This year, Preservation Burlington’s annual homes tour takes walkers to five midcentury-modern dwellings. That may come as a surprise to people who still think of concrete façades and walls of windows as “new.”

“A lot of people, when they think of a historical building, they think of a Victorian house,” says Devin Colman, a historic buildings specialist at the Vermont Division for Historic Preservation. “It has to be big; it has to be old; it has to be fancy. All those factors are the opposite of modernist design.”

But, while they’re certainly modernist, most buildings in the “modern” style “are 50 or older,” says Colman. Not only are they aging, but, with their expanses of single-pane glass and uninsulated walls, few of them meet current standards of energy efficiency.

Preserving those buildings is the focus of an all-day symposium at the University of Vermont on Friday, the day before the tour. Colman, who organized it, says the speakers will spend the first half of the day discussing why modernist buildings should be saved and the second half addressing how. “In the ’50s,” he notes, “the cost of energy was not a concern.” The problem is “how to make the building more efficient without destroying its historical integrity.”

Not so long ago, perhaps, many Americans would have been happy to embrace ornate older styles and let stark modern buildings decay. But Colman says the tide is turning against the equation of “modern” with “ugly.” Does that have something to do with the success of “Mad Men”? Sort of, says Colman: “It’s really a generational shift.” Popular culture has embraced the mod design aesthetic, he points out: “In car commercials, nine out of 10 of them, the car is driving past a sleek, modernist house.”

Still, modernist architecture in Vermont? When he mentions his field of expertise to locals, says Colman, “I get a blank look. Like, What, two buildings? But,” he says, “it’s all over the state; it just hasn’t been identified and recognized yet.”

One person who’s working on changing that is Glenn Andres, a Middlebury professor of the history of art and architecture who’ll speak at the symposium. He’s been working for the past 15 years on the Vermont volume of the Society of Architectural Historians’ Buildings of the United States series. One of the project’s challenges, Andres writes in an email, “was identifying significant buildings of the past 50 years (which do not appear in historic inventories because of their young age).” But, when he did begin to survey local modernist buildings, Andres became “painfully aware of [their] vulnerability.”

So, where are Burlington’s modernist treasures? You’ll have to go on Saturday’s tour to learn their addresses, though Colman notes that “two were designed by [Vermont architect] Marcel Beaudin” and another emulates the Frank Lloyd Wright style. While those are residences, Andres offers a list of some public modernist structures, including St. Mark’s Church, St. Paul’s Cathedral, Cathedral of the Immaculate Conception and the Chittenden Bank in Burlington; and campus buildings at Bennington, Goddard and Putney.

Then there’s the Preservation Burlington tour’s home base on Shelburne Road, a structure so familiar to Burlingtonians they probably don’t look at it twice: The former gas station became The Spot. Colman calls the café’s striking triangular canopy “classic modern design.”

When the gas station closed, he worried that “we’re gonna lose it,” he recalls — which is why the appearance of The Spot, with its appropriately ’60s-ish surfing theme, strikes Colman as a good omen for mod in Burlington. “It shows that these buildings can be reused,” he says.