Originally, the design called for curved, insulated (double paned) glass panels, but these were found to be prohibitively expensive. Flat, insulated glass had been suggested, but was dismissed by Jahn. Single-paned (non-insulated), curved glass panels were eventually used, and resulted in the need for a more expensive air conditioning system, which remains very costly to operate, and is insufficient on hot days; internal temperatures have reached as high as 90 °F (32 °C). The building is also bitterly cold in the winter; in its early years, ice formed on the interior of some of the wall panels. The marble floor of the atrium initially developed unsightly water stains, an issue which has since been resolved.