Todd Miller and Brian Duis were moving back to Minnesota from Colorado, and house-hunting near the Minneapolis lakes and downtown.

"We were looking for modern architecture," said Miller. "For its open spaces, lots of windows and the way every square inch is used."

Their real estate agent was clicking on house photos — and skipped past a photo of a quirky boxy structure with zero windows on the street side, noting that it was just 2,300 square feet.

"We told him, 'We like boxes,' " said Miller. "And we don't need a lot of space."

When the couple stepped inside that midcentury modern flat-roofed box in Golden Valley, they didn't know it was a noteworthy one-of-a-kind residence.

"It felt like we were floating above the gardens," said Miller. "And there was so much glass."

That's because the main level — framed by four pairs of sliding doors — is cantilevered out over the recessed basement. Duis was impressed with the layout's "good flow."

Finally, Miller and Duis knew they couldn't pass it up after hearing the sound of frogs croaking on the half-acre, densely wooded lot, only 5 minutes from downtown Minneapolis.

Book-worthy design

In fall 2015, the couple moved into their new split-level home, and discovered that its cutting-edge design had recently been showcased in an eight-page spread in Larry Millett's book "Minnesota Modern: Architecture and Life at Midcentury."

Architect Richard Babcock had designed the modern cube on a big suburban lot for his family in 1961.

Babcock devised that striking windowless facade for ultimate privacy — rather than opting for curb appeal or impressing the neighbors. However, there are windows facing the private side and backyard, plus a screen porch that projects out over the landscape.

Babcock and his wife, Dorothy, lived in the house until 1998, and sold it to their daughter Lea Babcock Scherer and her husband, Jeffrey Scherer, a partner in MSR Architects. The Scherers made subtle modifications to preserve the home's historic character, before selling it in 2013 to owners who also valued the 1960s modern aesthetic.

"Finding out that we were living in a midcentury gem made us appreciate the house even more," said Miller. "We didn't want to do any radical changes that would make Richard Babcock cringe."

But the couple did want to improve the home's energy efficiency, add a master bathroom and home office, open up the living areas, and update and refresh the more than 50-year-old kitchen and other interiors.

Architects Lars Peterssen and Brent Nelson, of Peterssen/Keller Architecture, came up with a design plan to accommodate the owners' 21st-century lifestyle — without adding any square footage to the original 1960s footprint.

Respectful redesign

"I love this house," said Peterssen. "It was really exciting to update it — yet be respectful of the original architecture."

The remodeling project involved scores of improvements, from applying spray-foam insulation to all new lighting.

The Peterssen/Keller team converted unneeded storage rooms into smart functional spaces that Duis and Miller use every day, such as a master bathroom and a drop zone/laundry area.

"We're fairly minimalist in the way we live," said Miller. "We don't keep or collect things."

For the remodeled kitchen, they tore out a free-standing cabinet wall that was blocking natural light and views, between the kitchen and dining area. This move created space for a big quartz-topped center island.

They replaced the dated greenish-oak cabinets with Italian high-gloss versions with sleek integrated pulls.

"I did feel a little bad about the cabinets," said Miller, "but the new ones better maximize storage space."

A grayish-blue Heath tile backsplash "makes a bold geometric statement," said Nelson, "yet fits with the period of the home."

To keep the clean, unbroken lines, Nelson chose a flush range hood concealed in the ceiling and turned on by remote control. Luckily, the 1960s terrazzo floor was intact and merely needed polishing.

The adjacent living/dining area boasts three large sliding glass doors — "an economical way to get a glass wall back then," said Nelson.

After replacing all the tired oak ceiling trim with rich walnut, the men added a floating leather-faced and steel credenza hugging the far wall. A black leather Eames chair and vibrant artwork complete the midcentury modern vibe.

Since Miller and Duis both work from home, they finished off the basement, carving out a large home office and TV/family room.

A custom two-sided cabinet that Miller requested after seeing a similar one in Dwell magazine serves as a functional divider between the home office and family room.

"The individual boxes were built off-site and put together like a puzzle," he said.

Down the hall, they converted a closet into a compact sauna. "I love to set the timer on the sauna to heat up and be ready for when I return after a wintry outdoor run," said Duis.

While contemplating contemporary updates, Miller and Duis were never tempted to add a window on the street side. There's still that sense of mystery of what's inside the box.

"You can tell that Babcock's heart and soul went into designing this house," said Miller. "It feels good that we maintained that."

Peterssen also marveled at Babcock's ahead-of-its time design.

"Lots of homes being built now are boxes on boxes with big expanses of glass," he said. "It's amazing for 1961 how they got it right."

Lynn Underwood • 612-673-7619