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Green Roof

Green Roof Learning Center

Calhoun’s Green Roof Learning Center was the first eco-friendly green roof in NYC dedicated to educational study. 

The Calhoun School celebrated the opening of its new Green Roof Learning Center in May 2005. The space was designed by FXFowle Architects, PC as part of a four-story addition to the school's main building at 81st Street. The roof's semi-intensive design means it can be used as a functional outdoor space. 

Calhoun’s Green Roof offers multiple environmental benefits: it reduces storm water runoff; provides insulation to reduce heating and cooling needs; helps filter the air by absorbing carbon dioxide and giving off oxygen; and provides a food source for wildlife.

How Calhoun Uses Its Green Roof

Calhoun’s renowned food program often uses produce from our Green Roof herb garden. The Green Roof has been used as part of classroom curriculum on topics such as environmental and plant biology studies.

The Green Roof has also been used for community events, a source of inspiration for poetry classes, and a favorite escape from urban life!

How the Green Roof Came to Be

The idea for adding a Green Roof was initially suggested by a Trustee. The recommendation came at an opportune time, just as Calhoun was in the drawing-board stages for the four-story addition to the school's main building. 

Green Roof Design & System Details

  • System designed around the 50 pounds per square foot (psf) load requirement, a 10-inch deep green roof, with 5 inches of lightweight granular drainage media and 5 inches of light-weight.
  • The drainage media is 100% mineral and the growth media is greater than 92% organic. This is to provide a durable and structurally stable substrate for the turf.
  • Green Roof System: Roofscapes Inc.
  • Roof Membrane type: Fluid applied membrane
  • Insulation: rigid insulation and isocyanurate board
  • Growing medium depth (inches): 10 Inches for grass
  • Original Plant selection: Assorted Grasses, Sedum Album, Sedum Spurium alba Whiteform, Sedum Spurium Fuldagluu, Sedum Cauticolar, Lidakense, Sedum Sexangulare, Allium Schoenprasm, Petrorhagia Saxifraga. (New plants have been added and substituted)
  • Planting method: Grown in place
  • Drains : 4 roof drains in grass area
  • Irrigation System: Drip Irrigation
  • Accessories: Inset planting beds

Green roof type

  • Semi-intensive (grass with planting beds)
  • Total size of green roof (including paver area, sedum area and grass area): +/- 2,500 sf
  • The 'Turf System' –"Grass" roof area= 1200 Sq. Ft. The '6" System'-Sedum roof area 200 Sq. Ft. Rubber pavers surround the grass. Planter Boxes
  • Roof Accessibility: Accessible, ADA: (2) ramped walkways have been positioned running North/South along each side of the Turf System.


Original Project Team

  • Architect: FX Fowle Architects (formerly Fox & Fowle Architects)
  • Structural Engineer: Anastos Engineering
  • Construction Mgr.: Sciame
  • Green Roof Consultant: Roofmeadow (aka Roofscapes Inc.)
  • Green Roof System: Mfr Carlisle
  • Roof Membrane: MfrBig Carlisle
  • Growing Medium Mfr: Big River Industries
  • Growing Medium Distributor: Town and Gardens
  • Accessory Supplier Stabilized Grass Roof: The Motz Group

Green Roof FAQs

Green Roof

Green Roof engineering

Awards & Recognition

Design Award

Calhoun and FX Fowle Architects, PC, were named recipients of the 2007 Merit Award for innovative learning environments by DesignShare, an industry resource in the area of school construction. DesignShare jurors called the four-floor addition a "courageous design," with special mention of the Green Roof as "an innovation in the architecture for learning."

EE Ford Grant

Calhoun was among the small number of schools nationally that forged ahead in building a Green Roof, and was the first educational institution in New York City to build an eco-friendly Green Roof that is also functional for educational use. In recognition of Calhoun's leadership role in this area, the project received a $50,000 matching grant from the E.E. Ford Foundation, which supports innovative educational programs pioneered by independent secondary schools.

Top Green School

Shortly after the opening of the Green Roof, Calhoun was honored as one of the top Green Schools in the country by The Green Guide (July/August 2005). It has also been featured on