On a former soybean field in the rolling hills of northern Kansas, a few miles outside Lawrence, David and Susan Millstein’s contribution to environmental sustainability curves and bends around the Kansas landscape like an undulating gray ribbon. It’s an earthship. To be more precise, it’s a variation on the theme of this green building technology, which incorporates into its design thermal walls built of used automobile tires filled with earth from the site and passive solar heating.
Ten years’ worth of lovingly collected recycled building materials are incorporated into the modified earthship’s construction. Its windows are framed with cypress rescued from a mushroom barn; recycled flooring from a University of Kansas handball court covers the dining/activity room floor. The living room floor is fashioned of planks from old tobacco sheds in Louisiana, and the marble floor in the home’s entry hall comes from a hospital in Kansas City. The opening portholes that add a touch of whimsy to the second story are Navy surplus. All the interior walls get their color from tinted plaster, not paint.
Safe and sound
The house, which covers 2,700 square feet—3,000 square feet with the sunroom—is light and airy yet massive and secure at the same time. The first floor contains the living room, greenhouse, bedrooms for three children who are now grown (although daughter Casey, age nineteen, still lives at home while attending University of Kansas), and the dining activity room—which the Millsteins call “The Egg” because of its shape. The second floor contains the master suite and reading nook. And besides fulfilling the Millsteins’ desire to tread lightly on the earth, it’s exactly what they were looking for to insulate themselves from the endless Kansas prairie winds.
“We wanted this house to be passive solar and to use recycled materials, but we also wanted to let the wind play with this house rather than fight it,” explains David, who has a background in building restoration. According to Susan, the house has achieved their objectives and more. “There’s wonderful lighting that accompanies passive solar heating,” she says. “I love the light, and I wanted to use all these wonderful materials David had accumulated over the years.”
The house has cut their energy bills drastically. David says they spend about half what they paid for propane at the family’s former residence, a Victorian farmhouse. It’s also wired to accept direct current (DC) if the Millsteins ever go completely off the energy grid. “Being off the grid would be perfection, but the payback is so extended we thought conservation would be more pragmatic,” David says.
Inspiration for the Millsteins’ modified earthship came in the early 1990s. They had already done what they could with their traditional, turn-of-the-century farmhouse in terms of environmental retrofitting. “We added a greenhouse and some solar collectors, but the house was pretty inefficient,” David explains.
About that time they read about a free-form home made from lightweight Ferro cement, which is used more often in boat building than in home building. “That piqued my curiosity,” David says, because Ferro accommodates curves more readily than conventional, reinforced concrete. “My favorite architecture is definitely not square.” Soon after, a friend showed them an article describing actor and environmentalist Dennis Weaver’s so-called “tire house” earthship in Ridgway, Colorado.
From those two sources came David’s idea to combine the technologies and create his family’s personal Kansas-style earthship. “The vision sort of evolved,” he admits. “I doodled around with a number of ridiculous designs, but things started coming together when we saw the free-form Ferro cement house.”
As with all things creative, there were hurdles to jump, so the Millsteins decided to begin their construction with an outbuilding. “We learned a lot through that process,” David says. Specifically, they discovered that traditional earthship construction wouldn’t work in Kansas. True earthship tire-wall technology, developed in Taos, New Mexico, depends on dry soil and climate to work best. In eastern Kansas, where it rains about thirty-five inches a year, modifications to conventional tire-wall construction techniques had to be made. Instead of berming the tire wall, it was built as a freestanding wall, making moisture-proofing easier.
Construction techniques were also changed. “By the time we were working on the upper layers of the wall, it was like standing on Jell-O,” David says. “We were always having problems keeping things plumb.” The solution was to chink the tire layers with concrete at the end of each day so that when work on the tire wall began the following day, it was rigid enough to stand on. The tires on the upper level of the wall were pounded on the ground, set in place, then keyed into position with some finish tamping.
The Millsteins also found they couldn’t include the graywater systems often incorporated into classic earthship designs (see “Anatomy of an Earthship,” page 56) because of county building codes.
By the time the outbuilding was complete, the Millsteins had a pretty good idea of what they could and couldn’t do to replicate an earthship design in Kansas. They also managed to get county code inspectors to believe in the project. “For about the first eight months, they were skeptical,” David says. “They wanted some engineering done to satisfy their curiosity.” The couple asked John Easley, professor emeritus in engineering at the University of Kansas, to prove the home’s structural integrity. “By the time the process was two-thirds through, the county inspector had developed some faith,” he continues. “Then he got on board and was really enthusiastic.”
Tires and cement
The main house took about two years to build—most of the tire-pounding labor coming from David, friend Chris Robinson, and members of their son Josh’s high school cross-country running team. Its design incorporates only one freestanding tire wall, on the north side, which isn’t susceptible to the Kansas moisture. The wall contains 586 tires, while the outbuilding contains another 614 tires for a total of 1,200. Each was hand picked and cost nothing, if you don’t add in the cost of the labor to find them and fill each with 350 pounds of Kansas clay. “We had a route from Lawrence to Ottawa to Topeka to Kansas City. We sorted through piles of tires,” David recalls.
The endeavor may sound daunting, but the tire wall is crucial to the interior temperature of an earthship house. “The wall acts as a temperature-moderating influence,” David says. “The rooms that have the highest ratio of tire-wall area to room area are the easiest to heat and cool.”
The rest of the house was built using stick construction and Ferro cement. The Ferro cement allows for the home’s graceful curves and also made it possible to build a waterproof roof without having to use the water-repelling membrane typically required to keep water from leaking into a relatively flat-roofed structure.
In winter, however, the roof has a minor drawback. Ferro cement is semi-permeable, which means while water won’t pass through it, vapors do. “In continuous below freezing weather—which we don’t get much of—vapor freezes on the underside of the Ferro, and we get a little condensation, which watermarks the ceiling in the high areas where the vapors collect,” he says. If he were to do it over again, David would put vents in the roof’s highest sections to allow vapors to move more freely. Susan adds that because sound resonates so well off the plaster walls, she might have opted for some softer surfaces.
When it was completed in 1995, the Millsteins’ earthship cost between $60 and $65 per square foot. That’s about half of what traditional home construction cost at the time. But, David is quick to note, “that’s not including my labor.”
All in all, however, the Millsteins declare their modified earthship a resounding success. “I feel good about the house. It’s holding up great,” David says. “It provides us with a really nice environment.”