Their 1980s contemporary home was awkwardly laid out and had little room for homeowners Pat Matre and Miriam Goldfein to host their extended family for dinner every Sunday. And without a basement, the couple didn’t have a safe haven from violent storms rolling in from the west. Now with grandkids, they were even more concerned about safety.

“The front glass would shake, and the house would whistle,” said Matre. “We had nowhere to hide.” And then after a heavy rain, water unfailingly seeped into the crawl space and filled the low-lying yard. The home needed scores of upgrades, as well as a major remodeling.

So in 2015, the couple decided to start fresh and design a new multifunctional dwelling on the picturesque flat lot Matre had bought in 1994 on Lake Minnetonka’s Upper Lake.

The couple not only built the Tonka Bay residence exactly the way they wanted it, but they pushed the home’s innovative design, high-tech building materials and energy efficiency to the next level to make it “carbon-free and clean,” said Matre.

The result is a net-zero lakeside abode nestled on a narrow deep lot. It produces more energy than it consumes, thanks to a geothermal heating-and-cooling system and photovoltaic solar panels spanning a south-facing gable.

The couple installed four Tesla Power Wall units to store excess electricity. The stormwater is absorbed and filtered through two green roofs, rain gardens and a water-retention area below the deck.

Finally, the couple’s storm bunker is inside the attached garage, which is composed of thermal-mass concrete shielded by a garage door rated for 220-mph winds.

“We want to be good citizens of the planet and set an example,” said Matre. “I’m a leading-edge kind of guy and like to show that you can build a small net-zero house on a 50-foot-wide lot.”

The couple enlisted David O’Brien Wagner of SALA Architects after Matre had admired a Wagner renovation of a Ralph Rapson-designed residence.

“Ralph Rapson was thoughtful about how a home is integrated with the site,” said Wagner. “His soft modern style gives a sense of warmth, but with clean contemporary lines.”

Wagner took on the challenge of the lot sitting on a flood plain by designing a concrete plinth to raise the home’s floor 2½ feet. “It will be like living on a houseboat in a real flood event,” said Matre.

The 2,600-square-foot, three-bedroom home isn’t a full two stories, in order to blend with the scale of neighboring residences. “It gives us what we need, but doesn’t overdominate the site,” said Matre.

The home’s lake side boasts large, modern expanses of glass, but the traditional gable roof “creates a balance between a modern aesthetic and a humble cottage,” said Wagner. That south-facing gable also serves as a surface for the 40-panel solar array.

The exterior’s lower half is clad in corrugated galvanized steel, the top half in gray-stained cedar. And with the two flat green roofs, “it’s the unique gray duck on the lake,” said Wagner.

On the garage side, you enter the unconventional home in an unconventional way. Wagner designed a “boardwalk” enclosed by a cedar screen wall that guides you to the front door.

Beyond the mudroom and powder room is the big reveal: a 20-foot wall of glass facing Lake Minnetonka. You can hear the water lapping along the shoreline only 30 feet away. Phantom screens, which roll up and down, convert the great room into a huge screen porch.

From the kitchen, living and dining areas, “We can feel the breeze, and hear the lake, birds and kids playing,” said Matre.

Since the home faces west, automated shades can be drawn when the sunset gets too intense.

Goldfein and Matre also can see the treetops through a band of high clerestory windows, which let in light while providing privacy from the home next door.

The open and airy minimalist spaces are warmed by wide-plank white oak floors and Douglas fir trim and wall panels.

In the dining area, two custom-designed stainless-steel topped tables and a banquette can easily accommodate large gatherings for Sunday dinner.

In the adjoining kitchen, passionate cook Matre put in three wall ovens and an induction cooktop inserted in the granite-covered center island.

The brushed stainless-steel countertops and oversized Julien sink give it “the look, functionality and durability of a commercial kitchen,” said Matre.

In fact, the kitchen’s blue-themed color palette, including the rippling glass backsplash, is “evocative of being on the water,” said Wagner.

He compared the efficient design of the kitchen, living and dining areas — with multiple space-saving built-ins — to the inside of a yacht. “I packed high function and use into a small footprint,” said Wagner.

Today the main-floor guest quarters are used for visiting family, but universal design features and layout make it easily converted to an owners’ suite someday.

The couple were committed to building a home with accessibility, and added wide doorways, curbless showers and a ramped entry.

On the second floor at the top of the stairs, you’re greeted by yellow sedum sprouting on the green roof, visible through the clerestory windows.

“This is what we wake up to,” said Goldfein, referring to the sky and shimmering water on the other side of a massive triangle window inside the owners’ suite down the hall.

“We pulled windows around the corners for views up and the down the lake,” said Wagner.

He also designed a glass enclosure around the owners’ bathroom, which lets in light, making it feel bigger and “like stepping inside a glass cabinet,” he said.

Matre and Goldfein savor the sound of loons calling and watch the great blue herons on the dock at their Tonka Bay retreat.

But the choice to build a smart net-zero home with long-term livability is the most satisfying.

“Our home is sustainable in two senses,” said Matre. “It produces more energy than we consume, and we can grow old here and never have to leave.”