University of Colorado's entry

The winner of the last two competitions in 2003 and 2005 was the University of Colorado at Boulder.

This year, the team is focusing on modularity and flexibility. They built a house according to the competition's specifications--sized about 800 square feet--but the design allows it to be expanded to 2,200 square feet, the size of a typical family home, according to the project's student lead, Chad Corbin, who is pursuing a master's degree in building systems.

Corbin and his cohorts have worked on the structure for months--Corbin himself has spent more than a year and half on the competition.

On Thursday of last week, only hours before the tours started, Corbin and his colleagues were still assembling the house. "I'm going on three or four hours a sleep a night, and me and another guy pulled two consecutive all-nighters," he said.