Arizona's green adobe home
Desert colors are still popular in the Southwest and other areas of the country, but so is green — the shade of green that equates with eco-friendly products, such as the adobe bricks used in the construction of a home in North Scottsdale, Ariz. Built by Greg Hartman of FHP Builders, a Scottsdale-based developer, the 4,400-square-foot custom residence, built on a cul-de-sac, is the only adobe home in a neighborhood of million-dollar residences.
Adobe makes a natural building material for an eco-friendly home, for a number of reasons. “Adobe is comparable to rammed earth and straw bale in its insulating mass,” Hartman says. Besides substantial thermal properties, adobe’s acoustical benefit keeps outside noises from intruding into the home.
Adobe is far more durable and sustainable than the wood framing and stucco Arizonans usually opt for when constructing their homes, and the sun-dried blocks, made of clay or dirt and straw, provide an aged, weathered appearance. In addition, Hartman compares adobe’s structural integrity to the brick and stone masonry used in the Midwest and Northeast.
Another green element is its embodied energy cost — the price tag associated with a product’s manufacture and transportation. Compared to concrete (made by crushing limestone and heating it at a high temperature in a kiln), adobe’s embodied energy cost is low. It does not require a kiln to cure — the sun does the work — and since it is available locally, transportation costs are low.
Building with adobe
A typical 2,500-square-foot home requires 13,000 to 15,000 adobe bricks. Hartman’s more spacious 4,000-plus-square-foot home required 28,000 bricks. Each adobe brick measures 12 by 4 inches and is 16 inches deep, resulting in thick exterior walls.
Adobe does not require the added expense and energy expenditure of paint or wall insulation, but it does offer those decorative exterior options. The final appearance can vary according to taste. Homeowners can coat it with mud gypsum, lime plasters or Portland cement stucco, then paint.
Since 70 percent of the exterior and interior walls in the Hartman house are constructed with natural adobe bricks (the remaining 30 percent of the home is wood frame construction), the home easily met Scottsdale’s advanced green building standard. “My [home] office’s interior walls are [wood] frame,” Hartman says. “This saved money on materials and doesn’t affect the home’s energy efficiency.”
A Pennsylvania native who studied architecture and business at the University of Arizona School of Architecture in Tucson, Hartman is sold on adobe as a building material, and recently investigated the manufacturing process. He took a three-day seminar to learn about its manufacture and subsequently bought the Old Pueblo Adobe Company, an adobe brick factory originally located in the town of Marana, near Tucson, and is now based in Buckeye, near Phoenix. The company turns out as many as 25,000 adobe bricks a week.
Although adobe is a natural, clay-based material, it takes some know-how to turn it into a durable building product. Adobe can be stabilized or unstabilized. To create stabilized bricks used for building, a 3 percent asphalt emulsion for waterproofing is added to the earth-water mixture. A machine then molds the mix into 50-pound bricks, which are left to bake in the sun for 15 to 20 days, depending on the season.
While adobe is ideal for hot, dry desert climates such as Arizona, where summer temperatures can easily exceed 110 degrees, Hartman says it also can be used in damper weather zones, such as on the East and West coasts. “In Seattle, for example, I would put a stucco treatment over it,” he says.
Whatever the locale, adobe has a high R-value (the 16-inch-thick solid walls provide heat storage for temperature stability). Although the bricks cost 10 to 20 percent more than lumber, adobe ages more gracefully and requires less maintenance than wood construction. And the resulting energy savings helps homeowners recoup their building costs in seven to 10 years.
In addition to adobe bricks, 75 percent of the materials Hartman used in his home are native to Arizona. Environmentalists laud this type of building, because buying local (within 500 miles of a project) decreases the depletion of other eco-resources, such as fuel for transportation. For example, Hartman purchased chocolate-hued flagstone from the Yavapai Indian Reservation in Sells, Ariz., for use on the windowsills and pool edges, and landscaping came from a local nursery.
The wood for interior accents came from a number of different sources. Lumber for the rough-sawn ceiling beams and roof came from recycled wood waste or sustainable sources certified by the Forest Stewardship Council (FSC). Domestic hardwoods, such as alder, were used for the solid doors and kitchen cabinets. Alder is an eminently green wood choice, since it is fast-growing and underutilized.
For the kitchen counters, Hartman opted for granite, and he laid travertine, concrete and engineered wood flooring in all but three rooms, which have wall-to-wall carpeting. Bare floors are cost-effective and help conserve energy, since they require less maintenance. Carpeting, by contrast, can trap mold and germs and emit toxic vapors.
