Denver could soon be budding trees, vegetable gardens and/or solar panels atop its roofs under a November ballot question, but the initiative has proven unpopular at least among city officials and developers.

Alongside school board races, GO Bond proposals and other initiatives, Denverites will be asked on the ballot to consider whether the city should require newly-built, larger buildings to have “green roofs.” Initiative 300, or the “green roof initiative,” would require new buildings larger than 25,000 square feet to dedicate a portion, about 20 percent, of their rooftops to vegetation or solar panels.

The environmentally-friendly idea behind green roofs is they would help reduce Denver’s urban heat island effect. Rooftops absorb warmth from the sun, raising the city’s temperature by nearly five degrees, the citizens group behind the initiative said. Denver ranks third in the nation for urban heat island, according to USA Today, behind Las Vegas and Albuquerque. The green roofs would help cool Denver, reducing energy consumption in the city.

It’s not the idea of green roofs but the ordinance itself that has garnered mounting opposition.

In a statement Tuesday with the Citizens for a Responsible Denver (the organized opposition to the initiative), City Council members Kendra Black, Kevin Flynn, Stacie Gilmore and Mary Beth Susman said while they support environmentally-friendly policies, it’s the lack of flexibility and unintended consequences associated with the ordinance they can’t get behind.

“Denver is becoming less and less affordable for our hardworking families,” Black said. “Let’s not make it any more expensive with the ill-conceived mandate for green roofs.”

Flynn noted he has vacant commercial buildings in his district, and he fears the initiative would serve as an obstacle to their re-use.

“This measure alone would likely put future re-use out of reach. Green Roofs and especially mandates, should require greater community input than a two-month campaign,” Flynn said.

And Mayor Michael Hancock has also come out against the initiative, arguing “Initiative 300 is not the right approach for Denver. It goes too far too fast and provides no flexibility or opportunity for ‘carrots’ instead of ‘sticks.'”

Developers have also joined the opposition, as Westword notes, with every donor to Citizens for a Responsible Denver, “either directly involved with or related to developing, including the Associated General Contractors of Colorado, Denver Commercial Association of Realtors and the Colorado Association of Mechanical and Plumbing Contractors.”

Citizens for a Responsible Denver have raised $41,500 in campaign donations – more than six times that of The Denver Green Roof Initiative, according to Westword.