HONOLULU (AP) — Shipping containers: They’re strong, durable and portable, stack easily and link together like Legos. 

About 25 million of these 20-by-40 feet multicolored boxes move through U.S. container ports a year, hauling children’s toys, flat-screen TVs, computers, car parts, sneakers and sweaters.

But so much travel takes its toll, and after about eight years, the containers wear out and are retired. That’s when architects and designers, especially those with a “green” bent, step in to turn these cast-off boxes into student housing in Amsterdam, artists’ studios, emergency shelters,  health clinics.

Despite an oft-reported glut of unused cargo containers lying idle around U.S. ports and ship yards — estimates have ranged from 700,000 to 2 million — the Intermodal Steel Building Units and Container Homes Association puts the number closer to 12,000, including what’s sold on  Craigslist and eBay.

HyBrid Architecture in Seattle, which has built cottages and office buildings from containers for close to a decade, coined  the term “cargotecture” to describe this method of building. Co-founder Joel Egan warns that although containers can be bought for as little as $2,500, they shouldn’t be seen as a low-cost  solution to the housing crisis.  ”Ninety-five percent of the cost still remains,” he says.

A Honolulu City Council committee has approved a proposal to explore the viability of using shipping containers for low-cost housing — an idea already embraced by the mayor.

The Public Health, Safety and Welfare Committee gave a thumbs-up Tuesday to a resolution urging Mayor Kirk Caldwell to develop a demonstration project using shipping containers, the Honolulu Star-Advertiser reported.Caldwell announced last week he’s ready to work with council members and the Faith Action for Community Equity group on affordable housing options, including containers.

The resolution calls for the administration to submit a list of potential sites for the project by May 1.

George Atta, the city’s planning and permitting director, said he already has spoken with several entities about using shipping containers as homes. He said land use laws allow homes made from containers that have basic housing criteria, such as insulation and window openings.

“A number of things need to be checked out before we can say, ‘This is a proper use of a shipping container,’” Atta said. “But the potential is there.”

Several portable-housing entrepreneurs urged council members to consider other types of affordable housing.

John Rogers, owner of Affordable Portable Housing, has built residences from shipping containers and other materials. Modular homes are more cost-effective, Rogers said.

A typical 40-foot container has about 320 square feet of space. Turning one into a home can be done for about $32,000, including electrical work and plumbing, according to Rogers.

Craig Chapman, owner of Small Homes Hawaii, also favors modular homes. But regardless of materials used, a demonstration project is a good idea because it would allow community members to accept them as visually pleasing and properly maintained, Chapman said.

“This is something that is really sorely needed,” he said.

Committee chairman Ron Menor said shipping container housing is just one option the city should consider.

Hawaii will need 24,000 homes to meet demand in the next 15 years, housing officials estimate. Of those, 75 percent would need to be in the affordable category.