Sunday, March 22, 2009
Rammed-earth construction is solid and efficient
By Story By Kathryn Holzka
For the Journal
Energy-efficient, sustainable building is hardly new.
In fact, a technique called rammed earth goes back thousands of years and is undergoing a resurgence as residential construction becomes increasingly greener.
Darrel and Julia Mummert, for example, decided to raze the old house at 330 Vineyard NW in Albuquerque in favor of building a rammed-earth home designed in the style of northern New Mexico farmhouses.
The new 2,368-square-foot residence was designed by Santa Fe architect David Perrigo, built by David Langham of Home Construction and Consulting Services, and dreamed up by Darrel Mummert, who has been "fascinated with adobe and earth construction techniques since the early 1990s."
Julia said she was less an aficionado of such down-to-earth building materials, and, as a Texas-born, Louisiana-raised Southern gal, was more into the antebellum homes of the South.
But she got caught up in the idea after listening to her husband's sale's pitch over the last few years, reading up on rammed-earth homes, and visiting several in Edgewood and surrounding areas. Before long, she said, she found herself sitting around the kitchen table discussing ideas and helping draw up plans with the designer and her husband.
"It was either put up with the defects of the old adobe house we bought four years ago, completely remodel it, or tear it down and build a new home on the site. We bought the house originally because of the beautiful property it was on, but when we got the estimate on a complete remodel, we decided it was more cost-effective to demolish the old house and build a new one," she said.
The rammed-earth walls for the house were built by Chandler Huston of Edgewood, of a third generation of rammed-earth builders who helped pioneer the technique in Central New Mexico.
It was Stan Huston, Chandler's father, whom Darrel Mummert met some 15 years ago at a Southwest Solar Adobe School he was attending to learn earth-build techniques, and who introduced him to the rammed-earth construction method. Huston was demonstrating the method at the school.
"Rammed-earth building goes back thousands of years and was used to build the Great Wall of China," Chandler Huston said, adding that there are many examples of rammed-earth buildings in Europe and in the United States.
"It takes longer to build, but when you're done, you don't have to spend time or money on paint, plaster, insulation or stuccoing," he said.
Langham said the exterior wall construction of the Mummert house took about 10 weeks to complete. The walls are 24 inches thick and built in sections 8 feet high by 8 feet wide.
The earth is stabilized with cement in a ratio of 80 pounds of cement to 1,000 pounds of soil and mixed with a small amount of water on site with a special machine. It is then funneled to the wooden forms by metal chutes similar to those used in pouring cement from as cement mixer, then pounded into a solid shape by a pneumatic rammer to produce the finished wall panel.
"Rammed-earth walls have a compression strength of 300 psi and achieve their maximum hardness in two years," Langham said. "The walls are so thick and hard they are actually bulletproof, and you can drill into them and anchor into them, unlike adobe, which will crumble."
The home is 40 feet by 70 feet, with a 16-foot-center pitched roof. At the core of the house is a large open kitchen/dining/living area, off of which are separate wings for the children's room on one end and the master bedroom/bath, guest room and office on the other end.
The house has three bedrooms, a home office and 2 1/2 baths. The bedrooms have high windows to catch the sun and two external roof dormer windows that help admit light and sun to the interior of the residence. The building is positioned lengthways down the narrow part of the lot to take maximum advantage of the mature trees and existing landscaping, leaving a huge backyard for the children to play in.
The home's vaulted ceilings are finished with structural tongue-and-groove pine, and the rustic look is complemented by the use of exposed decorative wooden trusses.
Both Langham and Mummert said the home is extremely energy-efficient because of the thermal mass of the rammed earth and the use of materials that absorb and store energy, including the concrete floor, which enhances heat absorption throughout the house.
The home also uses energy-saving compact fluorescent lighting, vapor-type barn track lights along the trusses, and Energy Star-rated appliances.
"The solar orientation, reflective galvanized roof, double-pane wood and aluminum windows, hot water recirculation with timer, deep front and rear porches and eaves that are two feet deep all add to the home's energy efficiency," Langham said.
Mummert said the home also incorporates low-flow toilets, gutters, downspouts and rain catchment barrels.
"There is excellent natural air circulation and ventilation, and the home will require minimal usage of artificial heating and cooling methods due to the type of construction and thermal mass," Mummert said.
He said the old home that was demolished was recycled and some elements were incorporated into the new home built in its place.
The home has been selected to be part of the 10th annual Green Built Tour, scheduled for May 16-17, sponsored by the New Mexico Chapter of the U.S. Green Building Council.
Langham said that through careful planning and use of rammed-earth technology, the Mummert residence came in at $137 a square foot, including all taxes and construction fees, "and that's about on a par with many tract-built homes, except you are getting a custom-built home that is uniquely yours."
Mummert said the project cost $325,000 and that the appraised value, including the land, is $550,000. The demolition of the old adobe house on the site cost $10,000, he said.
"If you like to build unique homes, the more unique they are the more fun they are," Langham said of the Mummert project. "A lot of builders don't like to get away from the traditional methods of construction. But I love a challenge and have built in practically every method of construction, from frame to rastra, insulated concrete forms, adobe, rammed earth and structural insulated panels. It's the challenge of unique designs and techniques that make the job fun."
Additional photos and information on the rammed-earth home are available at Langham's Web site, www.abqbuilder.com. Click on "Portfolio" and then on the link to the rammed-earth house.