The Steyns’ off-grid home in Colorado.

When Phillip and Heather Steyn decided to build an off-grid house far from the beaten path, they settled on Structural Insulated Panels (SIPs) rather than stick framing, logs or straw bales. Today, two years later, they're certain they made the right choice.

Building a house with SIPs appears superficially like building a house of cards: in both cases rectangular units are stacked side by side with no additional framing members used. The difference—and it's a really big one—is that SIP houses don't fall over when your heavy-footed brother stomps into the room. Nor even, in the case of the Steyns' house, when the vicious north wind descends into the conifer forests of northern Colorado from the high plains of Wyoming.

Heather and Phillip Steyn

That's because SIPs are what the name implies: panels that are both structural and insulated. It's like buying pre-fabricated super-insulated walls, but a whole lot better. The idea of a SIP is simplicity itself: take two pieces of oriented strand board (OSB) and separate them with a filling of polystyrene foam. The result is as morphologically uncomplicated as it is conceptually elegant. Not only do you have a solid, highly insulated wall panel through which air cannot pass, you also have a structural unit built on the same principle as a truss or an I-beam, since compressing one part of a SIP tensions another (and vice versa), making the entire wall a monolithic unit stubbornly resistant to bending, flexing or sagging.

LaVonne and I had never been inside a SIP house until last July when, on a rare drizzly day, we visited Phillip and Heather at their new home. As Phillip reminded us, we were the ones who, many years ago, had taught him and Heather the meaning of the term "off-the-grid," and it seemed only right to see firsthand how well they had embraced it.

We needn't have worried.

Rex Ewing and Phillip Steyn next to the solar arrays.

After navigating through a branching network of winding dirt back roads where the quality of building construction seemed to diminish with every structure we passed, we at last arrived at the Steyns' 40 wooded acres at 8,500 feet of altitude. We drove past the barn and the pasture where horses and sheep grazed under the watchful eye of an Akbash—a large breed of dog, as distinguished for its ability to protect the sheep herd from coyotes and mountain lions as it is for its aversion to human contact—and pulled closer to the 2,700-square-foot, three-level SIP house where stone, stucco and logs had been blended into a proud and stylish edifice four miles from the nearest power line.

The couple's reliance on renewable energy was everywhere evident. To the west of the house a pair of pole-mounted photovoltaic solar arrays—each comprising eight Sanyo 170-watt multi-crystalline modules—stood as stalwart sentries in a clearing on the hillside. Phillip explained that each array was wired to its own OutBack MX60 charge controller, since the two arrays were shaded at different times of the morning and afternoon. It only made sense to wire them separately, otherwise the shaded array would draw down the power output of the unshaded one.

One of the Steyns’ propane fireplaces.

A good distance above the solar arrays stood a 50-foot fold-over pipe tower with a Whisper 100 wind turbine mounted on top, waiting for a wind not likely to happen under the current weather conditions. It too was wired to its own charge controller.

In the battery room in the basement, this considerable solar and wind potential is fed at 48 volts DC into a 3,800-pound bank of 12 Rolls 5000-series 4-volt batteries, which in turn supplies a pair of OutBack 3,600-watt inverters. These are wired in series to produce, in addition to normal 120-volt house current, the 240-volts AC needed to run the 11-amp, 1.5 horsepower well pump. To equalize the batteries and make up any power deficit that might result from a prolonged spell of bad weather, a 12-kilowatt propane-fired generator in its own outside enclosure is poised to start the moment it receives instructions—either from the inverters after a low-battery-voltage threshold is reached, or from Phillip, who can do it from the comfort of his upstairs office with an OutBack Mate remote controller.

This is all the kind of stuff that makes off-gridders drool, and the tour had just begun. Across the hall from the battery room, Phillip showed us the home's heating and hot water systems. Most conspicuous was the 470-gallon insulated tank holding water heated by the 12 roof-mounted flat-plate solar collectors (eight facing south, with four more on the garage facing southwest). A pressurized glycol-water mixture cycling between the panels and a heat exchanger keeps the water in the tank between 80°F and 170°F. The heat stored in this water is destined to either preheat domestic water en route to the on-demand propane water heater, or to heat the water coursing through a serpentine network of PEX tubing that runs under both the basement and first-level floors and the hot tub located on the wraparound deck. As a built-in safety feature, a radiator-style heat dump located under the deck dissipates extra heat whenever the water in the tank exceeds 170°F. And to make sure no heat is wasted—particularly heat created in the propane-fired boiler—the heating system receives its instructions from a Tekmar computerized controller that factors the outside air temperature's rate of change into the instructions it sends to the boiler.

The interior of the home stays cozy with R-16 SIP walls, R-48 roof, and large south-facing energy efficient windows.

Passive systems for heat and light begin with the large energy-efficient south-facing windows, which provide an abundance of solar heat that is greedily absorbed by the tile floors. For several hours after sunset, the heat is radiated back into the house. Considerable natural lighting from the south windows is available to the walkout basement, the main-floor kitchen and dining areas, and the reading room in the loft. Seven natural-light tubes illuminate the upstairs bathroom and bedrooms even on cloudy days. For nighttime lighting, compact fluorescent bulbs inhabit every light socket in the house—even the ones in the fridge.

The home's wiring is also cleverly innovative. Everything that can draw a ghost load is on a hard-wired kill switch. This includes the washer/dryer, dishwasher, microwave, tvs, VCRs and DVD players, computers, GFCI ground-fault protectors, and the garage door openers—things that collectively can put a considerable strain on the measured energy reserves of an off-grid home.

Solar hot water collectors on the roof.

Since Heather is allergic to wood smoke, there are four propane fireplaces throughout the house, all with an AFUE (Annual Fuel Utilization Efficiency) rating. They are so efficient, in fact, that their heat-producing potential was factored into the home's heating calculations.

It was everywhere evident that the Steyns were committed to using every watt and Btu logically and efficiently. As trained diagnosticians—Phillip is a certified radiologist and owner of eVetRads.com, while Heather is a small-animal practitioner and medical director of the VCA Fort Collins Animal Hospital—they are both accustomed to approaching every problem with methodical reasoning and keen attention to detail.

How well have they done? Well, if you've been practicing a bit of rough mental math, you have no doubt concluded that Phillip and Heather's house is remarkable, considering that all of their electricity comes from a 2,800-watt solar array and a wind turbine that tops out at 900 watts in the rare perfect wind. You may even have considered that a fair allotment of power must be diverted to run zone pumps for the home's hydronic heating system at the time of year when solar-energy production is at its lowest. The colder the house, the more electricity it takes to circulate the solar- and propane-heated water that warms it.

Structural Insulated Panels (SIP) were used in the construction of the walls and roof, which gives the home a much higher R-value than regular stick-built homes.

The energy components.

By the time we left Phillip and Heather's home, we were amazed at how well they lived on so little energy. Theirs is a house that could easily consume 30 to 40 kilowatt hours of electricity every day, and yet the Steyns live sumptuously on a fraction of that by conserving energy and making wise choices at every step along the way, from building materials and design features, to the choice of appliances.

At one point during the tour, Phillip wryly pointed out that "Sustainability does not mean subsistence." It seems he and Heather have driven that point home with a conspicuous flair.