When you think of commercial buildings in midtown Manhattan, green space isn’t the first thing that comes to mind. However, that might be changing. When it came time to replace the roof on the United States Postal Service (USPS) Morgan Mail Processing and Distribution Center on Ninth Avenue in New York, a vegetative roof was at the top of the wish list.

When you think of commercial buildings in midtown Manhattan, green space isn’t the first thing that comes to mind. However, that might be changing. When it came time to replace the roof on the United States Postal Service (USPS) Morgan Mail Processing and Distribution Center on Ninth Avenue in New York, a vegetative roof was at the top of the wish list.

Built in 1933, the building is designated a historical landmark. It’s also as big as a city block and serves as a major mail sorting facility that operates 24 hours a day. When the existing built-up asphalt roof began to fail, the USPS looked at options to reduce energy usage as part of its goal to reduce energy use by 30 percent by 2015. The objective was to incorporate a garden roof without busting the budget and recycle or reuse as much of the material as possible - all without disrupting normal operations at the facility.

Working closely with the USPS, the construction and design teams from Turner Construction, URS Corp., EKLA landscape architects, and Tecta America’s JP Patti Roofing and Magco units installed nearly 2.5 acres of green roof as part of the 109,000-square-foot overall roofing project. The project was completed on time, under budget, and without interrupting the facility’s operation. The result is a complete transformation of the site and the largest green roof in New York City.

The new roof system consists of Sika Sarnafil 80-mil PVC loose laid membrane installed over 1/4-inch DensDeck board and 3 inches of extruded polystyrene insulation. Concrete pavers cover another 12,700 square feet. Some 63,000 square feet was covered with a protection sheet, drainage mat, separation fabric, water retention mat and growth media. Most of the garden roof area has 4 inches of growth media, with some 8-inch-deep areas. A variety of plants were installed, and nine trees were placed in a planter along the center of the roof.

I recently spoke Angie Durhman of Tecta America to get her perspective on the project for an article that will be included with our September issue. Durhman, Green Roof Manager for Tecta America, has a background in horticulture and she works with all of Tecta’s operating units on green roof projects.

“As Green Roof Manager, I take care of the overburden for these living roofs,” she said. “I work on the design, project estimating, actual project management, and maintenance.” The original scope called for 12 inches to 18 inches of soil, but it was reduced to the 4-inch and 8 inch soil profiles to fit the project’s budget.

Plants were chosen that would thrive in the local environment, including sedum, drought-tolerant grasses and perennial flowers, including coreopsis. Serviceberry trees were in a planter in the center of the roof. Plants were irrigated during the establishment period, but there is no permanent irrigation system. The plugs grew in quickly. “Within about eight months we had 80 percent coverage,” she said.

Coordinating the delivery of the plants was crucial, noted Durhman. “As soon as they were taken off the truck they were craned up within the hour and planted that same day.”

Tecta America’s services include a two-year maintenance agreement. “We are maintaining the roof to eliminate any weed presence, in case random grasses or weeds are dropped on or blown on the roof,” Durhman said. “We make sure plant health is good.”

The company prides itself on handling all phases of green roof projects, and Durhman, noted the single source for warranty work is an added selling point.

The roof is estimated to last 50 years, minimize storm water runoff and save an estimated $30,000 a year in heating and cooling costs. The improved aesthetics are the icing on the cake.  

“I think if you took a snapshot of Manhattan, there are a lot of unusable roofs for green applications - too small, too much equipment, etc.,” Durhman said. “I’d like to recognize the post office for realizing that the roof posed a great opportunity for green space. Open roofs - there aren’t a lot of them in Manhattan, but we want owners to consider them for green projects as well.”