text: The tower and its annex have similarly-designed facades. The facade is made of anodized aluminum and reflective glass panels. Each facade segment measures  and consists of both glass panes and aluminum plates. To conserve energy, each window is double-glazed; the inner pane is coated with chrome plating. The windows on each floor are separated by flush aluminum spandrels. The spandrels were manufactured by Flour City Architectural Metals, a firm based in Glen Cove, New York. The aluminum is silver-colored, like that on the Pepsi-Cola Building and One Chase Manhattan Plaza, because Stubbins thought a dark color would not allow observers to "see the shade and shadow". The facade is fitted with  of insulation, double the amount of insulation considered normal at the time of construction. The aluminum was polished to reflect heat from sunlight.
  Roof
  The triangular roof of the Citigroup Center rises  above the top story and faces south, sloping at a 45-degree angle. The roof was originally intended to face west and contain several terraces, but the architects rotated the roof southward to accommodate flat-plate solar collectors, which they believed would produce hot water that could dehumidify air and reduce the need for other energy for cooling. Starting in February 1975, engineers from the Massachusetts Institute of Technology conducted a twelve-month feasibility study for the installation of such a system. Afterward, the system was scrapped, either because of the smaller-than-expected savings, the cost of the required refined mechanical systems, supplier issues, or the insufficient energy produced by the system.
  Even after the solar-collector plans were scrapped, the design was kept; Stubbins wrote that the roof "relieves the uniformity of flat-topped towers proliferating in the center of the city". This made Citicorp Center the first postmodern skyscraper in New York City with an entirely decorative roof. The roof was also fitted with solar panels in 1983, when Consolidated Edison and Citibank sponsored a four-year solar panel test.