This is the 72,000 Sq. Ft. Eco-Mansion Going Up in the Ozark Mountains -- But Why?

There's a 72,000 sq. ft., 13-bedroom, 14-bathroom, mansion going up in the middle of the Ozark Mountains. And as the walls take shape, so do the theories about what exactly it is. According to the New York Times, some say it's a military bunker, others say a low-profile getaway for local phenom Brad Pitt and Angelina Jolie. And still others speculate it's there to host aliens.

“It’s really strange, and we’re thinking something’s up,” Michele Grider, who lives just down the road from where the mansion is being built, told the Times. “If there was a nuclear thing they could hide a bunch of important people there.”

It's called Pensmore, and its location is the opposite of its architecture: inconspicuous. It's located halfway between Springfield and Branson, MO. And it's bigger than the White House.

The owner, 60-year-old Steven T. Huff, used to own a company that makes software for military and intelligence agencies, further fueling speculation about the complex's use. According to him, it's just a large second home.

But while speculation exists about the mansion's primary purpose, it's clear what it's secondary purpose is (if not really the first): to trumpet green technology.

"Energy efficiency and enduring sustainability are the twin missions of Pensmore," the complex's website says. "The values and beliefs behind these principles are firmly held: a belief in good stewardship to the earth and fellow man, a belief that oil, gas, and coal as energy resources will become increasingly expensive and thereby unsustainable, and a belief that one ought to leave a positive impact in the world."

"Sustainability means more than just energy efficiency. It also means minimizing total life-cycle costs through low and zero-maintenance materials, and reduced use of non-renewable products during construction," the facility touts on another part of its website.

"Perhaps one of the biggest environmental advantages of Pensmore is its inherent durability. Designed to endure for centuries, the chateau will leave a minimum impact on the environment while other structures are built, demolished and built again and again."

The site explains some of the technology that will be utilized:

Pensmore’s heating system utilizes a cutting-edge technique for harvesting solar heat energy that exploits the vast energy storage potential of its steel reinforced TransForm™ concrete shell. Many builders already make use of traditional solar heat collectors, which are highly efficient at moderate temperatures. But until now, it has been expensive and impractical to "bank" the excess solar heat generated on sunnier days. Pensmore's newly-developed technologies enable it to store millions of BTUs of thermal energy while the sun shines, slowly releasing this "green" heat back into the interior at night and during cloudy days.

Secondary sources of heat include combustion of wood products grown on the estate (net carbon neutral) and "conventional" geothermal systems.

It will also take advantage of a new product called TRransForm -- a super-insulated energy-storing concrete forming system. That's important because Huff is an investor in the product. He told the Times he wants to test out the material on a large scale.

So why rural Missouri?

According to Huff, he wanted to test out the technology in a climate that offers both warm and cold temperatures. But there's also another reason: rural Missouri shields him for building inspections.

"[B]y locating in an area famous for a small government approach," the Times reports, "he is not subject to building regulations or inspection, which he said would have complicated his efforts."

According to the Times, construction has been ongoing for the last two years, and probably won't be completed for another two.