Scarborough voters overwhelmingly approved a plan to borrow $39 million to replace the problem-plagued Wentworth Intermediate School.

The unofficial results of the vote were 4,792 in favor and 2,784 opposed.

Since 2006, the school district has spent $1.3 million fixing up the nearly 50-year-old school, including a recent roof replacement that’s only under warranty for five years because the substructure is in poor condition, said Paul Koziell, chairman of the 40-member building committee that developed the Wentworth proposal.

“It’s a tremendous victory, absolutely,” Koziell said Tuesday night. “We put together the right project, we looked at all the information and the voters agreed with us.”

Had voters decided against replacing Wentworth, as they did in 2006, school officials anticipated spending as much as $2.5 million over the next three years to address problems with the building, including crowding, mold and asbestos-contaminated window casings.

Wentworth was built as a junior high school in 1963. A wing was added in 1974 and portable classrooms were added in 1988. Today, the school has 16 portable classrooms.

The school serves 775 students in grades 3 through 5. It also hosts community recreation programs and its kitchen produces meals for the town’s three other elementary schools, as well as Wentworth students.

The new school will be built beside the existing building, which will be torn down afterward. Construction is scheduled to begin in 2012, with the new school opening in 2014.

At 163,000 square feet, the new school will be about 60,000 square feet larger than the existing building. However, it will be 21,800 square feet smaller than the $38.3 million proposal rejected by voters in 2006.

The new school will feature a $1.4 million geothermal heating and cooling system projected to save $73,500 on annual energy costs.

Moreover, supporters said the existing building is so poorly built, without sufficient insulation or airtight construction, that it costs twice as much to heat than the newer, similar-sized Scarborough Middle School.

Supporters cited a wide variety of problems with the existing building, including groundwater and radon seeping into the basement crawl space, former bathrooms being used as storage and instructional space, fire sprinklers missing from most of the school and rodent infestations in the portable classrooms.

Endorsed by the school board and local chamber of commerce, the project will add about $177 to the annual tax bill on a $300,000 home, supporters said.

Supporters said the project could wind up costing less if it inspires competitive bidding in a hungry construction market and gets a low interest rate when the district borrows money for the project.

A 30-year bond with an interest rate of 4.5 percent would cost taxpayers $27 million in debt service, but the potential for interest rates as low as 3 percent could reduce debt service by $9 million, according to town officials.

Staff Writer Glenn Jordan contributed to this story.

Staff Writer Kelley Bouchard can be contacted at 791-6328 or at: [email protected]