Record-breaking temperatures across the state over the summer have the head of the state’s teachers union concerned as nearly 181,000 public school students head back to school Wednesday, following the shortest summer break in at least five years.

“It’s only going to get worse. August and September are the worst months,” Hawaii State Teachers Association President Corey Rosenlee said of the heat. “It’s an unhealthy environment for students to learn in and for teachers to work in.”

Even before being elected president of the 13,500-member HSTA last month, Rosenlee, a Campbell High School teacher, had organized rallies and lobbied the Legislature to help bring attention to Hawaii’s hot classrooms. In his new role, he says, one of his main priorities this year is to see more classrooms air-conditioned.

“You have to add five to 10 degrees to the temperature, so if it’s 90 degrees outside, it could be 95 to 100 in the classroom,” Rosenlee said. “And when you put 20 to 30 kids in a room like that, they’re basically heat-generating machines. The kids are so focused on the heat that they can’t focus on lessons and their bodies literally start to break down.”

Rosenlee said an alternative would be to close down schools when it’s too hot.

“The first priority would be putting AC in the classroom. But if the state is not going to do that, we have to listen to health care professionals and say that if it gets too hot, we have to close our schools,” he said. “Most major cities have heat polices. Hawaii has no heat policy of how hot it has to be before we consider the classroom unsafe. We do not want to close down schools; we want AC.”

Rosenlee said the union will be conducting a survey in the coming weeks of how many public school classrooms have air-conditioning to help determine the overall need across the state.

Among the state’s 256 regular public schools, 16 have central air conditioning, according to the Department of Education, including the newly built Ho‘okele Elementary School in Kapolei. Those schools also have some of the highest utility bills.

For example, Pohakea Elementary in Ewa Beach saw its utility bill increase by 160 percent after installing schoolwide air conditioning.

Rosenlee said he hopes the survey of classrooms will help inform a realistic budget plan. He also wants to see the state consider an energy-efficient alternative such as solar-powered air conditioning.

Department of Education spokeswoman Donalyn Dela Cruz said air conditioning is one of several solutions identified as part of the department’s so-called heat abatement program.

“We’re not just looking at AC,” she said. “When we talk about cooling classrooms, we’re looking at a variety of options that work best for each school. For those classrooms that need cooling systems, we have a priority list. Some schools are more complicated than others because of infrastructure. That’s where we start looking at alternatives — solar-powered vents, ceiling fans, roof painting, insulation.

“To limit the solution to AC assumes that every school can pay for it and that every school is set up with modern infrastructure that can handle an AC system,” she added.

The department has eight schools on its air conditioning priority list, with Ewa Beach Elementary, Ilima Intermediate and Campbell High in the top spots. Six schools have moved off the list over the past decade.

Dela Cruz said the DOE estimates it would cost $1.7 billion to install air conditioning in all of its schools. That doesn’t include the increased cost to operate the systems. The current annual electricity bill for all schools is $60 million.

“There’s a process to this,” she said. “Having a good, comfortable learning environment is a priority. We’re not ignoring the fact that we know there are classrooms that are hot, and we’re working to address that. Funding has a lot to do with it, but it’s not a one-size-fits-all approach.”