The Beinecke Rare Book & Manuscript Library at Yale University, designed by Gordon Bunshaft of Skidmore, Owings & Merrill, is a modernist masterpiece. Its rectangular volume is enclosed in sheets of marble, thin enough (at 13∕8") to transmit light. That means the interior of the building glows by day. But it also posed “a major challenge,” says Bill Mahalko, who, as project architect for Chicago’s HBRA Archi­tects, oversaw a 16-month, $70 million renovation of the building. New Haven’s Newman Architects was architect of record.

“The thermal qualities of the marble are similar to those of single-pane glass,” says Mahalko. “It’s not a good insulator.” In cold weather, condensation formed inside the building, which houses some of the world’s most precious volumes—including a Gutenberg Bible.