|
Prefab Concrete Panels Enhance Green Dream Home
Dovetailing with a surge in consumer interest in green building and energy-saving technologies, a 9,200-square-foot dream house built by two airline pilots on a stunning site in Prairie Grove, Ill. illustrates how prefabrication is becoming an increasingly popular and effective choice for boosting the performance of residential structures.
In her new book, “Prefabulous — the House of Your Dreams Delivered Fresh From the Factory,” author Sheri Koones, describes how Steve and Jackie Smith's home used a concrete system called Solarcrete to provide a sustainable method of construction that at the same time allowed for modern interior design with a strong connection to the outdoors.
Unlike in Europe, where concrete homes have been built for hundreds of years, concrete was rarely used for residential construction in this country until only recently, says Koones, although it has made significant advances over the last decade.
In 1993, approximately 3% of the homes built in the U.S. used prefab concrete panels, she says. Today, about 16% of the nation’s homes are being built using some type of prefab concrete system.
“Although concrete has typically been a more costly method of building,” writes Koones, “its popularity is growing because it is plentiful, easy to create in a variety of colors and in a multitude of forms, is virtually weatherproof and bugproof, and when reinforced with steel is strong enough to stand up to hurricanes, tornadoes and earthquakes.”
She adds that concrete can also be a highly energy-efficient material for home construction because of the material’s thermal mass and airtight qualities.
The prefabricated panels used in the Smith House consist of about 7 inches of expanded polystyrene insulation sandwiched between two parallel sheets of wire mesh or reinforcing bars and held together with ties. The pre-engineered panels are then transported to the site and attached to the foundation with steel dowels that have been precast into the foundation.
“Spaces are cut out for the windows, doors and plumbing, and wires are snaked through the foam insulation before the panels are coated with about 3 inches of concrete sprayed onto each side,” says Koones. “After the concrete is applied, the surface is troweled to a smooth finish.”
The roughly 12-inch wall created in the process provides an excellent insulating envelope and thermal mass to even out temperature fluctuations.
The architects and home owners had to be diligent about planning to ensure that adequate electrical conduits and outlet boxes were installed before the panels were constructed, and more than required was used to meet future needs.
Because the house was being built to withstand the elements for at least 100 years, “we wanted to make sure that it could meet the needs of other families many years from now,” said Jackie Smith.
The house was oriented on its lot to take advantage of the sun while minimizing east and west exposures. A long southern exposure collects more solar heat, and a garage and service area requiring less heat are located on the north side of the house. Sun shades extending over the upper windows were angled so that in the summer when the sun is high, windows are shaded, while in the winter when the sun is low, sun floods the rooms and provides extra warmth.
Unlike most radiant floor systems, which only provide heat, the home’s Airfloor system is also used for cooling. A series of hollow, interlocking metal channels are placed on the subfloor and covered with concrete. When the system is activated, air is forced through the network of forms, creating a radiant floor and ventilating system. In the Smith House, the heated or cooled air from a geothermal heating system is pumped into the floor.
The system is supplemented by electric heat.
Koone’s book provides other examples, similar to the Smith House, of the most commonly used building systems, which, in addition to concrete, are modular, panelized, log, timber frame and steel frame.
In general, she says, prefab building methods are conducive to making homes stronger, reducing construction waste, boosting energy efficiency and reducing material and labor resources — all objectives of the green building movement.
While the prefab home industry focused on low-cost small houses rather than great design when it found its footing in the 1950s, she says, in the last decade or two “architects, builders and home owners have begun to take advantage of what is called, in the industry, systems-built homes. Along the way, good design has crept back into the process.”
Koone cites the Portland Cement Association's Web site (cement.org) as a rich source of information on concrete, its uses and its properties.
“Prefabulous” is available at local book stores, chains and Amazon.com.
For more information on building systems resources available from NAHB or the NAHB Building Systems Councils, e-mail Cortney Klein at NAHB, or call her at 800-368-5242 x8357.
Photos courtesy Farr Associates
 Attend the BSC Modular and Panel Plant Tour
Attend the 2007 Building Systems Councils Modular and Panel Plant Tour from May 20 to May 22 in Roanoke, Va.
The tour will provide interested builders the chance to go behind the scenes of the fastest growing segment of the residential construction industry with visits to up to four manufacturing facilities in just two days.
Builders on the tour will see the quality and efficiency of modular and panelized homes and have the chance to meet and network with building systems professionals from across the country.
For more information or to register, click here.
|
