A new law signed by Mayor Kirk Caldwell requires future construction projects to have construction viewing panels built into the wooden barriers that surround a job site.
The ordinance mirrors New York's building code that requires Plexiglas panels every 25 feet so inspectors can scan a site for violations, using the element of surprise.
The same rule will now apply on Oahu.
"With these windows the inspectors can make sure that they're working safely, and if they're not they can go in immediately and rectify the situation," said Tyler Dos Santos-Tam, executive director of the Hawaii Construction Alliance.
The organization represents unionized labor. Dos Santos-Tam believes the law will make job sites safer for workers.
But the president of the General Contractors Association of Hawaii disagrees.
"You're trying to do a task and you see somebody looking at you, you will get momentarily distracted, which is an added hazard to the contractor," Cedric Ota said.
The barrier law aims to curb illegal behavior, like what happened at Ala Moana Center in 2015 when some contractors were investigated for violating labor laws.
"On construction sites there's a lot of opportunities for people to do things that aren't right necessarily," Dos Santos-Tam said.
Opponents included HPD and the city's planning and design departments. They said viewing windows might bring bystanders too close to active construction sites.
"We see it as an increased risk factor and potentially added cost factor that we think will not really benefit the public as much as it is intended to do," Ota said.
He believes construction theft will increase because materials won't be hidden from view.
Dos Santos-Tam thinks thieves are less likely to enter a construction zone if there's the chance someone is watching.
The law does not apply to home construction, agricultural properties, and on projects that can be surrounded by mesh and a chain link fence.