Initiated Ordinance 300 – better known as the Denver Green Roof Initiative – was passed in November 2017 with a total of 137,917 votes. The ordinance requires that all buildings within the City and County of Denver in excess of 25,000 square feet, must now dedicate a percentage of the building’s roofing area to a combination of vegetative space and solar. Unlike larger cities with similar requirements, such as San Francisco or Toronto, Denver’s Initiative applies both to new buildings as well as existing buildings at the time of roof replacement or major repair. While certain limited exemptions do exist,1 all exempted buildings are required to provide a cash-in-lieu payment to the Denver Office of Sustainability equal to the cost of constructing the green roof.

The specific requirements for roof surface dedication depend upon the square footage of the buildings:

The Initiative also sets forth stringent Green Roof Construction Standards, including the following, among other provisions:

  • The assembly of a roof repellant system, a drainage system, a filtering layer, a growing medium, and of course plants.
  • Installation on a waterproof membrane of an applicable roof.
  • All roofs with slopes in excess of 10° (17%) must incorporate anti-shear measures.
  • Adequate irrigation to initiate and sustain the vegetation during the service life of the green roof.
  • Water retention mats or equivalent materials.
  • Development of a maintenance plan for the green roof.
  • Calculation of green roof gravity loads provided by ASTM International.
  • Submission of a report confirming that the engineered system provides plant survivability.
  • Submission of a report, stamped by an engineer, providing wind uplift pressures being designed for (including a description of how the pressures were determined), and describing how the design addresses these pressures.

The unprecedented requirements set forth in Denver’s Green Roof Initiative not only underscores the importance of obtaining law and ordinance coverage, but further demonstrates the difficulties policyholders face in determining how much law and ordinance coverage to obtain, as pointed out in prior Property Insurance Blog posts by Chip Merlin and guest contributor Brent Winans. While the full impact of the initiative remains to be seen, policyholders within the purview of Denver’s Green Roof Initiative should seriously consider a customized appraisal to best determine the estimated cost of satisfying such strict requirements prior to even attempting to make a decision regarding the necessary amount of law and ordinance coverage to include on their policy.

1 Section 10-301(A) does not apply to a residential building or building addition to a residential building with a height less than or equal to the greater of four stories or 50 feet.