ST PETER — The architect calls the home she designed for Jack and Mary Spear a “green aesthetic” that reflects what she’s all about.

The Spears just call it darn comfortable — but not in the manner of an Earth Mother sandal despite the home’s save-the-planet sensibilities.

“It’s not like a Birkenstock shoe,” Mary Spear laughingly said as she and her husband sat in their new airy aerie atop a hill just east of St. Peter.

The 2,600-square-foot home was built to be environmentally friendly in spades but not to the point of zealotry.

 Jack Spear said he’s not really interested in living totally off the grid, but the idea of such energy efficient living has intrigued him for years.

And when the time in the couple’s lives came to do something about it, they went full-bore. The result is a structure that will be one of the 14 homes featured on an upcoming statewide tour of selected architect-designed homes.

“It’s a modern design, but a modern design that’s comfortable to live in,” said independent Minneapolis architect Sarah Nettleton, who spent eight months on its design.

“I think people get turned off by modern. This is light and airy — a ‘loft in the country.’”

It’s also a polar opposite of the home the Spears lived in for 17 years in St. Peter. That was an 1875 house they completely renovated and thought they’d remain in for the long haul.

“We weren’t looking for anything. This just happened,” said Jack Spear, who works for a Le Sueur sand and gravel mining operation.

The couple’s transition began when a 14-acre plot of land its owner had intended as a retirement setting became available when the owner opted to retire elsewhere.

The Spears began talking and their vision began to emerge.

“We said, ‘If we build we’re going to use the latest practices to make this an energy efficient home,” Mary said.

The house features structural insulated panels in lieu of stud-construction walls, geothermal ventilation and the absence of something many people would find unthinkable — no air conditioning, at least  not in the conventional sense.

“But we’re not sitting around in a pile of sweat in our underwear,” Jack said.

The home’s hilltop location, ceiling fans and expanses of windows allow it to be air-cooled at night. Also, an underground air-handling system exchanges warm humid air for cooler, less humid air pulled in from large-diameter pipes buried to an 8-foot depth.

In winter, 25 percent of the home’s heating will come from passive use of solar power, with a small boiler in the basement serving as backup. The concrete floors radiate heat pumped through inlaid tubing.

Nettleton said the custom-made windows in the house offer four times the energy efficiency of typical windows. The home is virtually air-tight and its design eschews wasted space.  

“This house is compact and efficient. It doesn’t have extra rooms that no one will go into,” Nettleton said.

The annual Homes By Architects tour takes place Saturday and Sunday, with most of the homes in the Twin Cities metro area. For more information go to www.HomesByArchitects.org.