When the 7-year-old Hanson twins want to spend time with their grandparents, they no longer have to travel to Louisiana. Now Grandma and Grandpa live just a few feet away.

“In Louisiana, we only saw them a couple times a year,” said Zelie. “Now I can visit them every day,” said Solveig. “They’re right downstairs.”

That’s because the girls’ parents, Jen and Scott Hanson, decided to include a spacious apartment inside the modern, energy-efficient house the family recently built in Golden Valley.

From the street, the striking blue house with two gables looks like a single-family home. But tucked underneath is another 1,000-square-foot residence.

The Hansons were in the design phase of their project when Jen suggested that her parents, Paulette and Bob Carlin, consider moving to Minnesota. The timing was right. Paulette was about to retire; Bob, who has a rare disease, was no longer working. Why not live near their only child and grandchildren?

“Might as well be with family,” Paulette reasoned.

Soon, the plan to move to Minnesota evolved into a plan to move into the Hansons’ house.

“It only makes sense,” Scott said. “Jen’s a nurse, and over time, we’ll be able to help out her parents.”

A desire to help aging parents is just one of the factors driving today’s multigenerational housing trend, which is on the rise in the United States. In 2016, a record 64 million Americans — 20 percent of the population — lived in multigenerational households, according to a Pew Research Center analysis of census data. That’s up from 51.5 million people and 17 percent of the population in 2009.

The Hansons’ architect, Tan Nguyen, principal of Nguyen Architects, Minneapolis, said he’s heard a lot more talk about multigenerational living among clients in recent years. But the Hansons’ project is the first he’s designed for precisely that purpose.

Once it was agreed that the Hansons’ new home would house not two generations but three, Nguyen reworked the plan.

The Hansons hadn’t originally intended to put in a full basement — just a partial one where Scott, a self-employed electrician (Verdant Electric) could have a workshop and store his tools and wiring. The 2,500-square-foot, one-level floor plan was all the living space the family needed.

But once they decided to make room for Jen’s parents, they decided to explore the possibilities of all their potential square footage.

The Hansons’ sloping site in North Tyrol Hills lent itself to a walkout lower level. Nguyen designed a self-contained apartment with an open kitchen/living area, a wheelchair-accessible bathroom, laundry facilities, a pantry, a private patio and even an elevator.

“The way we did the elevator, they can go out of the house without going through the upstairs,” said Nguyen, who, as owner of Bristol Built, was also the Hansons’ contractor. The unit has double doors that open to the garage.

“We included an exterior door, so it could feel like an apartment,” Jen said.

‘Almost net zero’

Energy efficiency was a high priority for the Hansons. With that goal in mind, their home has extra-thick exterior walls, solar panels and a photovoltaic system, triple-pane windows, LED lighting and spray-foam insulation, resulting in a home that’s “almost net zero, and can run off the grid,” said Nguyen. (The home’s HERS — Home Energy Rating System — score is 12; a standard new home is about 100.)

The insulation serves a dual purpose. While it adds to the home’s energy efficiency, it also serves as a sound absorber between the two separate households.

“We all want privacy,” Scott said. “We tried to insulate the ceiling so noises don’t carry.”

Jen, a fan of midcentury modern design, initially wanted a flat roof. “But it doesn’t look good with solar,” she said. “We did a midcentury modern feel inside.”

The floor plan is open and casual, with a big family-friendly kitchen/dining/living room. The girls share a bedroom, with trundle beds for sleepover guests, a playroom and, between the two rooms, a Jack-and-Jill bathroom. The playroom is important, Jen noted, since they don’t have basement space for the girls’ toys and activities.

Finishes include hickory flooring, a walnut accent wall in the front hall, vertical-grain white oak cabinets in the kitchen and a modern blue-tile fireplace in the living room.

The home’s low-maintenance exterior includes fiber-cement siding and trim made of recycled fly ash, a material that doesn’t absorb water. The low-maintenance deck is made of recycled PVC. The landscaping includes a rain garden, a pollinator garden and a plot near the lower-level apartment for Paulette, who enjoys gardening.

‘Team effort’

During construction, Paulette came up from Louisiana to choose finishes and fixtures for their future home.

Jen said, “She found the lights. She picked the floors. It was a team effort.”

Then, the Hansons moved into their new home, and the Carlins prepared for their move north.

“We sold the house, got rid of everything we owned,” said Bob, keeping only a few antique furnishings, some artwork and a shell collection from Mexico that Bob, a science buff, wanted to share with his granddaughters.

Then in May, soon after Paulette left her job, she and Bob moved into their new home. “We were all nervous,” Jen said.

It was a huge life change for her parents. “She [Paulette] retired and moved to another state in one month.”

And Jen wondered about the day-to-day realities of multigenerational living — “the unknown of what it would be like.”

“I wasn’t nervous,” said Paulette, although she admitted that spending winters in Minnesota “was a concern.”

After several months under one roof, life is running smoothly for this multigenerational family.

Paulette and Bob help with child care and pet-sitting for Maggie, the family bulldog.

“We’re happy to do it,” Paulette said.

Bob has access to better health care than he did in Louisiana. “Jen being a nurse, she’s been finding a lot of medical help for dad,” Paulette said.

It’s working, in part, because everyone has agreed to some ground rules for having two households in one house.

“We like privacy and boundaries,” Jen said. The girls have been taught to knock or text when going to visit their grandparents — not just burst in.

Paulette returns the favor. “If I need to go up there, I text, ‘OK if I come up?’ ” she said.

The family also sought legal counsel upfront — “to make sure everything is fair,” Jen said.

The Carlins paid for some of the materials in their unit, and also help pay for utilities, while the Hansons own the home and paid for its construction.

“So far, so good,” said Paulette. “It’s been very comfortable. They planned it really well, and fixed it to our liking.”

And after 20 years of living in different states, she’s enjoying time with Jen and mother-daughter outings, such as seeing “Mamma Mia!” live.

“I like being with everybody … the girls,” Paulette said. “The best thing is the family ambience.”