An Idaho woman's home addition includes a "living floor" with various plants.

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When she added on to her home, Jeri Rutherford found a way to go green — literally.

A 170-square-foot dining-room addition has helped cut her power bills by as much as 20 percent. And it brought a lush, if small, island of tropical greenery to her home overlooking the Snake River near Marsing.

“I love the tropics and the fern grottos of the California redwood forest,” she said. “I know I can’t be there all the time, so I wondered how I could bring those places into my home.”

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The result is a living floor and wall with plants that clean the air and — paired with a whole-house fan and a heat well that releases hot air through a skylight — help cool the entire house.

“I have square feet of natural refrigeration,” Rutherford says, thanks to the plants’ ability to transpire and evaporate water in addition to clearing the air of pollutants.

Meanwhile, the fan helps change air in the house every 13 minutes, reducing the need for air conditioning. And in winter, the plants and soil act as an insulator and moderator of temperature.

But the best part, she says with a straight face, is her morning coffee.

“I like to sit with my shoes off and drink my coffee with my feet on the moss of the living floor,” she said. “When we have inversions and it’s nothing but gray outside, that’s where I’ll be. In my fern grotto with my feet in the moss.”

Sound appealing in Western Washington, land of the green, home of the green thumbs?

Prepare to work at it, said Joe Abken, manager of Sky Nursery in Shoreline. Area homeowners hoping to try something similar would face several challenges, including structure and lighting, not to mention the potential costs. “It’s an ambitious project,” Abken says.

It would first require a built-in planter or, for example, a rot-resistant pond liner to separate the soil from the home’s wood foundations, plus a plumbing system to drain excess water. “Moisture’s a big problem inside of a house,” he says.

Even with an atrium or multiple skylights, Seattle’s rainy climate would limit the plants one could grow, since a typical lawn requires six hours of sunlight. “Shady lawns here are thin and mossy at best,” he says.

Trailing plants, low-light plants and some herbs would be possible, but probably not many edibles, he says.

“It’s certainly an intriguing idea,” he says, but the expense could be substantial, especially if retrofitting an existing home. “You want to make sure whoever’s doing it knows what they’re doing. You don’t want this to come back at you in a resale situation.”

Idaho Power gave Rutherford a $450 incentive for incorporating energy efficiency and conservation into a new living space. It was a small fraction of the $17,000 cost of the project. But Idaho Power Energy Efficiency Engineer Chris Pollow, who worked with Rutherford on the project, says it could serve as an inspiration for other customers, considering the potential energy savings.

“What impressed me is that she added square footage and electrical load with the pump for the plants’ irrigation system and still cut energy costs,” he said.

Rutherford’s power bill was down 20 percent from the previous year for the first month she was using the addition. The savings the second month were 5 percent.

The difference, she said, was that she was traveling the second month and not home to open downstairs windows or turn on the fan to ventilate the house. Average savings are expected to be about 10 percent.

But it’s not just about savings. Rutherford says the plants almost double the humidity in her home, providing relief from sinus problems and dry skin. A friend jokes that she’s saved $50 a month on moisturizing lotions.

“And the house smells lovely,” she said. “It’s like being outside when you’re inside.” The 4- by 12-foot living wall has 350 plants growing from a layer of Miracle-Gro. Blossoming plants in the wall and ground cover on the floor (rooted in soil supported by a fiberglass bowl resembling a mini-swimming pool) provide what she calls “an ever changing palette of color.” Some of the plants — basil, strawberries, chives, oxalis — are edible.

Bugs? No problem. Extending the green approach to pest control, Rutherford now has a live-in gecko and praying mantis. Seattle’s Abken notes that the idea of bugs in the home “may not be doable for some people.”

Seattle Times staff reporter Marc Ramirez contributed to this feature.

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