The atrium incorporates a cafeteria and auditorium, as well as a number of mezzanine levels that can be used for functions. It also features an 8m x 22m sculptural water feature, designed by glass technologist James Carpenter, whose work with light and glass can also be seen at another recently completed landmark New York address, Skidmore, Owings & Merrill's 7 World Trade Center.
Icefall, as it is titled, is made from hundreds of glass prisms cast from Tasmanian sand, which has a low iron content and makes the glass resemble white ice. The cascading water, and the movement of people up and down the escalators that traverse the waterfall, help to animate the space.
In keeping with the sustainable design parameters, rainwater collected from the roof of the building is recycled for use in the sculpture. Rainwater is also used to replace water lost to evaporation in the office air-conditioning system, and is used to irrigate plants and trees both inside and outside the building. It is anticipated that rainwater will account for half of the water used.
Recycling applies to other materials as well more than 85% of the steel in the building is recycled. Further environmental savings were made by using concrete cast stone on the facade rather than traditional limestone panels, while other green initiatives include the use of low-emission glass on the curtain wall. This blocks the invisible solar radiation that causes heat gain.
In conjunction with the glass, Hearst has installed light sensors that control the amount of artificial light available at any given time. To maximise energy efficiency, lights and computers turn off automatically when a room becomes vacant.
Foster says the triangulated structure has the advantage of allowing more natural light into the interior than in a conventional office tower, thus contributing to the anticipated 23% overall energy savings. The number of internal walls has been minimised to further maximise the daylight. Carbon dioxide sensors also contribute to the building's energy efficiency and are linked to a demand-controlled ventilation system.
Other environmentally friendly features include the use of low-vapour paints and formaldehyde-free furniture. Concrete surfaces are finished with low-toxicity sealants and, in a further nod to ecological conservation, the floors and ceiling tiles were manufactured with recycled content.