Should Denver require rooftop gardens to reduce heat island effect? Voters might decide this year

Proposed initiative for large buildings could go on November ballot, but it likely faces fight from developers.

Denver’s status as one of the nation’s most intense urban heat islands has spurred a group of activists to propose a “green roofs” ballot initiative — a measure that could animate environmentalists while mobilizing developers to fight it.

But the people behind the initiative, which would require gardens atop most new buildings of at least 25,000 square feet, also were motivated by a more recent factor: the election of Donald Trump as president.

“I’m very passionate about climate change, and with our recent election, it’s time for our citizens to take the initiative and battle some of the climate changes we are experiencing,” said Madison Backens, a biology student at the University of Colorado Denver. She has taken on the role of primary sponsor.

“Because our government isn’t really supporting that right now,” she added, referring to Trump’s public skepticism toward the scientific consensus on human-caused climate change.

The group of activists skews young — Backens is 22, and campaign manager Brandon Rietheimer is 30 — but their effort is being taken seriously by city attorneys, an urban horticulture expert, and skeptical developers of apartments and office buildings.

Rules would be among most stringent in U.S.

If approved by voters in the Nov. 7 election, the new local building code requirements sought by the backers would be among the strongest in the United States. The measure would follow the lead of San Francisco, which in December adopted an ordinance that forces developers of certain buildings to incorporate solar panels or roof gardens.

But Denver’s measure isn’t assured of making the ballot yet. The Denver Elections Division has approved the initiative for petition-gathering, and now proponents have nearly six months to collect more than 4,700 valid signatures from registered Denver voters.

Backens said more than 30 people turned out for the Denver Green Roofs Initiative’s kickoff gathering Thursday night

How green roofs can help

In large cities, heat-radiating roofs and pavement often elevate temperatures several degrees in the summer heat. A 2014 analysis by Climate Central, a scientific advocacy group, found that semi-arid Denver’s average daily summertime temperature during the previous 10 years was 4.9 degrees higher than in nearby rural areas; it recorded the third-largest “heat island” effect among U.S. cities, behind Las Vegas and Albuquerque.

Advocates of green roofs — also called “living roofs” — say the increased vegetation reduces that heat effect, results in less storm-water runoff and also helps fight air pollution.

Rietheimer says he looks to Toronto as a model, since it became the first North American city to approve a green-roof requirement in 2010. He also researched building standards for rooftop gardens and added proposed structural guidelines to the proposed initiative.

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