The home’s cabinets and doors are formaldehyde-free, and the interior paints and stains Hartman used were non-toxic, low- or zero-VOC (volatile organic compound) products, which help ensure good indoor air quality. The same applied to adhesives for the wood flooring, tile and wall-to-wall carpeting and padding.
“I went from an 1,800-square-foot house to a 4,400-square-foot house, and my energy bills are the same,” Hartman says, comparing his former frame/stucco house to his new adobe brick residence. He says owners of adobe houses gain a 50 to 75 percent savings in their energy bills. The heavy insulation of the thick brick walls is one reason for the home’s energy savings, but there are others.
The home’s HVAC system, which neutralizes unpleasant odors, stuffiness and excess moisture in addition to cooling and heating the home, comes with a Seasonal Energy Efficiency Rating (SEER) of 17. (The LEED, or Leadership in Energy and Environmental Design, home rating system requires a SEER rating of 13 for green certification.) Also, the air supply and return ducts are installed 8 feet underground, which minimizes energy loss before the conditioned air reaches its intended space. In addition, Hartman says the house is well ventilated, so it uses less energy on cooler days.
Other energy-efficient features yield substantial energy savings, including natural daytime lighting plus built-in task lighting; programmable thermostats in five zones adjustable to different comfort levels; ceiling fans to maximize cooling; low-voltage lighting; and tubular skylights in closets.
The home’s reflective roof surface helps reduce heat buildup and lower air conditioning costs, and insulation made from recycled newspapers in the attic ceiling reduces heat entry. Energy Star-rated appliances (dishwasher, refrigerator, washer and dryer) and a drying rack help keep energy costs down. Hot water lines are insulated, and instead of heating 40 gallons of water 24/7, a tankless hot water heater responds instantly on an as-needed basis.
Hartman says if he had to build the home all over again, he would opt for a solar energy system to take advantage of Arizona’s year-round sunshine. He did, however, plan for the future by installing conduits on the roof for a solar hot water (thermal) system if he decides to add one.
In Arizona, water is a limited and precious resource. To conserve water, Hartman turned to a zoned irrigation system for landscaping. An irrigation controller with a rain sensor shuts off the irrigation when it is not needed. Also, Hartman employs gray-water and rainwater collection systems, complete with roof scuppers (drains) and a cistern. The gray-water system draws from recycled bathroom, dishwasher and washing machine water. Four low-flow toilets also reduce overall water usage.
Water conservation and the minimal use of materials and toxic chemicals extend to the pool and spa as well. Pool filtration uses a zero-water-loss backwash system that recycles filtered water back into the pool, eliminating any need for complete pool drainage. Taken together, these systems reduce water bills and overall consumption.
In addition, the low-chlorine pool filtration system eliminates harmful exposure to chlorine and protects the sensitive tissues of the eyes and skin, as well as the respiratory system. The drinking water is also healthier (and better tasting) thanks to a point-of-entry water purification system that removes lead, radon, nitrate and organic chemicals.
Hartman does not use chemical herbicides or pesticides on the landscape, and he employs a house filtration system that improves air quality through the elimination of toxic gases, molds, pollen and particulates. He even ensured healthy air quality in the detached garage. A timed exhaust fan, wired to the garage door, vents carbon monoxide fumes so they won’t enter the house. Should too much of the poisonous gas penetrate, a carbon monoxide detector warns of high levels.
More than 90 percent of the one-acre site features xeriscape landscaping with drought-resistant plants. Where possible, Hartman left the desert vegetation undisturbed, replanted much of the ground cover and flora around the home, and introduced new native vegetation to the site.
In addition, he positioned trees for optimum shade, and installed a gazebo to lower the outside temperature around the house. Recessed doors and windows serve the same purpose, reducing the amount of heat absorbed into the house. Hartman’s investment in energy-efficient, double-paned, aluminum-clad Marvin window packages allows natural daylight to enter and minimizes the need for artificial lighting.
For the circular driveway, Hartman used rain-permeable decomposed granite, which cuts down the amount of heat absorbed and re-radiated from the surface. Inside and out, this adobe home proves that new techniques can mix easily with time-tested building materials like adobe to create a uniquely green home.
Janice Arenofsky has written for Newsweek and The Christian Science Monitor, among other publications. She’s based in Scottsdale, Ariz. You can visit her online at www.janicearenofsky.com.