A client of architect Jim Poteet wanted a guest house to put outside her San Antonio loft building.

"She wanted to experiment with turning this into an artist studio prototype as well," said Poteet, the founder of Poteet Architects.

His solution was a converted 8-foot by 40-foot shipping container.

The project, completed in 2010, was a learning experiment. Poteet toyed with installing a photo-voltaic roof (to generate electricity from solar energy), but found the wattage not sufficient enough to cool the studio on hot Texas summer days.

So, instead, he built a separate "green" roof with plants that keeps the sun off the container and cools the space. Another eco-friendly element: Dirty water from the sinks and shower irrigate the roof.

Poteet never did a complete calculation of how much it cost to build the studio, but estimated that it was probably about around $65,000.