FAIRFIELD — The Board of Selectmen Wednesday unanimously approved $3.9 million more in bonding needed to finish the expansion and renovation project at Fairfield Ludlowe High School.

In June 2013, the building committee overseeing the project won approval for a total of $11.6 million for the project at the Unquowa Road school, which included additional classrooms, new roofing, an expansion of the cafeteria and replacing the windows.

The project was divided into three phases, and the first two phases — the roofing, classrooms and cafeteria — have been completed. However, the building committee did not have enough money left for the window replacement, work that also will require the abatement of asbestos and PCBs.

The cost for the window work, according to Peter Manning, from Gilbane Construction, is $4.1 million, but that is offset by $258,000 remaining in the original appropriation.

Manning said three different plans for the abatement contaminants were sent to the federal Environmental Protection Agency before approval was received in November. The work then went out to bidding by contractors in January.

“The funding we’re asking for now is based on bids,” Manning said, and not conceptual estimates.

Because the bonding request won’t make it through the approval process from town boards before the end of April, Manning said the replacement and abatement work cannot start until the summer of 2017. It will be completed in the summer of 2018.

He said there is a 12- to 14-week lead time to obtain the windows from the time they are ordered. That would push the start of work into the end of July, he said, but the work then would have to stop in August in preparation for the start of the new academic year.

The town is expected to receive about $1 million in state reimbursement to help cover the cost of the window replacement project.