Green Roofs and Eco-friendly Buildings Show a Trend in Public and Private Sectors

A national study on large buildings indicates that cities and developers are serious about going green

In January, a Denver ordinance went into effect that requires green roofs to be put on all new buildings as well as on existing buildings once their roofs are replaced. It was strongly supported and opposed, but people from both sides have worked together in the past few months to make it more flexible and realistic. It is only a part of a larger trend in environmentally minded construction around the nation.


Despite garnering voter approval, the language of Denver’s ordinance needed work, as evident by how Katrina Managan of the Denver Department of Public Health and Environment was given the task of leading a process for changing the initiative. That process lasted until June 15 and the City Council will vote on the issue in October at the earliest.

Managan said there were problems translating the ordinance from Toronto’s building codes, which inspired it, to Denver’s municipal codes. Also, since about 90 percent of existing buildings cannot support the weight of a green roof, a vast majority of buildings would get exempted. The initiative was very narrow in what would count for compliance, a rooftop garden or solar panels and that’s it. “What we really want to honor is the benefits the voters were going to get from that ordinance,” said Managan. Her goal was to be sure the voters at least got what they voted for in spirit.

The original ordinance required that all new buildings’ roofs have plants,  solar panels or both. And any existing building over 25,000 square feet would need to meet those requirements once it needed a roof replacement. There is an exception for existing buildings that are residential and five or fewer stories tall.

The result is that building owners could instead install a green space anywhere on their property, avoiding the structural problems of putting a green roof on an existing building. The same principle can be put to solar panels, which, for example, can be put on shade structures in a parking lot rather than the building’s roof. While more buildings can carry the weight of solar panels than can support vegetation, flexibility can encourage greater adoption, Managan said. The task force also proposed regulations that say buildings can subvert the requirements by increasing their energy efficiency to be equivalent to the energy potentially produced by solar panels so that there is no need to install anything. If a building owner does not want to do anything in this vein, they can pay a fee, and the city will create a green space elsewhere.

Managan said there are four main benefits to adopting green rooftops. First, it would reduce the “urban heat island” made by all of the black surfaces absorbing heat from the sun by reflecting sunlight. Denver has one of the worst heat islands in the country. Green roofs also would manage water runoff during storms, making it less extreme. Third, Managan says people don’t want to live in a concrete jungle and would appreciate a “green experience.” Finally, the solar panels would reduce a building’s greenhouse gas emissions.

Senior Managing Director of Trammell Crow Company’s Denver office, Bill Mosher, voiced his opposition toward the original ordinance. “Green Roofs aren’t the only answer, putting vegetation on a roof doesn’t necessarily solve any problems, we need more tree canopy in the urban landscape and putting it on roofs doesn’t do any good,” he said. He admitted that the process the ordinance has gone through this year opens up options for compliance to allow any particular site to do what works best for it. He thinks that the trend in environmentally conscious design and construction is recognizing that one size does not fit all.

Expanding the Idea of Green Construction

While Denver is new to regulating green rooftops, the city has already made attempts at improving the environmental aspects of construction and real estate. 

Green rooftops are only one avenue towards a more environmentally friendly cityscape. Standards for green buildings set by the U.S. Green Building Council and the Environmental Protection Agency have proven to be attractive to developers. Over the past 13 years, the number of buildings and the total square footage of buildings that are certified by one or both of those agencies has grown immensely in 30 cities. 

That information comes from an ongoing study by the real estate firm CBRE, that is a parent company to Trammel Crow. The firm works in conjunction with Netherlands-based Maastricht University to rank cities by how environmentally friendly their large buildings are. In the most recent report, Denver was ninth of 30 listed with 45.2 percent of building space certified to meet LEED or Energy Star standards. LEED, the USGBC standard, stands for Leadership in Energy Environmental Design. Energy Star is the EPA’s standard. 

A total of 209 buildings in Denver were counted as certified in the 2018 report. In all of the categories the CBRE report looked at, Denver still exceeded national averages. As a comparison, Chicago, which was ranked first, has 69.8 percent of building space certified.

David Pogue, senior vice president of Global Client Care at CBRE, said that nine of the top 10 cities in the report had an ordinance requiring buildings to measure and disclose energy usage. Denver is one of those cities, requiring any building over 25,000 square feet to give a report. “You can’t manage what you don’t measure,” said Managan. The Department of Public Health and Environment stated that other cities using energy reports saw energy savings improve by 2 to 3 percent.

Denver, unlike Chicago or California, does not have rules on the books that buildings must meet equivalents to LEED or Energy Star standards. Colorado’s standards are instead under the International Energy Conservation Code that covers things like energy efficiency for lighting and heating in residential and commercial buildings.

Pogue, said that often developers are convinced to match LEED standards due to tenant demands, investors wanting a building that is worth more or having to follow city requirements like in Chicago or California.

“The Denver market has the characteristics of the quality of the buildings, the type of ownership, the demands of the tenancy and the community and cultural kind of requirements,” said Pogue on why Denver has as many LEED or Energy Star certified buildings as it does.

Denver isn’t the only place in Colorado that is creating green building codes. Telluride adopted such a code that requires new construction for commercial and residential buildings to have better energy and water efficiency as well as offset the energy used in development of the buildings. Golden has a 10-year plan for 90 percent of new buildings and 50 percent of all remodels to meet green building standards, like LEED, for its municipal buildings. Superior has a Green Building Program for energy efficient building standards when it comes to development and redevelopment.

There are also economic reasons to take the extra step to meet LEED or Energy Star standards. Both Pogue and Mosher said how the materials available to meet requirements are easier and cheaper to get and use. 

CBRE is finding in its research that there is a plateau in number of buildings becoming LEED or Energy Star certified. Pogue said this is because almost every building that should be certified already has been. Another factor, as can be seen in California, is that buildings have to meet LEED standards to comply with a city’s codes. Because of that, companies don’t see a reason to pay for the processing of certifications when everyone knows that the building is at that level already.

The degree to which the real estate field has shifted to be environmentally conscious is considerable. Pogue said, “The commercial real estate business, I think, has been remade in the last decade about the way it cares, about the way it manages, about the way it measures, about the way it reports on things like recycling.”

However, developers are always looking for things that will set their buildings apart from the competition. While LEED certification used to be the way to do that, it’s no longer unique. Pogue and Mosher said that the next types of certifications CBRE will measure, and think developers will pursue, are about health and wellness standards for employees working in the buildings or a score of how technologically advanced a building is.

— Connor Craven

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