LE SUEUR — Bruce McKay became enamored with green before it morphed from a mere color into a societal imperative.

“My interest in sustainable energy started in the ’70s,” the 50-year-old electrical engineer said. “And over the course of years I read all the books I could get my hands on.”

As he talks he stands in his rural Le Sueur home that serves as a culmination of that abiding interest.

The structure he and wife Deb have built is a vanguard example of how to live off the sun. The 36-feet by 120-feet dwelling is a solar energy test lab of sorts with intermingling technologies throughout.

“Many different pieces of the puzzle have been brought together for this,” Bruce McKay said. “I don’t know of a place where all the different pieces are put together in one building.”

The house, on a 40-acre site, was recently featured on a statewide tour of solar-powered homes and businesses.

McKay said dozens of visitors went through the unfinished house to get ideas on how they might similarly heat their homes with the sun.

The home’s genesis began several years ago, when McKay was on a solar tour himself and met Minneapolis architect Richard Venberg.

Venberg was hired to design the home following the McKays’ exhaustive search for a suitable site to build upon.

McKay said 1,500 properties in Minnesota and Wisconsin were considered during a five-year period before the couple settled upon the Le Sueur County site.

McKay is doing about 75 percent of the work on the house, and though its living quarters remain works in progress, the home’s solar power infrastructure has been operational since August 2007.

McKay said the house easily passed its heating test last winter with a propane-fueled hot-water heat backup system receiving only limited use.

He said that backup system will become a backup itself when it’s replaced by a Finnish wood-burning masonry heater that can produce 18 hours of radiant heat from a one-hour fire.

In building their one-level home, the couple purposely eschewed adding a basement, where heat storage tanks are typically located in a solar power dwelling.

The no-basement issue was solved by adding a below-grade sand bed that runs the length of the house.

Tubing installed into the 2-foot-deep bed carries water heated by 14 solar panels on the roof. McKay said the sand holds heat longer than water tanks.

Heat is radiated through the floors of the home, ensuring virtually even floor-to-ceiling warmth. A computerized system controls 24 temperature points in the house.

Walls of the home are of an insulated material that uses engineered “Lego” blocks comprised of 85 percent recycled polystyrene (coffee cups, packaging peanuts) and concrete.

McKay said he continues to tweak things as he goes along to make the house even more energy efficient.

He figures the system will pay for itself in saved electricity costs in eight to 10 years.

McKay has also embarked upon a project with potential business applications — he wants to engineer space-efficient solar power units whereby homeowners would be charged a nominal installation fee to rent the system.

Solar power’s time has clearly arrived for the couple, but McKay is unsure of when it will become the norm in American homes.

“People usually stay in their normal ‘path’ until something makes them change.”

And when the cost of conventional home energy becomes prohibitive for the masses, change will follow, he said.