The city is waiving about $10,000 in sewer and permitting fees to encourage homeowners to apply, and about 120,000 lots on Oʻahu could accommodate an extra unit, Caldwell said. To date, the city has approved about 150 out of nearly 1,400 applications. Nearly 250 were denied, mainly because the properties couldn't support additional sewer needs, he said.

“It’s a way to build affordable housing without a government subsidy, and that's pretty much un-heard of,” said Gavin Thornton, co-executive director of the nonprofit Hawaiʻi Appleseed Center for Law & Economic Justice. “It’s not going to solve the affordable housing crisis by any means, but it is a piece of the puzzle.”

Thornton’s group partnered with Habitat for Humanity Hawaiʻi to build the home on the Capitol lawn, relying on volunteer builders and donations of lumber and supplies from local companies.