Denver has some of the nation’s most intense urban heat islands, that is when the metropolitan area is significantly warmer than surrounding rural areas. Typically, an urban heat island is most noticeable in the summer, when the sun heats up the concrete on roofs and streets, making the city about five degrees higher than nearby rural communities. Environmentalists have found that green roofs can combat this heat effect.

On January 1, 2018, Denver’s Green Roof Initiative went into effect. The ordinance requires buildings measuring over 25,000 square feet to dedicate a percentage of the building’s roof to green space. The statute was voted on by residents, as an update to the building code. It mirrors regulations written for Toronto and San Francisco, but backers have called Denver’s code one of the “most stringent in the U.S.” What do you need to know about this ordinance?

What Are Green Roofs?

The National Park Service defines a green roof as “a layer of vegetation planted over a waterproofing system that is installed on top of a flat or slightly–sloped roof.” The green roof essentially replaces some of the plants that were removed when the building was constructed.

Green roofs have many benefits:

  • Improve stormwater management to reduce runoff
  • Conserve energy
  • Reduce urban heat island
  • Reduce air and noise pollution
  • Provide habitat for wildlife
  • Beautifies city, leading to a better quality of life

Green roofs work in any climate. San Francisco and Toronto have green roof requirements. Germany is a leader in green roofs in Europe. Washington D.C. has the most green roofs in American, probably due to its rebates for installing a green roof. Chicago offers zoning initiatives for businesses that install a green roof.

How Does Denver’s Green Roof Initiative Affect Your Building?

The Green Roof Ordinance only affects certain buildings, including commercial buildings 25,000 square feet or larger and residential buildings over 4 stories and more than 25,000 square feet in Denver are affected, but there are exemptions. One key exemption is for existing buildings that would require significant structural alterations to manage the weight of a green roof.

New buildings that are being constructed will have to implement a green roof system based on the size of the building. For example, a building 25,000-49,999 square feet are required to cover 20 percent of the available roof space with a green roof and solar panels. For buildings, 100,000-149,999 square feet, the percentage of required green roof and solar panel coverage increases to 40 percent.

Gross Floor Area
(Size of Building)
Coverage of Available Roof Space
(Size of Green Roof)
25,000 – 49,999 f2 20%
50,000 – 99,999 f2 30%
100,000 – 149,999 f2 40%
150,000 – 199,999 f2 50%
200,000 f2 or greater 60%

Developers and building owners are required to pay for the operating costs of the green roof. Currently, in Denver, there are no other incentives, but it might be wise to check out funding initiatives offered by the EPA, HUD, and others to see if your organization qualifies for grants or government loans.

Current buildings that are 25,000 square feet or greater do not have to comply with the new requirements until they do a standard roof replacement. Commercial roofs last about 15 years. Green roofs should last 2X-4X longer, which is another benefit of installing a green roof. It’s expected that these systems will lower the long-term operating costs of the building. Proponents of the initiative hope that savings will be passed along to the tenants.

Applying for a Green Roof Building Permit

Currently, the application for roofing permits is not available for online submission. The Green Roof Declaration Form is online, but it must be completed and emailed or sent to the Denver Planning Board for staff to review. You can use this form if you are asking for an exemption or requesting a roofing permit. The form is five pages and includes a checklist of documentation needed to back up your project or exemption. It should help property managers and building owners follow the new regulations. The list of documents is substantial. Plans and reports from engineers, landscape architects, maintenance, and more are required as part of the application. This is not something that you can simply pull together in a short time frame.

Property managers and owners of buildings that fall under this new ordinance should be prepared to make plans now for a green roof or to get the documentation that exempts your building from having to install one. It should be a be part of the long-range planning for your property.