Cool home: Scottsdale's first straw-bale house still offers inspiration
The straw-bale house, with the thick walls and the adobe exterior, is perfect for the Southwest
- Kevin Edwards grew interested during high school in designing homes that minimized reliance on oil
- Edwards and wife Stacy bought a lot with no municipal water, no sewer, and a dirt access road
- After attending a straw-bale workshop in Tucson, they built their home from the material
On January mornings, Kevin and Stacy Edwards savor the warm sunlight pouring into their cozy living room. In July, the same space stays cool and comfortable with barely an assist from the air conditioner. Not bad for a house made of straw.
Wait, straw?
Indeed.
The story starts during the 1970s oil embargo, when Kevin, then a student at Chaparral High School in Scottsdale, realized how much modern life required fossil fuels. Already interested in construction, he resolved to design buildings that minimized their reliance on oil.
He studied architecture and alternative energy at NAU, then moved to California to join his brother Doug in a sustainable design-build firm, Edwards Design Group.
Planning their own home
By the 1990s, Kevin and Stacy had returned to Arizona with their two children. But living in a conventional house didn't suit Kevin, who also co-hosted Scottsdale's Green Building lecture series and spent his work days educating clients and peers about high-efficiency design.
Instead, the couple decided to build a new house that would be as sustainable as possible, using minimal energy that would be supplied by solar power, and made from recycled materials that would otherwise be wasted. The project would also allow Kevin to experiment with ideas that were at the edge of construction norms.
So, in 1997, they purchased a lot in far north Scottsdale. It had no municipal water, no sewer, and a dirt access road. It was perfect.
Sustainability through design
Knowing that the majority of home energy use goes to heating and cooling, Kevin needed to design a house that would maintain a comfortable temperature with little help.
To that end, he said, "the number one best thing you can do when building or buying a house is to consider the orientation and how it relates to the sun's path."
Since the harsh summer sun comes from the north and the more welcome winter sun from the south, Kevin aligned the house on an east-west axis, with large windows on the south side plus a few on the north for ventilation, and none on the east or west. For extra insulation from direct morning and afternoon light, he added an earth berm against the east wall, while a carport shades the west.
Kevin also wanted the house to have thick walls and floors to create as much thermal mass as possible.
Thermal mass, he explained, is like a battery.
"It takes in heat during the day and releases it at night," he said. "So the house feels cooler in the summer and warmer in the winter."
A house made of straw
Seeking a way to create that battery effect with recycled materials, Kevin came across a book about straw-bale houses. He loved the idea immediately, with the thick walls and the adobe exterior — perfect for the Southwest.
Because they are so densely packed, straw bales have exceptionally high insulation values and are extremely flame-retardant.
"But also," he explained, "straw is what's left after wheat is harvested. It's waste."
Intrigued, Kevin and Stacy attended a straw-bale workshop in Tucson. They came home, he said, "totally jazzed to do this."
They bought 600 bales from a ranch in Goodyear — each a hefty 24-inches thick by 48-inches long — which they stacked like giant bricks within a post-and-beam frame. Kevin plastered the walls with cement, which he tinted with natural iron oxides, creating a warm color that doesn't need paint.
The floor is even thicker than the walls, extending down three feet to take advantage of geothermal regulation. But it isn't solid. Horizontal air chambers run beneath the polished concrete surface and are vented to help with air circulation.
The completed house measures 2,600 square feet inside, but the thick walls push the entire footprint over 3,000.
Old materials, new life
In addition to the straw, Kevin and Stacy recycled 16 windows from a school gymnasium, leftover tiles from a hotel project, and several wooden pallets that Kevin used to panel the ceiling in the master bedroom.
"The thing about using surplus materials is that you have to get creative," Kevin acknowledged, "but it saves money and you can end up with wonderful things you wouldn't otherwise afford."
Ideas from around the world
In addition to repurposing materials, Kevin borrowed many ideas for desert design, including the most dramatic feature of the house: a 30-foot cooling tower inspired by Middle Eastern architecture.
With four rectangular openings at the top, the tower looks like part of a mission church but functions like a swamp cooler, with air flowing past misters then dropping naturally to cool the home below. Doors at the base of the tower open into the living room and help regulate the cooling effect.
"It works really well," Kevin said. "There are a lot of traditional strategies like this, but in modern buildings we've tried to replace the natural physics with mechanical systems."
Power from the sun
But in addition to time-tested strategies for desert living, the family wanted modern conveniences, so they mounted a solar water heater and a small array of solar panels on the roof.
Those solar panels, however, wouldn't go far without good design choices, Kevin said.
"Solar is great, but it's expensive, so before you put it in, you want to do all the other things first, with orientation and a tight building envelope and high-efficiency appliances," he said.
Mainstream sustainability
The Edwards house, which was completed in 1999, was the first straw-bale house in Scottsdale and is still one of only a few dozen around the state. Due to both its Southwestern aesthetic and high-efficiency cred, it has been featured in Phoenix Home & Garden magazine, the television show "World's Greenest Homes," and several home tours.
But, although straw-bale construction hasn't yet caught on — even among Kevin's clients, he has been happy to see other sustainability strategies become commonplace.
"We've been able to move these ideas into the mainstream, so that something that used to be kind of out there is now pretty normal," he said. "I feel that I've been some little part of that and that gives me a lot of satisfaction."