ROCKLAND, Maine — Rockland taxpayers were shelling out $58,000 a year to heat the public library during the winter and to keep it cool in the summer.

But a six-week energy efficiency project that was completed this week is expected to save property owners at least a cool $11,000 annually.

Rockland City Councilor Larry Pritchett, who also is chairman of the city’s energy committee, was on hand Wednesday as Rockland-based Evergreen Home Performance conducted a final air test to determine how well the insulation and sealing project had gone.

Before the work began around Christmas, about 25,000 cubic feet of air was being exchanged each minute from the 109-year-old library and its newer addition. That air has to be heated or cooled depending on the time of the year. On Wednesday, after the final patron had left the building, another air test was done and the air flow had been reduced to 11,300 cubic feet a minute — a 55 percent reduction.

The energy committee determined a few years ago that the library used more energy than any other city building except for the wastewater treatment plant. Energy-efficiency equipment changes were made to that treatment plant and then the energy committee turned its attention to the library.

In November 2009, the energy committee made its recommendations for the project at the library.

Library Director Amy Levine also was on hand for the final air test and noted how she is looking forward to a more comfortable place for the employees and patrons. She noted that the staff had to use space heaters under the reference desk and that the children’s room also was chilly in the winter and very, very warm in the summer.

The original 9,000-square-foot library was built in 1903 as one of 1,500 Carnegie libraries in the United States. In 2001, an addition was constructed. The older wing had almost no insulation and even the new section did not have sufficient insulation. Pritchett noted that oil prices were not as high when that work was done and that is likely why insulation was not considered a priority at that time.

According to the Maine Office of Energy Independence and Security, the average price for home heating oil in late 2001 was down to $1.10 a gallon. The city is paying $3.19 a gallon this year. The average number of gallons used at the library each year has been 8,375, and the most used in one year was nearly 10,000 gallons.

The city estimates it will recoup its $73,000 investment in the library project in no more than seven years, less if the price of oil continues to rise.

Pritchett said the next goal at the library is to make changes to the heating and cooling system to realize more savings. He expects that once upgrades are made to the system that the $58,000 annual costs for oil and electricity will be cut in half.

Evergreen Home Performance President Richard Riegel Burbank said he was pleased with the outcome of the project.

“This was a very complex project, and very important as well,” Burbank said.

The new insulation included fire-protection spray foam around the top of the foundation, highly mold- and moisture-resistant mineral wool in the wall cavities and dense-packed cellulose in the numerous attic sections of the library, he noted. Disruptions to the activity at the library were minimal, he noted.

Pritchett said he closely monitored the project and this was the best one done that he has seen.

He said the rising price of oil has resulted in greater demand for the services provided by Evergreen. He said while higher energy costs make it economically sensible to do energy efficiency projects such as insulation, the No. 1 reason is something much more basic.

“People want to be comfortable,” Burbank said. “Being cold really motivates people.”

The company president said it was good to be able to hire talented people from the unemployment ranks to do important work such as was done at the library.

Pritchett noted that it is difficult for municipalities to spend money in difficult economic times but that this job has showed that it does make sense.

“There are not many projects where you can take $25,000 out of the budget and get better service,” he said.