By Chris Erickson
This past summer, around the same time the NYC city council passed the Climate Mobilization Act requiring green roofs on new buildings, one of the oldest green roofs in the city celebrated its tenth birthday. At ten years old the green roof on the Linda Tool manufacturing company in Red Hook is thriving. It has dramatically reduced the building’s environmental footprint, created valuable habitat, and brought natural beauty to the neighborhood. Touring the roof, as the Highview Creations team did on a cloudy summer Friday, is an exciting glimpse into where our city is headed.
Installed by Highview Creations co-founders Eric and Mark Dalski along with Project Manager Peter Spartos in 2009, the Linda Tool roof covers 12,000 square feet and is built with a lightweight Gaia Technologies soil medium that varies in depth from four to eleven inches. The minimum soil depth required to build a green roof is typically just two inches, and having the extra depth allows for a much wider community of plants to grow. However, the Linda Tool roof does not have permanent irrigation and plants growing there must still be highly resistant to drought conditions.
The primary motivation for building the Linda Tool roof was to cut down on stormwater runoff and in this it has succeeded wildly. Faculty and students from Columbia University conducted assessments before and after installation and measured an 88% reduction in runoff volume. The soil, and the plant roots holding it together, act as a giant sponge that absorbs and utilizes rainwater instead of allowing it to flow off the roof.
Because New York City’s outdated sewage system flushes raw sewage into our waterways when rainwater overwhelms the system (which is an increasingly frequent occurrence), this reduction in runoff translates directly into less raw sewage entering the nearby waterways. The Gowanus Canal Conservancy has called for green roofs to be a central part of their vision for the Gowanus Canal’s recovery, and the Linda Tool roof has been demonstrating the wisdom of this approach for ten years.
Of course, as an extra benefit the Linda Tool roof also helps mitigate the urban heat island, as all green roofs do. The day we visited was a typically hot, muggy summer afternoon and the roof was noticeably cooler than the surrounding streets, for which I was grateful. On a similar note, the soil and vegetative layer has led to dramatically reduced air conditioning bills for the building below.
The plant community on the roof that is responsible for these environmental benefits has evolved over the past ten years. This evolution is common on green roofs where specific local conditions can favor unexpected plant species. The area was originally planted as a meadow with plants that were chosen for being pollinator-friendly while requiring minimal maintenance. Three of the most visually prominent that remain are joe-pye weed (Eutrochium purpureum), beebalm (Mondarda fitsulosa), and common milkweed (Asclepias syriaca). These original plants have been joined by tough colonizers from the rest of Brooklyn, both native and non-native in origin, and the result is a balanced plant community. The only maintenance besides supplemental watering is occasional hand pulling of particularly aggressive invaders such as phragmites.
The variation in soil depth on the Linda Tool roof has led to the formation of distinct vegetative zones as larger plants requiring bulkier root systems pack into the deeper middle section and tougher, more drought resistant species occupy most of the roof edges. With small paths worn down by foot traffic meandering around the roof the visual diversity creates a pleasing sensation of an expansive natural space. Varying soil depth is a great strategy for introducing variety and dynamism to the flat, geometric shapes of rooftops and it was exciting to see how plants had responded to it on their own.
The hallmark of an ecologically productive plant community is a healthy insect population, and every time the sun peeped out the air was thick with bees, butterflies, and other pollinators. Even more exciting, a good number of dragonflies and damselflies were flitting about. Members of the order odonata, these insects are the top of the insect food chain and their survival requires abundant populations of smaller insects, an easy indicator that we were standing on a robust ecological community.
The Linda Tool roof is barely a mile from lower Manhattan and as we walked around I enjoyed finding vantage points where the tall joe-pye weeds and monardas blotted out the nearby buildings so that this one roof, surrounded by city on all sides, felt like a world wholly apart. Knowing the recent Climate Mobilization Act is set to rapidly expand green roof coverage across the city made our visit to Linda Tool’s pioneering green roof all the more exciting. These new green roofs can mean dramatically reduced runoff, a cooler city, expanded wildlife habitat, and just plain better views.
As a reminder, if you are curious about what the Climate Change Mobilization Act means for your roof check out our page on Green Roof Legislation in NYC.