Fairbanks engineer focused on energy efficiency brings his work home

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Bruno Grunau's "net-zero" home in Fairbanks on September 9, 2015. Grunau, a research engineer at the Cold Climate Housing Research Center in Fairbanks, designed his home to be extremely energy-efficient and incorporated renewable-energy systems into the design so that the building produces nearly all the energy needed to heat it.

FAIRBANKS -- Two years ago, an engineer in the Interior Alaska city known for its unforgiving climate built a house that is kept toasty without fossil fuels and uses a mere fraction of the energy typically needed, even at 30 below.

Bruno and Judith Grunau's house sits on one of Fairbanks' rolling hills that span out from the vast Tanana Valley. On a clear September afternoon, autumn had painted the hillsides a vibrant yellow as Bruno Grunau toured his home.

Grunau is a research and testing engineer with the Cold Climate Housing Research Center, an organization which focuses on developing sustainable energy technology in sub-Arctic and Arctic climates. Judith Grunau is an architect.

"Our vision was to have a super energy-efficient home. That was an unspoken understanding between us," Grunau wrote later.

The home is considered "net-zero ready." That means if the couple were to add solar panels to offset the monthly electric costs, they would be completely off the energy grid.

The house is also, in a way, a testing ground. Since it's "one of only a few in this area, we can learn a lot from the system," Grunau said. And like many experiments, Grunau later said he'd do some things differently if he had the chance.

Grunau makes one concession: Elevated from the valley's temperature inversion, the house has never been hit with Fairbanks' infamous minus-40-degree cold snaps. "To be fair, I'm cheating a little bit," Grunau said. The coldest temperature the house has faced is 30 below.

Insulating 'to the extreme'

Turning down the steep dirt driveway, the house's first noticeable feature is its charred siding, a Japanese technique called Shou Sugi Ban. An eighth-inch of char on the outer wood protects the house from rot, insects and fire, Grunau said.

The blackened siding looks modern and chic. But neither the look nor the benefits spurred Grunau to choose Shou Sugi Ban -- he just didn't want to maintain painted siding on the house.

As Grunau toured his home, a theme quickly emerged: Warm and tightly-insulated building envelopes are the key to reduced fuel use.

"So, we did that to the extreme," Grunau said. The 2-foot thick Arctic Walls were specially designed, alongside a super-insulated roof and flooring. The windows are triple-paned, insulated with argon gas.

The result? Even without alternative heating systems, Grunau's 1,450-square-foot home would require about 200 gallons of fuel oil annually. That's roughly 87 percent less energy than the average home of the same size in Fairbanks, based on figures from a 2014 housing assessment.

The takeaway, Grunau said, is that insulation is key to efficiency.

The need is also clear: The average home in Fairbanks spends $8,106 annually on energy. The average Anchorage home spends only $2,786, according to the assessment.

Of course, there is a flip side of having a home so tightly insulated. The more efficient a home, the more important ventilation becomes, Grunau said. Grunau's house uses an HRV (heat recovery) system. Grunau believes it's best to think of a house as a holistic system, not just a collection of disparate heating, ventilation, and water systems.

A good example of this is his stovetop. He uses an induction stove, which looks like an electric stove, but with a major difference. The burner never heats up -- instead, a magnet excites the iron atoms in the pot itself, heating only the metal.

By using an induction stove, Grunau doesn't have to worry about carbon monoxide releasing into his highly airtight home by using a traditional heating element.

Energy systems and 'gremlins'

Two energy systems work in tandem to heat the house. Along the main facade of south-facing windows, six solar thermal panels collect solar energy. The heat is then stored in a 2,500-gallon underground tank, and the hot water runs through coils beneath the floor, which provides radiant floor heating. Separately, water used for bathing is run through the underground tank in coils and heated.

During the summer and autumn months, heat is stored up from the solar thermal energy. Once December rolls around, that stored heat is mostly depleted. That's when the second system kicks in -- a masonry heater.

The boxy heater is an $8,500 investment, but is also far more efficient than a standard wood stove. The masonry heater heats both the home and the water tank.

The trick is a system of coils within the stove. Wood burns fast and hot and then radiates out into the home for far longer than a typical stove (last year Grunau used less than a cord of wood). Grunau has also rigged a coil inside the heater that pumps water through and into the underground water tank.

To increase efficiency, the water in the underground tank is stratified -- the hot water is on top, and cooler water on the bottom. That means only several hundred gallons of water needs to be heated during the winter, not the entire tank.

There have been hiccups to the system -- the solar thermal system only worked at half capacity this summer due to a technical problem that Grunau has since ironed out.

Such technical issues -- what Grunau calls "gremlins" -- is one of the reasons he says a home built like his isn't for everyone.

Most people "want to set a thermostat and walk away," he said. With water pumps to worry about, and a masonry heater to stock when temperatures dip low, more effort is required than a typical home heated by fuel oil.

Secondly, there's resale. "If you're going to have a system like this, you've got to understand what it is. So it's going to be a challenge for me to sell this house," Grunau said.

These systems were also more costly than investing in a typical home, and there aren't good banking systems in place to provide for loans for emerging technologies. "We had to be able to have that money up front to be able to afford this," Grunau said.

Tips to reduce fuel usage

To improve upon an existing house's energy efficiency, Grunau returned to the common theme: Create a warm building envelope.

Replacing windows and adding insulation is easier and cheaper than investing in new technologies, he said.

He recommended applying for energy rebate programs through the Alaska Housing Finance Corporation -- both for existing and new homes, as well as weatherization programs for lower-income homes.

"That's a big step, because it's money up front," Grunau said. He also recommends improving any heat-delivery systems, such as installing a high-efficiency boilers.

But if a person is intent on arriving at a net-zero home, it probably will take new construction to get there.

"You need to start at the drawing board," Grunau said.

Still, Grunau says that for many people, improving an existing home makes the most sense. "There are huge steps you can take that are already in place," he said.