In Rural Minnesota, a 70-Acre Lab for Sustainable Living Paul Hunt still remembers the dilemma that he and his wife, Lynn, faced in early January 2010 at their home in rural north-central Minnesota. The couple had just moved into their ultra-efficient house, on the outskirts of Pine River, population 944, but still lacked a thermostat and were about to go out of town for more than two days. It was bitterly cold, and an exterior sensor, one of the many dotting their house, suggested that the nighttime temperature would dip far below zero. Should they leave the heat on or turn it off? As a former Minnesotan, I can say without hesitation that this is not a difficult midwinter decision for the average homeowner. Neither the Hunts nor their home are what you'd call typical, however. Their decision to leave the heat off - despite a low of 32 degrees below zero Fahrenheit on Jan. 2 - was vindicated upon their return home, when they found that their interior had remained a reasonably comfortable 66 degrees. In the midst of Minnesota's scenic lake country, the Hunts have assembled an eclectic mix of buildings on a 70-acre campus, including their own airtight super-insulated house. A separate administrative building called Old Main, constructed from straw bales and adobe-like cob, features a dragon and hanging bats carved into one exterior wall and a bathroom festooned with Egyptian hieroglyphics. Nearby, a manufacturing space of nearly 14,000 square feet known as the ManiShop boasts a spacious built-in greenhouse and what may be the largest glazed hot air solar panel array in all of North America. Within this laboratory of energy-efficient housing, the Hunt Utilities Group, or HUG, mixes high-tech ingenuity with homespun practicality and a touch of whimsy in its drive toward what Mrs. Hunt laughingly dubs "decadent sustainability." She may have the immediate goal of luxuriating in a guilt-free solar panel-heated bath. But the company she started a dozen years ago with her husband is angling for a far bigger payoff. In the long-term, HUG hopes to construct homes that heat and cool themselves, feed their occupants and recycle all of the nutrients through integrated composting techniques. If the end goal seems idealistic, the Hunts were cheerfully pragmatic during my recent visit to a campus that puts them within walking distance of Pine River's compact downtown. The company has grounded its expectations in the clear-eyed requirement that all methods must prove their mettle in Minnesota's often-brutal winters or be discarded. HUG's dozen or so employees have systematically experimented with heating and air exchange systems and windows, for example, and designed and built some of their own components when others aren't up to snuff. The campus also houses two nonprofits: the Rural Renewable Energy Alliance, which focuses on making solar power more accessible, and Happy Dancing Turtle, which promotes sustainable living through practical hands-on programs. The like-minded tenants have all benefited from the technological wizardry of Mr. Hunt, who founded Hunt Technologies in the mid-80s and patented an ultra-narrow bandwidth communication system that allowed utilities to use devices called "turtles" to remotely read data from electric power meters at homes and businesses. Borrowing a few ideas from that technology, Mr. Hunt has blanketed the Pine River campus with a data- measuring system dubbed HUGnet. "The whole place is a lab," he said during my visit. The system, which includes more than 1,000 sensors placed at strategic points on the buildings, collects parameters like temperature, wind speed, pressure and humidity every five to 15 minutes. "We need to know what works and what doesn't so the next design gets much better," Mr. Hunt said. The data are publicly available on the Internet, meaning that anyone can track the temperature fluctuations beneath the Hunt's kitchen table, on the floor of their combination root cellar-storm shelter, or at the east end of their built-in greenhouse. The Hunts stress that whatever ultimately emerges from their housing laboratory must be readily affordable while measuring up to their standards, and they have begun working with an architect to help design a culturally sensitive prototype for Indian reservations. Bob McLean, HUG's chief operating officer, said that the company also has been heavily involved in regional sustainability efforts, including the federally financed Central Minnesota Sustainable Development Plan. The blessing of the Cass County Board of Commissioners, has been critical to HUG's success, Mrs. Hunt said. Before buying the property, the couple approached the county board for permission to bend or break some building and sewer codes so they could experiment with how to improve upon them. The county not only agreed, she said, but told her and her husband that they should do even more to break the rules. Signs of the company's prolific experimentation are now everywhere on campus. The Hunts have tried out different types of solar panels and composting toilets, while a plus-size worm composting bin in the ManiShop's greenhouse allows the workers to recycle their lunch leftovers. Large methane digester tanks huddle in a corner of the Hunts' spacious garage for another research project on treating household sewage and using plants to filter the effluent. Not satisfied with the insulating potential of existing window options, the company designed a double-window setup for the Hunts' home with a foot-wide sill separating the layers. In a rental duplex across campus, the company's construction manager, Dug Swanson, is overseeing a trial of multiple window designs that are getting a rigorous real-world tryout in winter weather. By applying the lessons learned in building an initial stand-alone rental unit next door, Mr. Swanson said, HUG was able to cut its per-square-foot construction costs by nearly half for the duplex. The Hunts weren't shy about pointing out what materials and methods that didn't make their performance cut. Although clearly proud of their quirky administrative building, with its artistic flourishes, three-foot-thick walls and low energy consumption, they readily discussed the building's energy performance flaws. And the straw bale and cob technique, often a patience-trying labor of love, proved so work-intensive that they've ruled it out for their other construction projects. Mrs. Hunt said the wind turbine near the main entrance makes a great calling card, but that the area's variable and generally modest winds have limited the turbine's contribution to overall energy production. And although the ManiShop boasts a no-maintenance green roof, the Hunts said they'll probably exclude that feature as well from future buildings. By including other design elements, they found, the green roof isn't needed to prevent heat loss or water runoff, while the structure required a massive support system to keep the ManiShop's roof from collapsing during a heavy snowfall. Built-in south-facing greenhouses are a signature of HUG's design work. The lack of natural daylight in the winter months, though, has made the greenhouse in the ManiShop more suitable for ornamental plants than for produce. For now, the Hunts have been growing fruit and vegetables in a three-acre garden surrounded by an eight-foot-high deer fence, another requirement in Minnesota. The garden produced its first harvest this past summer and fall, distributed mainly among workers. So far, HUG's heating systems have offered one of the clearest signs that the company is on the right track. Within the ManiShop, an air-exchange system directs the greenhouse's 95-degree air near the ceiling to the large array of solar panels. The panels warm the air to 140 degrees before pipes pull the heat into a giant underground battery formed by a 10-mile-long network of corrugated pipes buried in sand beneath the building's foundations. The ManiShop, in particular, has scored particularly well on the Home Energy Rating System, or HERS, program, with a rating of 12 (more than eight times as efficient as a standard new home). The Hunts, though, have tailored their arguments for cost-conscious consumers. Mrs. Hunt told me proudly that the monthly cost to heat the 13,790-square foot building averages only $85.54, tax included. And there are other wintertime considerations. The element that you don't think about every time is, how fast does it pay back when your pipes don't freeze? Mr. Hunt said. And it's not an emergency if your heater fails or if the electricity goes out. Last January was unusually mild, at least by Minnesota standards, and Mrs. Hunt rarely had to turn on her home's heat at all. "When I get cold, I let the grandchildren come over and play and they heat up the house," she said, with a smile.