PHOTO: JOHN KIRK-ANDERSON/STUFF Ara tutor Mick Cooke says students like Jamie Coey, left, Joe Tippett, Creed Rickard, learn about sustainable building but some materials are cheaper to buy overseas.

Two tiny eco-houses built by a group of 20 students will soon face the ultimate market test at auction.

The portable houses contain sustainable features that real estate marketers increasingly highlight. Eco-homes advertised on auction site Trade Me range from totally off-the-grid houses, or just better insulated and heated to higher levels than most traditional Kiwi homes.

The money raised from the tiny houses auction will fund several Ara polytechnic students on a week-long working trip to Fiji to help Habitat for Humanity build new homes in cyclone devastated areas.