What is now the Smithsonian’s Cooper Hewitt design museum was once Andrew Carnegie’s home. A renovation has added exhibit space and made it a better showcase for design’s evolution. (Cooper Hewitt, Smithsonian Design Museum/Cooper Hewitt, Smithsonian Design Museum)

Since 1976, the Smithsonian’s Cooper Hewitt museum in New York has been housed in one of the most glorious mansions from the city’s most glorious age of wealth and extravagance, the 1902 home of Andrew Carnegie. And the problem has always been: It’s the wrong kind of glory.

The mansion was given to the Smithsonian by the Carnegie Corporation, the charitable organization established by the steel magnate, to house a collection of objects that has never quite seemed at home amidst the opulence and grandeur of the neo-Georgian stone and brick pile on Fifth Avenue. The mansion is locked in a particular past, full of wood paneling, stained glass, carved ceilings and even a themed room full of ornately detailed Indian teakwood. The collection, however, is an ongoing study in design evolution, spanning centuries, but fundamentally preoccupied with ideas of innovation and contemporary problem solving. How do you display iPhones, designer furniture, state-of-the-art wheelchairs and the latest in thermostat technology in a building that feels more Downton Abbey than Silicon Valley?

On Dec. 12, the Cooper Hewitt will unveil its latest effort to make its capacious home more amenable to its basic mission, an $81 million project to renovate, refurbish and rethink the design center for the future. Exhibit space has been increased by 60 percent; new cases have been designed by the go-to firm of Diller Scofidio + Renfro; a new public staircase and freight elevator have been added; all systems and amenities have been updated, including a cafe and book store; and exhibit designers have reconceived the display of the entire collection, including a much buzzed-about new “pen” that allows visitors to download exhibit information and interact with digital tables, creating a unique online record of their visit.

Visitors will notice one major change immediately upon entering the mansion’s main hall on the first floor. To the left a visitor services desk, designed by Diller Scofidio + Renfro, has an aerodynamic sleekness, and soft lines distinctly at odds with the coffered ceiling and oak woodwork all around it. But for all its pleasing dissonance, it is a minimal intervention: Whenever necessary, including during large social functions, the entire desk can be slid back behind an enormous 2,000-pound “secret” door discreetly hidden in the paneled wall. This prominent detail sets a pattern for the rest of the redesign: Wherever possible, the old home feels like an ornate frame that contains an intriguing but ephemeral sense of the contemporary.

Most of the mansion’s two main floors, including much of the space used by Carnegie and his family in the regular course of life, retain their historical character. Display cases have been cleverly designed not to block windows, and signage and text have been carefully fitted into the sumptuous interior without seeming discordant or disrespectful. What’s new feels more like a self-conscious overlay of contemporary design rather than an effort to finesse some kind of hybrid mix of new and old. As one former curator said of an earlier attempt to make peace with the mansion, “The house had such a big presence. The more you fought it, the more it disagreed with you.” The current redesign, led by Gluckman Mayner Architects with Beyer Blinder Belle assisting with preservation and historic issues, feels about as right as they are likely to get it. The space remains historic without being static, and there’s more coexistence than fighting between the house and the collection.

An artist’s rendering of the redesigned interiior of the Smithsonian’s Cooper Hewitt design museum. (Cooper Hewitt, Smithsonian Design Museum/Cooper Hewitt, Smithsonian Design Museum)

Less apparent to visitors, but essential to the ongoing vitality of the museum, are improvements to its basic function. Before the latest renovation, the museum was often compelled to close to visitors while installing new exhibits. Without a freight elevator, large objects were brought in and out through the front door, so the museum simply went dark during those days. Now it is equipped to stay open while curators swap out old exhibits for new. By moving collection storage to a facility in New Jersey, the museum has also gained some 7,000 square feet of new exhibit space. The second floor has been turned over entirely to showing pieces from the permanent collection while the third floor, formerly a library, is now an open and attractive gallery with 6,000 square feet for temporary exhibits.

