On Nov. 8, 2017, the voters of Denver passed the Denver Green Roof Initiative. As of Jan. 1, the construction of any building with a gross floor area of 25,000 square feet or greater must include covering a portion of its roof with vegetation, solar panel installations or a combination of both. The Initiative is codified as Article XIII §§ 10-300 et seq. to Title I, Chapter 10 of the Denver, Colorado Code of Ordinances.
Supporters of the initiative assert the new requirements will mitigate Denver’s growing ozone/particulate pollution output and alleviate Denver’s “urban heat island” effect, a condition in which an urban area becomes significantly warmer than its surroundings due to development density and a heavy concentration of heat-retaining pavement and concrete. Supporters contend the “improvements” will reduce long-term operating costs and overall energy consumption through the use of solar power and offsets to costs and energy currently devoted to water drainage. Additionally, supporters claim the rooftop vegetation will extend a roof’s longevity by providing added protection to its waterproofing membrane.
The initiative passed despite heavy opposition from powerful local actors including Mayor Michael Hancock, the Denver Metro Chamber of Commerce, the Downtown Denver Partnership, the Visitors Bureau and development groups. These groups insist the initiative will drive up development costs and contribute further to the overvaluation of Denver’s housing market. Mayor Hancock expressed concerns that the initiative’s mandate-only approach eliminates opportunity to implement a phased infrastructural plan aimed at addressing environmental concerns that could ultimately yield more effective long-term results while avoiding the repercussions the initiative currently poses to developers and property managers. The chairwoman of Citizens for a Responsible Denver, a coalition of Colorado businesses opposed to the initiative, said she is troubled by the fact that institutions like Denver Health might now be forced to spend less on, or postpone indefinitely, future projects such as expansion or the construction of a new facility to pay the costs required to satisfy the initiative’s requirements.
It is estimated the initiative’s measures will cost a developer an average of an additional $15 per sf. However, it is unclear whether that number is entirely reliable considering the initiative requires existing buildings meet its mandates in two circumstances:
- When existing buildings that fall within the square footage parameters of the initiative inevitably require a roof replacement, and
- When existing buildings construct additions causing them to fall within the square footage parameters.
Consequently, it is not unreasonable to think that “retrofitting” such roofs could come with unanticipated costs and issues.
The initiative provides for a corresponding increase in the percentage of “green roof space” in relation to the gross square footage of floor area within a building. For example, a building with a gross floor area of 25,000 to 49,999 sf must cover 20 percent of its available roof space in vegetation or solar installations. A building with a gross floor area of 200,000 sf or more must cover 60 percent of its roof with the same.
A combination of solar installations and vegetation may be used to fulfill the green roof space requirements only if “the combination is no less than 30 [percent] green roof and retains or collects for re-use at least the first 0.25 inches from each rainfall or 50 percent of annual rainfall volume falling on the roof through systems that incorporate roof surfaces.”
Developers must have a permit issued by the Community Planning and Development Department to construct or cause to be constructed a green roof. Furthermore, where a “complete site application” indicates a development will include two or more buildings, and such buildings are to be constructed in phases, the green roof requirements must be met in the first phase of development to obtain a permit for the whole project. Any green roof area in excess of the 25,000-sf minimum may be applied to subsequent phases of the development.
Applications for a green roof construction permit must be made to the Community Planning and Development Department through a Green Roof Declaration Form. The form requires disclosure of information including, but not limited to, structural design, intended use of the roof, whether it will have private or public access, and information about fire safety. There is no additional application fee when the required green roof application is sought in conjunction with a general building construction permit. When an application is made for an alteration or renovation to construct a green roof, the fee is the same as it is for the building permit classification.
All green roofs must be constructed and maintained according to the Denver Green Roof Construction Standard – the mandatory provisions of which prescribe rules relating to green roof assembly, gravity loads, slope stability, parapet height, overflow scupper locations, wind uplift, fire safety, occupancy safety, waterproofing, water retention and drainage, vegetation performance, plant selection, irrigation and adherence to an approved maintenance plan.
Importantly, the initiative includes certain exemptions. The green roof requirements do not apply to:
- Buildings or building additions for which completed building permit applications or completed site plan applications were submitted before Jan. 1, 2018;
- Residential buildings or residential building additions for buildings with heights less than or equal to the greater of either 50 feet or four stories;
- Commercial greenhouses located at ground level;
- Temporary structures; and
- Air-supported structures.
When a building’s green roof space is less than what is required according to its gross floor area because of a variance or exemption, the developer or property manager must make a cash payment in lieu of meeting the mandates of the initiative. The payment amount is $25 per sf equaling the unsatisfied percentage of required green roof space.
Violations of the initiative are enforced by officials of the Development Services Division of the Community Planning and Development Agency. A person convicted of a violation may be assessed a fine up to $999, imprisoned for up to one year, or both. Each day a violation or offense continues constitutes a separate violation. If an enforcement officer provides a cease-and-desist notice, proceedings may be initiated against the violator no sooner than 10 days after the date of notice for all parties except the owner.