The Riverside Public Library is about to get a major heating and air-conditioning upgrade, with the library board poised to spend between $300,000 and $350,000 to replace its 31-year-old system.

The library board will put the project out to bid in early September, and the installation of a new rooftop unit and upgrades to the system inside the building are slated to take place before the onset of winter, said Library Director Janice Foley.

“This is really important to do right away,” Foley said. “We’re so afraid it’s going to break down during the winter.”

The present heating and air-conditioning unit was installed in 1985 when a 12,500-square-foot addition was put on the original 5,761-square-foot library building, which was built in 1930 and designated a local landmark in 1993.

While the heating and air-conditioning unit was rebuilt in 2007, its control hardware is obsolete, the hardware and computer software that control the system are no longer supported, and the system malfunctions often, according to a report issued in June by Cartland Kraus Engineering, which was hired by the library board to survey the system and make recommendations for improvements.

The engineering report also indicated that in the past two years, the library board has spent $27,000 to maintain the system, “which is considerable and has been escalating.”

In addition, the report noted inadequate air flow on the library’s lower level, the ventilation system in the quiet reading room, a problem with the way the HVAC unit drains condensation, and evidence of a malfunctioning ignition control for the gas furnace.

The report recommends replacing the rooftop unit, which Foley described as being the size of mini-truck trailer, replacing or upgrading the 21 variable air volume (VAV) boxes that distribute air through the supply ducts, replacing the zone temperature controls, and making the air ventilation in the quiet reading room code-compliant.

The engineering firm is also to deliver to the library board an estimate of what a new system will cost to operate.

It’s unclear exactly how soon work will be able to start once the library board has bids in hand, but it ought to begin this fall. Foley said she did not expect there to be much in the way of disruption to library operations as work progressed. Depending on weather, however, there could be a day or two where the library is closed between the time the old unit is disconnected and the new unit connected.

“We’re not planning on closing unless there’s severe weather,” Foley said.

There will a short time that a crane will be located in the east parking lot next to the library. The crane will remove the present unit and lift the new one into place. The presence of the crane in the parking lot won’t affect access to the library by patrons, Foley said, though it will mean temporarily relocating vehicles that village and library officials park there.

The heating and air-conditioning upgrade will be funded in part through a low-interest loan from the village of Riverside, which acts as the library’s corporate authority, since the library, strictly speaking, is not a separate taxing district.

While there’s no intergovernmental agreement in place yet, village trustees at a recent meeting of their board, signaled their support of the loan. Tentatively, according to library board meeting minutes from June, the village would lend the library $200,000 at an interest rate of about 1.15 percent to be paid off over three years.

Those same meeting minutes indicated that the library board had sought a loan from a private lender, but it would have come with an interest rate of 3.5 percent and additional costs to obtain a bond counsel and other fees.

Village Manager Jessica Frances said the loan would be structured in such a way that the interest charged to the library would ensure the village can cover legal and other costs related to entering into the agreement.