South Bronx Green Roof tour

A green roof is a roof of a building that is partially or completely covered with plants and soil.

On Friday, I was lucky enough to get pulled off of the wait-list for a spot on the Bronx Overall Economic Development Corporation’s (BOEDC) tour of six South Bronx green roofs that have been developed with the assistance of BOEDC loans.

Entering the tour, I had three main questions: 1. COSTS: How expensive is a green roof to build, install and maintain? 2. BENEFITS: Have concrete, quantitative benefits been measured? 3. STRUCTURAL REQUIREMENTS: How complicated is installation? Can any building house a green rooftop?

Here’s what I learned:

Cost:The cost of installing a green roof typically ranges from $15 – 28 / sq. foot. The Bronx County Courthouse green roof, for example, cost $23 / sq. foot (including design, labor, plants, installation, and the first two years of maintenance). But things are getting cheaper -- In Germany where the market is well established (10% of rooftops in Germany are green) and government incentives encourage greenroof development, greenroofs are about 1/10 the cost. Go Germany! Here in New York a green roof tax credit passed in New York State legislature just last week – buildings with green roofs will now get a tax rebate of $4.50 / sq. foot!

Benefits: A whole slew of benefits have been documented in connection with the BOEDC greenroofs, and more data is being collected every day thanks to careful collection and analysis made possible by EPA grants. In the Bronx Courthouse, the green rooftop has been documented to be ~70 degrees cooler than the non-green roof area, and the floor directly below the roof has been saving 30% on AC and heating costs. Research has also shown that green roofs keep 40%-70% of rainwater from running off of buildings and flooding nearby drains, saving the city money on stormwater treatment and preventing pollution from sewer overflows. Other benefits include carbon storage, the dampening of noise pollution, and the provision of a quiet, green retreat.

Structural requirements: BOEDC literature reports that green roofs add about 28 lbs / sq. ft of weight to a roof. I had thought that buildings need serious retrofitting to be able to handle this load, but this is actually not the case. Most buildings built before 1967 can bear the weight, and many other newer buildings can as well. (Also, greenroofs have been proven to actually extend the life of existing roofs by protecting them from the elements.)

Here are some photos from the tour:

Bronx Municipal Courthouse:



St. Simons School: Unlike the other roofs on the tour, St. Simons’ was planted not with sedum (ground hugging, hearty, succulent plants that grow well in bright and hot places), but with plants native to New York City. The native plants need watering, whereas sedum mostly don’t require irrigation after they’re established. Consequently, this green roof was a bit browner than the others.


Sustainable South Bronx: Since SSBX rents their space, they brought up a series of movable modules instead of installing permanent infrastructure. This makes the design flexible, but it was more expensive to implement since they couldn’t buy things in bulk.


Grandparents Family Apartments / Abraham House:
Grandparents Apartments is a building for grandparents who are raising their grandchildren. Abraham House is housing for families impacted by incarceration. Both of these greenroofs were urban oases available to the buildings’ residents -- The best part of both rooftops were the benches. In addition to their environmental benefit, these roofs were also designed to be for people to sit and passively enjoy the roof and the view. Both roofs also had some really beautiful, succulent sedum.



Fordham Bedford Houses:
Bees! Everywhere! Someone should get up there with a hive and make some South Bronx honey. This roof, established by the ‘carpet system’ where the plants and soil were brought up in a roll and unfurled, was yellow and beautiful.