Aug 26, 2010

City Reso: Green Roofs allow Floor Area Density Bonuses

City Resolution 10-230: “PROPOSING ORDINANCES RELATING TO AN AMENDMENT TO CHAPTER 21,  REVISED OF HONOLULU 1990 (THE LAND USE ORDINANCE), GREEN ROOFS,” was introduced on August 12, 2010 and was referred to the Committee on Zoning.

The resolution directs the Dept of Planning & Permitting to prepare a report and propose an amendment to the Land Use Ordinance for Green Roofs. This is just a proposal at this point and far from becoming law.

The proposed changes would allow density bonuses for installing a Green Roof in Residential, Apartment, Business and the Waikiki Special District. The greater % of area devoted to Green Roof, the greater the bonus.

For example, a residence would be allowed to exceed to 50% lot coverage by providing a Green Roof.
  • Green Roof 10% of Bldg Footprint = 1 sq ft additional building area per 1 sq ft of Green Roof
  • Green Roof 30-60% of Bldg Footprint = 2 sq ft additional building area per 1 sq ft of Green Roof
  •  Green Roof 60%+ of Bldg Footprint = 3 sq ft additional building area per 1 sq ft of Green Roof
For Residential properties, Building Area is not the same as Floor Area.
  • Building Area is the Lot Coverage or footprint of all structures. (ie. 1st Floor only)
  • Floor Area is the total area contained within the structure. (ie 1st and 2nd Floor combined)
  • For apt, business and Waikiki SDD zones, Green Roofs would increase Floor Area.
 The Land Use Ordinance would also be revised to include a new definition: “Green roof,” also known as “eco-roof,” “vegetated roof cover,” or “living roof,” means a roof covering comprised of multiple layers of waterproofing, drainage, growing media and plant material forming a permanent vegetative layer over the roof deck, living plants, of which not less than 50 percent are endemic to the Hawaiian Islands, installed on top of conventional roofs, which, if properly designed, are stable, living ecosystems that emulate natural processes.”