The reopening of the museum will also mark the opening of 10 new exhibits and installations, including a “process room” that is designed to introduce visitors to basic design concepts and thinking and to pose questions that will structure their experience of the museum.

A visit late last month, while work crews and curators were racing to put the finishing touches on the interior and exhibits, revealed a Cooper Hewitt better positioned to compete with other institutions on Fifth Avenue’s museum mile, including the Metropolitan Museum of Art and the Guggenheim, just a few blocks south. The main third-floor exhibition hall, the museum’s first open-plan exhibit space, is given over to a show called simply “Tools: Extending Our Reach.” The show includes material from the Cooper Hewitt collection as well from nine other Smithsonian museums and collections. It was ambitious of the curators to attempt an exhibit that borrows so widely across other Smithsonian entities, but the results are worth it.

The space is large enough that the designers and curators are able to make both aesthetic and didactic statements, and so among the many objects, ranging over some 1.85 million years of history, is an installation of a sculpture by Damian Ortega, called “Controller of the Universe.” Borrowed from a private collection, the artwork consists of hand tools hung from the ceiling, as if they are bursting out from a center point like the Big Bang expanding the cosmos. If you stand at that center point, the effect is intoxicating: The tools seem to radiate power in all directions, flattering your own, and by extension humanity’s, sense of power over the world. But these are also sharp and potentially dangerous objects, and the feeling of power is double-edged.

It is an eclectic exhibit — full of patent models, drawings, electronic gimcracks, medical devices, space-age wonders and high-end digital toys — and that eclecticism is part of the design museum’s charm. It can afford to be a little looser in its curatorial ideas, a little more associative in its thinking, than other museums. At the heart of its intellectual mission is the transmission of a fundamental connection between work and pleasure. A well-made tool changes the experience of any task it serves. A beautiful corkscrew makes the opening of a bottle of wine contiguous with the experience of drinking it.

The “Tools: Extending Our Reach” exhibit conveys that idea abundantly well. Indeed, it seems exactly the sort of show that would be happy to live, for a while, in the now-empty Arts and Industries Building next to the Smithsonian Castle, where connections between scientific innovation and aesthetic expression were regularly explored more than a century ago. As the Smithsonian contemplates future uses of the Arts and Industries Building, the renovation of the Cooper Hewitt may well provide useful data and direction. If nothing else, the Cooper Hewitt project demonstrates the feasibility of creating a fashionably modern museum within a historic building without undue compromise to either the past or the present.

Unfortunately, the much-vaunted digital pen that allows visitors deeper access to the collection and a record of their visit wasn’t available to play with last month. Museum officials said production difficulties, not design issues, were to blame, and that the pen would be available early next year. So nothing can be said of its effectiveness except this: Conceptually, it seems well intentioned. Museums, today, are increasingly overstuffed with technology designed to distract the visitor from the experience of objects. But if the pen works as promised, it can serve a higher function, to consolidate the learning experience after the visitor has left the museum.

Design is a seductive topic today. For many people in the developed world, basic ideas about innovation and progress are experienced primarily through the aesthetics and small improvements of everyday objects, especially our digital friends and helpmates, including phones, games and computers. In one context — the economic realm where creative destruction is no longer deemed a necessary evil but an end to be cherished in and of itself — innovation may mean the perpetual destruction of the past, the loss of livelihoods, the uprooting of families and the decimation of the middle class. But when it comes to consumer objects, the Janus-face of innovation is all smiles and blandishment. This seems to be the reason that capitalism still functions, despite its heavy cost to the family, the environment and social structures; no other system produces such beautiful toys.

So perhaps that long-standing sense that the Carnegie Mansion is an odd place for a design museum isn’t so odd after all. A plutocrat of the industrial age built this house, while in many ways it is our own appetite for consumer goods that has helped build the collection and keep it vital. Anyone visiting the mansion cannot help but wonder: What did it cost to build all of this? Which is a question we should all turn on the objects that make our lives slightly more delightful: What is the cost of all this stuff?