Built on a hilltop in a prestigious neighborhood overlooking Phoenix, Ariz., the Howell Residence is a masterpiece. The Southwest-style home features clean lines, an open floor plan and a functional layout.
According to Gary Fetters of Castle Rock Construction, who built the home, ICFs were a perfect choice. "With the extremely hot temperatures here in Arizona, and the house sitting on top of a hill with total exposure to the sun at all times, this house needed the insulating qualities
Building it proved to be a challenge, though. The design has 36 corners in the exterior walls, eight of them at 45 degrees. Long lintels, including an 18-foot span over the garage and a slightly shorter one in the back also required careful engineering. Additionally, the home used multiple core sizes: a four-inch core for interior walls and stairwell, eight-inch block for the retaining walls, and six-inch-core blocks for the home itself. Fetters says, "These homes you cannot afford to be off your game."
Knowing the neighborhood would have zero tolerance for foam dust migrating from the jobsite, crews used only hot knives to cut the blocks.
The biggest construction challenge, though, was the steep lot. The plans called for extensive retaining walls, originally to be built with removable forms, but the logistics of getting the heavy forms down the hill, set, poured, stripped, and then hauled back up the hill made the cost estimates soar. Fetters says, "It made much more sense to use a lightweight form that could stay in place, and we just happened to know of a product that would fit the bill." He estimates the decision to use the ICF for retaining wall, staircase and the pool saved $13,000.
Still, the excavation and retaining wall work was "tough, long and costly." He says, "We spent the first four months of the 12-month build time just getting up the hill." Part of the challenge was that the basement had to nest inside the retaining walls at a precise matching angle. The solution was to start at the bottom, building the lower retaining walls, then a little bit of the basement, compact the fill between them, then back to the retaining walls, and so on until they reached grade.
The steep slope also greatly limited site access and mobility. Fetters says, "We had to get the ICF pool in before the house, because once the house was started, there would be no way to access the back."
The infinity-edge pool also had to be aligned precisely. "All the retaining walls, the pool’s knife edge and house all had 45-degree angles that had to be perfectly parallel from the bottom of the first retaining wall to the top of the roof, which was almost 50 vertical feet," he says.
In total, the 2,900-sq.-ft. house used 7,000 sq. ft. of ICF, split about evenly between retaining walls and structure.
The strength of ICF not only holds the hillside in place, but also allowed the designer to fit the owner's long-dreamed-for recording studio under the garage. The reinforced concrete core of the ICF walls carry a decking system strong enough to support two large vehicles, and the foam panels dampen exterior sound.
During the three hottest months of the build, temperatures at the jobsite topped 110 degrees daily. Obviously, energy efficiency was a priority. To augment the ICF walls, designers included large porches, breezeways, and overhangs in the back for shade. The roof is capped with 12” of open-cell polyurethane foam.
During construction, the project served as a landmark. "The home is located in a very prestigious area of Fountain Hills about 100 feet from one of the busiest roads in Phoenix suburbs," says Fetters. "This build was seen by thousands and thousands of commuters every day. We have had more ICF leads generated by this one home than any other home we have built."
The new owners are also extremely happy with the home. They're reportedly saving 40% on energy cost and 10% on homeowners insurance. Noise from the busy boulevard is greatly mitigated by the ICF walls. Mike Howell reports his guitars in the studio benefit from the constant temperature and humidity levels. Linda Howell adds, “We love taking vacations and had a trip planned for Europe, but we love our ICF home so much, we just don’t want to leave."