties.

The program was sponsored by Lever Capital, Wenk Associates and Zeppelin Development, with community partners the Associated General Contractors of Colorado and U.S. Green Building Council.

The ULI Colorado Explorer series committee is co-chaired by Susan Brown of Valerian and Brandi Fuller of OZ Architecture. Committee planners included John Binder of KEPHART, Jocelyn Hittle of CSU/NWSS, Nate Jenkins of OZ Architecture, Laurinda Frederick of Greenberg Traurig, and Stevie Reynolds of MDP Engineering.

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