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The Mordecai Children's Garden is seen at the Denver Botanic Gardens on Wednesday, Sept. 29, 2021. (Olivia Sun, The Colorado Sun)

Jennifer Bousselot is nearly giddy about how her daily life as a Colorado State University horticulturist will change sometime in 2022, when rooftop green space in north Denver is finally at her disposal. 

Bousselot has helped design some of the most alluring features of CSU’s nearly-finished Spur campus at the National Western Center: rooftop greenhouses; beehives and gardens on the roof to study urban pollinators; irrigation experiments to see what plants need on an arid, scorching rooftop plain; and a stormwater study to see how much torrential rain a roof garden can slow down. 

“My favorite thing about green roofs,” Bousselot said, “is being able to bring a little piece of nature into our cities, where most people live.”

But while Bousselot has spent years helping get the concept of green buildings written into Denver law, the enchanting green elements of the CSU Spur campus happened without the help of any ordinance. As a university campus, Spur was exempt from the green building rules Denver passed in 2018

Denver officials and supporters of the 2018 rules, including Bousselot, who was a technical advisor to the planning committee, point to dozens of buildings with renovations approved under the program. They count at least 65 so far in buildings of at least 25,000 square feet, the minimum at which the rules kick in. 

“It’s a very good ordinance. I think it definitely has had an impact,” said Grace Rink, executive director of Denver’s Office of Climate Action, Sustainability and Resilience

While their enthusiasm for the push to green hasn’t waned, supporters acknowledge the green buildings ordinance, originally passed by Denver voters in 2017 as a “green roofs” law, hasn’t turned Denver into the kind of modern Hanging Gardens of Babylon some citizens hoped for. Denver officials rewrote the citizen-passed initiative through 2018 in order to give builders more options to comply. Nearly all the projects counted by the program’s annual report have taken the “energy efficiency” option for compliance, meaning a lot fewer rooftop gardens and a lot more invisible, stodgy solutions, such as triple-pane windows or heat pumps.

The Denver Botanic Gardens have two green roof areas, one over the parking garage and this one at the corner of the transparent conservatory building in center of the photo. Both predate the city green building ordinances, but have served as demonstration gardens for planners and builders. Seen on Wednesday, Sept. 29, 2021. (Olivia Sun, The Colorado Sun)

And a representative for a key builders’ trade group says the green ordinance, when piled on top of COVID-19 adaptation costs and recent inflation, has forced owners to put off altogether any renovations that might trigger regulation.

Even the ordinance’s minimum requirement for a renovated roof — a white, reflective membrane called a “cool roof” — is too expensive for most landlords right now, said Joe Havey, a past president of the Denver Metro Building Owners and Managers Association. Havey now runs an energy efficiency company, and sat on the task force that rewrote the green roof initiative into a broader, workable green buildings law. 

Instead of taking on major roof replacements that would lead to a green ordinance review, Havey said, most managers are making simple repairs and patch jobs. 

Regular maintenance on a big building’s roof is between $2,000 and $5,000 a year, Havey said, while a full replacement these days is in the hundreds of thousands of dollars. Meanwhile, changing pandemic habits leave building owners wondering where their tenants will come from and how much space they’ll want.

Between patching and replacing, Havey said, “the orders of magnitude difference are astronomical. And so, owners struggle with coming up with that two hundred grand to replace their roof.” 

The rewritten green roof ordinance broadened the categories that qualify as green renovation or green new construction. A cool roof is a minimum for many buildings. An additional green energy step is required, and those now range from adding solar panels, to rooftop or plaza green space, to detailed energy efficiency upgrades, to payments into a green building fund in lieu of compliance. 

“There’s various ways to meet the energy efficiency requirements, and they all cost money and time and effort and add on to the cost of placing that cool roof,” Havey said. “That’s the impediment.”

Bousselot and Rink, among others, believe the pace of new and renovated buildings getting permits under the ordinance will keep picking up. Planning a large building from ground up can take years, meaning some that got permits after the ordinance would only now be breaking ground, Rink points out. 

Besides, Bousselot said, increased efficiency at dozens of large buildings across the city is likely more than building owners would have done on their own, without new rules. 

“It takes policies like this to garner societal benefits from private development, and that’s the whole purpose,” Bousselot said. “Because most of the benefits of green roofs are realized at a societal level, when there’s a critical mass of green roofs in an area. You don’t get that voluntarily when it costs money — serious money.”

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...