Green Roof Learning Center

The Green Roof acts as insulation for cooling and heating, thereby providing energy savings. It also cuts rain water surge run-off by half, so that it decreases stress on sewer systems. It contributes to cleaner air and acts as a habitat for insects. There is evidence that, while more expensive initially, green roofs extend the life of the rooftop.

The lunch program has been a major beneficiary of the vegetables and herbs grown on the Green Roof.

The Green Roof Learning Center has been used by teachers for environmental and plant biology studies as well as for units in geometry. The Green Roof has also been the site of an outdoor art installation and various community events, a source of inspiration for poetry classes, and a favorite escape from urban life!

Calhoun is the first educational institution in New York City to design an eco-friendly green roof that offers multiple environmental benefits while providing programmable space for outdoor science and environmental studies. Towards that end, the project received a $50,000 matching grant from the E.E. Ford Foundation, which supports innovative educational programs pioneered by independent secondary schools.

In its 2005 annual report, The Green Guide (a consumer magazine and online publication) applauded Calhoun as one of only 15 schools nationwide for efforts in the areas of environment and nutrition. Calhoun received two honorable mentions from the editors: as a "High Performance Building" for its new eco-friendly Green Roof, and for "Sustainable Food and Healthy Diet" thanks to Calhoun's pioneering Eat Right Now lunch program. The awards were announced at a press conference in September 2005.

In response to ongoing inquiries and in recognition of our responsibility as a role model in the greening of our community, Calhoun has and continues to offer tours of the Green Roof Learning Center to educators, students, architects and legislators.

Calhoun's Green Roof was completed in September 2005, following a major expansion that added four floors to our main 81st Street building. During the design stages of the expansion, a trustee brought the idea for a Green Roof to the attention of the Board. Based on a cost/benefit analysis - which took into account the long-term environmental benefits and energy savings as well as the opportunities for curricular enrichment — the Board overwhelmingly approved the plan and added expenditure. Plans for the Green Roof were designed by FXFowle Architects, with the help of the Earth Pledge Foundation.

Calhoun's Green Roof is a European-engineered, multi-layered, semi-hydroponic, rooftop agri-system. It is also an INTENSIVE green roof, as opposed to an extensive green roof (see Green Roof Facts for specs.)

The Earth Pledge Foundation describes intensive green roofs as those that "can be utilized as real roof gardens... [They] generally require an underlying roof structure with high load bearing capacity, in order to support the weight of deeper growing medium and larger plants. With a growing medium depth of 8" or more, intensive roofs can accommodate a wide range of vegetables, shrubs, and sometimes even trees." Extensive green roofs, according to Earth Pledge, "require only a few inches of growing medium (2.5 to 6 inches) and little additional irrigation beyond rain. Typically, these roof meadows are composed of plants like sedums, grasses and wildflowers-plants that can thrive in a rooftop environment with limited water, shallow roots and sparse nutrients."

Intensive Green Roofs are, by their very nature, more costly and demand more maintenance than their extensive counterparts. The hard costs for Calhoun's Green Roof—not including design services—were approx. $60 per square foot. Architect's and structural engineer's fees were additional because the Green Roof was not part of the original project, and it required some structural modifications.

In comparison, FXFowle Architects says that material and installation costs for a roof without irrigation and with a 4-6" soil depth (sufficient to support some non-turf) might run $25 per square foot (but it's important to remember that each case is different.) An existing building must be tested for stressing and may need to shored up. Many New York City buildings built after 2000 may be fine, depending on the soil depth desired.