AAC house
Photograph: Rick Olivier
This Mediterranean-style AAC house in Niceville, Florida, is finished with stucco applied directly to the wall, no lath required.
With a pop, Chris Poate lights a pro-pane torch and moves the flame close to what looks like a double-thick slice of white bread. "Watch this," says the north Florida builder, his voice revealing his Australian roots. He toasts one side of the stuff—called autoclaved aerated concrete (AAC)—until it's cherry red and then offers the other side to a visitor. The toast is cool. And it's light—about half the weight of concrete, which it was invented to replace. "That's just the beginning," Poate says with a grin. Some call Autoclaved Aerated Concrete (AAC) a near-perfect building material. Patented in 1924 by a Swedish architect, AAC is made of common ingredients: portland cement, lime, silica sand or fly ash, water and a dash of aluminum powder. The material is acoustically insulating, energy conserving, resistant to fire, decay and termites, and can be cut with a handsaw and sculpted into architectural details. Europeans have built a million houses and buildings with AAC, but attempts to introduce it here failed until recently, when energy concerns and high lumber prices started opening minds to its possibilities.

Plaid Bermudas flapping around his tanned legs, Poate jumps out of his van at a house that his firm, Advanced Coastal Construction, is building from AAC. It's 92 degrees Fahrenheit in the shade along Florida's Choctawhatchee Bay, but when Poate walks into the unfinished house, the temperature is much cooler, and the construction noise from upstairs hardly penetrates the 10-inch-thick steel-reinforced AAC floor panels. The panels were made by Hebel, a German manufacturer that, in 1996, opened the first AAC factory in this country. (Ytong, a competitor, opened an AAC plant here in 1997.) The home owner, Richard Grenamyer, has wanted an AAC house for a long time. "I read about it years ago, but it wasn't available," he says. "A friend had Hebel block shipped from Germany to build his house in Tallahassee. I was excited when I saw the Hebel signs." What slowed AAC's arrival in the United States was the reluctance of some masons to learn new work habits, says Bob Shuldes, a consulting engineer at the Portland Cement Association who has studied the material's history. But watch mason Mark Harrison at work, and it's hard to see why. "It's easy," he says, cutting a block to size on a big band saw and adding it to the waist-high wall at another house on Poate's tour. Harrison sets down his trowel to pick up one of the AAC blocks. At 24 inches long, it is larger than a typical concrete block and, at about 30 pounds, it is lighter—but because it is solid, Harrison has to use two hands. American masons are used to grabbing the web of a concrete block and hefting it into place with one hand. Harrison doesn't mind working two-handed, but some masons never get used to the difference.

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