A few of Hawaii’s top-grossing contracting firms have joined the mix of companies preapproved to bid on projects for the state’s “cool schools” initiative as the pool of qualified companies has doubled to 36 from 18 contractors.

The expanded pool is expected to help attract more competitive bids after the Department of Education last month announced that initial proposals had come in over budget for projects at six schools. The high bids — including one that was nearly 10 times the per-classroom estimate the department had been using — prompted the state to halt the awarding of bids and led one state lawmaker to ask the attorney general to investigate possible collusion among the contractors.

The DOE on Friday released the names of the 36 companies and said it is preparing to put the projects back out to bid.

Included among the newly qualified contractors are Nan Inc., Isemoto Contracting Co., Shioi Construction and Ralph S. Inouye Co. — companies that rank among the 20 highest-grossing general contractors in Hawaii. The initial round of contractors included smaller, lesser-known firms.

“We appreciate the attention and effort by our local contractors who have come forward to work on our sustainable cooling projects,” Dann Carlson, assistant superintendent for school facilities and support services, said in a statement. “Cooling classrooms is much more than just installing an AC unit, it requires professional contractors who can complete a job the right way. This includes ensuring electrical capabilities, properly sealing rooms, and more.”

The ambitious plan to cool 1,000 classrooms — pledged by Gov. David Ige in his State of the State speech and subsequently funded by the Legislature — initially was envisioned to be completed by December, and officials had hoped some of the work could begin over the summer while most classrooms were empty. But with the work being rebid, and the new school year set to begin Aug. 1, the project will likely be delayed well into next year.

Using early industry estimates, department officials had budgeted $40,000 as an “estimated median per classroom” cost to cover equipment and installation of air conditioners and other heat abatement measures. As recently as May the DOE had said it expected to complete the project for roughly $45 million, with most schools receiving solar-powered air conditioners to offset energy use.

But procurement documents show the priciest per-classroom proposal came in at $360,770 to install solar-powered air conditioning in one portable classroom at Ewa Beach Elementary. (By comparison, solar-powered air-conditioning projects were recently completed at Farrington High and Kaunakakai and Kilohana elementary schools on Molokai for between $10,000 and $26,000 per classroom, including donated equipment.)

The 1,000 classrooms targeted for the cooling initiative are in 33 schools deemed to be the hottest in the state. Consultants for the DOE analyzed those schools to come up with the design plans that contractors are bidding on. The DOE on Friday said the projects include a mix of photovoltaic (solar-powered) air conditioning, with both PV and electrical power; solar air conditioning with battery power; and standard split-system air conditioning with full electrical power.

The legislation providing $100 million for the work requires spending the funds on “equipment and installation costs for air conditioning, other heat abatement measures, energy efficient lighting, and other energy efficiency measures” to help offset energy use.

In anticipation of the funding, the DOE in March began pre-qualifying contractors. Of the more than 3,000 contractors that were notified, 18 firms qualified. In May the DOE reopened the pre-qualifying process to attract more contractors; 18 more companies qualified. The DOE vetted general contractors with A or B licenses that have been in business for at least five years and have good safety records.

The department says it will be meeting with the qualified contractors to review project specifications and a timeline for bidding.

While DOE officials have pointed to increased labor costs due to the state’s construction boom and the initially limited number of companies that were pre-qualified to bid for the high proposals, some general contractors contend that the department’s project specifications are overly complex.

For example, the specifications for a heat abatement project at Waialua High & Intermediate, one of the 33 schools on the priority list, are some 1,800 pages long. The printed documents stack roughly a foot high.

“We’ve seen specifications this thick on a $300 million, $200 million condominium, and here we have a heat abatement project for DOE,” Glen Kaneshige, president of Nordic-PCL Construction, told the Honolulu Star-Advertiser editorial board.

“I think we need to get out of our mind that heat abatement … is an air-conditioning unit hanging off the wall,” said Kaneshige, whose company is not bidding on the cooling projects. “It’s everything to do with getting heat away from classrooms.”

Air conditioning is one part of the DOE’s heat abatement program, which also includes installing ceiling fans, solar-powered vents to draw out hot air, insulation, shading and heat-reflective roof systems. The department’s goal is for classroom temperatures to be at 76 degrees.