Backers of Denver’s Green Roof Initiative expressed cautious optimism late Tuesday as their far-reaching measure, which would require rooftop gardens on most new buildings (and some existing ones) with at least 25,000 square feet of floor area, was leaning toward passage.

At 2:00 a.m. Wednesday, with more than 96,000 votes counted, 52.17 percent of voters supported the measure and 47.83 opposed it, according to Denver Elections Division results.

The 4.34-percentage-point margin has grown with every release of new results, with the vote difference increasing from about 2,000 on the late evening to more than 4,100 overnight.

The Elections Division suspended counting at 2 a.m. Wednesday and expected to resume at 10 a.m. A spokesman, who cited heavy Election Day turnout, said the next results update would occur at 3 p.m.

But things were looking up for the proposal’s backers, with late voters supporting it more strongly than early voters. They were tentatively declaring victory.

2017 Results Green Roof Initiative

“This was David and Goliath,” Sunshine Benoig said at a Denver watch party for backers of the initiative, “and David won once again.”

Brandon Rietheimer, the measure’s founder and campaign manager, said he was feeling “pretty good” after the first results came in. By the third tally, he was nearly ready to declare victory.

“I think we’re in the clear. It’s hard to say, but it’s looking really good,” he said. “I think it shows we in Denver want more leadership on sustainability. We’ve had all these goals in place but no plans of action to reach them — and this is a clear path to a more green future.”

Backers of the Denver initiative, who launched a grassroots campaign to get it on the ballot, say their proposal would alleviate the city’s large urban “heat island” effect, caused by heat-radiating pavement and rooftops.

However, opponents have argued that mandating rooftop gardens and solar energy arrays — which could be used to offset some of the green roof requirement — would force builders and property owners to deal with burdensome, extra costs.

“We’re of course disappointed,” said Kathie Barstnar, co-chair of Citizens for a Responsible Denver, the committee that’s leading opposition to the initiative. “We would have liked to have seen a different result, but we will take some time now to look at what our options are. We still have great concerns for the impact this will have on the city and county of Denver (and) on the ability to attract development to the city.”

Barstnar said one of her worries was that the measure could hamper the many city projects that were slated to be paid for by the nearly $937 million bond package approved by Denver voters on Tuesday night.

If the Green Roof Initiative ultimately passes, it would take effect Jan. 1, which likely means there will be a rush to submit building permit and site plan applications before then in order for projects to be exempt. Beginning in six months, the Denver City Council would have the option of repealing the new voter-initiated ordinance, or making changes, with a two-thirds majority.

Mayor Michael Hancock last month was among those who came out against the Green Roof Initiative, saying it “goes too far too fast.” The Denver Metro Chamber of Commerce and the Downtown Denver Partnership are among several business groups that opposed the measure as well.

Those against the proposal drew a roughly 12-to-1 financial advantage over its proponents, with campaign finance reports filed last week showing the opposition committee raising nearly $250,000 in direct donations since members of the Colorado Real Estate Alliance formed it in mid-September.

The local environmental activists behind the Denver Green Roof Initiative hauled in just $21,564.

Another point in the initiative’s David vs. Goliath dynamic: Backers watched Tuesday’s results at a smaller Denver Mexican restaurant and tequila bar, while opponents gathered at John Elway’s steakhouse in Cherry Creek.

At the Mexican restaurant, the measure’s backers were feeling good about their chances after the first results came in. And as the night wore on, their confidence grew.

Andy Creath said if the Green Roof Initiative passes, it would be “vindication for people’s word over corporate money.” Miranda Glasbergen, at the watch party, said she was feeling very proud of what supporters of the measure have accomplished even if they don’t win.

“We pushed the envelope with this initiative,” Glasbergen said.

If approved, the Denver Green Roof initiative would give the city some of the most stringent and far-reaching green-roof requirements in the nation.

Size-based coverage requirements would apply to most new buildings with at least 25,000 square feet of gross floor area beneath the roof, as well as to existing buildings above that threshold when their roofs are replaced or when building additions push the floor area above the threshold.

The green-roof coverage requirements would start at 20 percent of the roof area and ratchet up to 60 percent, depending on a building’s total square footage and type. The initiative exempts residential buildings of four stories or less.

There were fears among detractors that higher building costs could be passed on in the form of even higher rents.

However, the Toronto-based Green Roofs for Healthy Cities and the Green Infrastructure Foundation released a study — in support of the Denver proposal — estimating that if the proposed ordinance were approved, it would result in the building of 57.5 million square feet of green roofs by 2033. Over the first 40 years, that study says, green roofs could generate $1.85 billion in energy savings and other benefits.

The city with a policy closest to Denver’s proposal is San Francisco, which was less intensive, came from a city council-passed ordinance and resulted from years of collaboration with stakeholders.

It’s not entirely clear how the low turnout for this year’s Denver election — it was just shy of 21 percent in Denver through early Monday night — impacted the results.