New York, NY

Chelsea Green on Track as First LEED Version-3 Gold Certified Multi-Residential Development in U.S.

Just a few blocks from the High Line, the now-famous restored elevated railway bed that today sports pedestrian walkways amid a landscape of greenery chosen for its hardiness and sustainability, a 14-story building is rising in New York's historic Chelsea neighborhood that promises its future residents a better way to live.

With more than 90 percent of its 51 units sold before it had climbed above street level, Chelsea Green is a 14-story, luxury condominium from Alfa Development that is putting wellness and the most advanced and state-of-the-art systems, front and center to maximize energy efficiency, resource conservation and indoor air quality.

Every aspect of the 74,000 square foot concrete structure is designed to consider its impact on the environment, notes Alfa, which believes it could be the first LEED Version-3 Gold certified project in the U.S. LEED attributes are found everywhere – from the cabinets to the heating and cooling systems, the rainwater irrigation system and the green roof. To ensure ultimate efficiency, LED lights have been mounted throughout the building and solar shades installed above the windows. In addition, Schöck Isokorb® Type CM thermal break connections are being used in the balconies on the 11th through the 14th floors to further enhance the building's energy performance.

Recently approved by the NYC Department of Buildings, the 52 concrete-to-concrete Isokorb® modules are being installed on ten, 7 ½ X 16 foot balconies at Chelsea Green; provide a solution to one of the most critical areas of energy loss in building construction: thermal bridges. These breaks occur whenever there is a penetration of the building's envelope. It is the first project in New York City to incorporate concrete structural thermal break elements, which are recognized worldwide for their effectiveness, but are relatively new to the U.S.

Each balcony at Chelsea Green is cantilevered out 7 ½ feet on 8-inch-thick tapered concrete slabs. "Traditional balcony attachments deal primarily with only the structural cantilever and as a result transmit exterior temperatures to the interior floor slabs, adding to the energy use of the unit," said Frank Mattiello, Senior Project Manager at Alpha Development. "This thermal bridge effect can be felt when walking barefoot in one's apartment, even when the heating or cooling systems are in operation."

Isokorb® type CM provides load-bearing thermal insulation for these slabs and transfers bending moment stress and shear forces. Its integrated hanging and tensile reinforcement mitigates the use of other costly elements like stirrups or hooped mat. "Their modular configuration enables simple installation and submittal design," Mattiello added.

In a recent post to Schöck's blog, Omalawa Abdullah-Musa of Stephen B. Jacobs Group, Chelsea Green's architectural firm noted, "This is a major breakthrough for combating thermal bridging in New York City residential buildings. The process for getting this product incorporated into the project was challenging, since it was relatively unknown to most structural engineers here. Chelsea Green has set the tone for future projects and we are looking forward to working with Schöck and spreading the word about this innovative technology."


Project: Chelsea Green, 151 West 21st Street, New York, NY

Architect: Stephen B. Jacobs Group

Structural Engineer: WSP Cantor

Construction Company: DJM Construction

Products: Schöck Isokorb Type CM

Start of construction: Winter 2011

End of construction: Planned for Summer 2013

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