Green Roof FAQs

What are the environmental benefits of a Green Roof?

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.

Has Calhoun been able to measure its energy savings since the installation of the Green Roof?

It would be hard to compare energy savings pre- and post-Green Roof, since the roof was installed simultaneously with the addition of four new floors - almost doubling the size of the school. But the business office is continually monitoring our progress, and the school is now looking to add solar panels to further contribute to energy savings (see #7).

How have teachers incorporated the roof into curriculum?

The lunch program has been a major beneficiary of our Green Roof herb garden, which is planted each spring as a joint project between Lower School classes and our food service chefs — who frequently visit classrooms and conduct after-school clubs to promote nutrition and healthy eating habits.

Lower School students are engaged in worm composting, which provides fertilizer for the gardens. The Green Roof Learning Center is also used by teachers for environmental and plant biology studies as well as for units in math (geometry). The Green Roof has also been the site of an outdoor art installation and various receptions, a source of inspiration for poetry classes, and a favorite escape from urban life!

The popularity and success of the Green Roof was certainly a significant factor in the selection of "Go Green" as the school's 2006–07 yearly theme, which launched added and continuing awareness to our sustainability initiatives.

Does the school have any other plans in progress?

Solar Panels: The school has researched the possibility of installing a Solar Panel System. While the scale of what is possible wouldn't provide much in the way of energy savings, we hope that the use of the solar panels could be incorporated into the school's science curriculum.

What words of encouragement would you offer other school administrators who may be unsure of how to begin making changes in their schools — or are unsure if spending the time and effort to go green is really worth it in the long run?

Says Head of School Steve Nelson: "The Green Roof added some cost to the overall expansion of our 81st Street building when compared to a utilitarian membrane roof, but it was actually the least expensive educational space we built as part of our four-floor expansion. Beyond the invaluable educational uses and considerable benefits to the environment, the positive public attention and good will generated by responsible architecture have returned our investment several times over. Plus, long after our capital campaign ended, the Green Roof continues to inspire philanthropy."

Has Calhoun's Green Roof been well received beyond its own community?

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.

When did Calhoun build the Green Roof and what were the motivating factors in doing so?

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.

What kind of Green Roof did Calhoun install?

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."

What were the costs involved in building Calhoun's Green Roof?

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.

Green Roof engineering
Tours & Information

Tours of the Green Roof are open to the public—particularly educational and governmental groups, local residential and community groups.

Please contact:
Beth Krieger
Director of Communications

Main Building 3rd - 12th Grades 433 West End Avenue New York, NY 10024 212.497.6500

Robert L. Beir Lower School Building 2.8 Years - 2nd Grade 160 West 74th Street New York, NY 10023 212.497.6550

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