* Steel-reinforced concrete to protect against tornadoes
* Meant as "living laboratory" for conservation, disasters
* Building materials alone to cost $6.9 million
By Kevin Murphy
KANSAS CITY, Mo, July 24 (Reuters Life!) - Now, here's a second home to stretch out in.
A Virginia man is building a 72,000-square-foot (6,690-sq-metre) house in the Missouri Ozarks with 13 bedrooms, 14 bathrooms and other features that could include a library, music room and theater.
With a footprint equivalent to a little under two acres (0.9 hectare) it would be one of the country's largest privately owned houses, according to various lists. The garage alone measures 4,000 sq feet (370 sq m).
But it's the materials that homeowner Steven Huff seems most proud of when he talks about the castle-like structure on 500 wooded acres (202 ha) in southwest Missouri.
The house is made from a special steel-reinforced concrete that is energy-efficient and resistant to various forces of nature -- notably tornadoes in an area prone to them.
Huff, 60, is chairman of TF Concrete Forming Systems, which makes the concrete. He grew up in Missouri.
His mansion-in-the-making, called Pensmore, has drawn so much attention and speculation that he released a prepared statement this week about it.
"The mission behind Pensmore is to serve as a living laboratory for ongoing research into energy conservation and disaster resistance," he said.
"While the structure will also be a home to my family, our hope is that curiosity and gossip will fade to make room for the valuable insights a project of this scale can yield for building the homes, schools, hospitals and office buildings of the future."
The idea is for the structure to be big enough to serve as a model of efficiency and durability for large commercial buildings, even though it is a house, said Luke Pinkerton, founder of Helix, which is providing steel for the project.
The concrete is mixed with bits of steel, poured into wall forms and insulated on the outside, Pinkerton said, and concrete absorbs the heat, keeping the house cooler.
There are already many buildings using the material, but Pensmore will be a high-profile example, he said.
"The concept is very relevant in our times," Pinkerton said. "Energy costs are getting higher."
Part of the house can be seen by motorists on U.S. Highway 65 between Springfield and Branson, Missouri.
The house is probably more than a year from completion, said Todd Wiesehan, planning and zoning administrator for Christian County. It will use nearly $6.9 million in building materials, according to the permit application, he said.
Huff plans to give tours of the house to the media and others in mid-August, said Eva Van Brunt, his spokeswoman.
Huff and his family will live in the house for part of the year, Van Brunt said. He has four children, Van Brunt said. (Editing by Tim Gaynor, Ellen Wulfhorst and Eric Walsh)