Returning to the Hopkinton School Committee on Thursday after a year, representatives from the engineering firm CMTA noted the district must make a decision about its major mechanical systems at the high school.

Jason Volz, CMTA project manager, spoke about replacing the 27-year-old HVAC (heating ventilation air conditioning) system with a more energy efficient option, aligned with the town’s “net zero” goals.

CMTA, which also is working on geothermal systems for the Hopkins and Charleswood projects, said the aim is to remove natural gas from the heating, provide cooling throughout the building and address impending deferred maintenance.

Some common areas like the auditorium and gym have air conditioning while classrooms do not, according to project manager Graham Smith. He said an energy audit showed south-facing classrooms reaching 82 degrees.

There also are signs the chiller is failing, Smith said.

Last year, the School Committee weighed four options — determining a geothermal water-to-water heat pump would be most cost effective and energy efficient.

At the time, the budget cost was presented as $18.9 million, done in two phases: $10.7 million and then $8.2 million.

As of a mid-September, the price increased to $22.4 million, mainly because of mechanical labor that will have to happen inside no matter what type of HVAC system is adopted.

Volz said that amount could change. “The best thing we can do is get more competition with bids,” he said.

Volz said the opportunity for “once in a generation federal tax credits” exists once the project is completed. It would total $7.6 million and not be application-based. Instead, the credits would be “guaranteed as long as we check all the boxes,” meeting the energy goals that are promised.

Those credits only are available through 2031, he said.

MassSave incentives estimated at $1.3 million would be pursued along with grants from MassCEC ($1 million to $5 million) and Green Communities ($500,000), according to the representatives.

Using American-made equipment bumps up credits by 10% as well.

The town would be looking at $19.4 million in estimated credits coming back from three different projects (Hopkins, Charleswood and HHS HVAC), said Volz.

“[It’s] a significant investment you all have made, but there’s a return on [that] investment,” he added.

The plan is for Town Meeting to consider a proposal in May 2027. If approved, work would take place during the summers of 2027 and 2028.

Drilling outside and in the mechanical room would cause minimal disruption during the first summer. However, the high school would become a major construction site during the summer of 2028, according to Smith.

Administrative offices would need an alternate location as would summer programs. Those interruptions would not have a negative impact, said Assistant Superintendent and Chief Operating Officer Jeff LaBroad.

“Some plans are being strategized,” LaBroad said, including in collaboration with the Parks & Recreation Department.

In response to questions from School Committee member Sandra Irwin, Volz explained the “in the ground” geothermal system is a “50-year asset,” while the equipment, like traditional mechanical systems, would have a 20-25-year life span.

“You do have an asset in the ground you don’t have to replace,” he said. “That’s the advantage.”

School Committee member Nancy Cavanaugh asked the representatives to explain how air conditioning would not be an additional cost.

Volz replied, “Geothermal has the ability to do both,” with the system using heating and cooling throughout the year.

LaBroad noted the district would “mark a moment in time” when the system transitions from one to another.

“The ability to have the air conditioning, particularly with shifting of temperatures, is a really good thing for the learning environment,” said Cavanaugh. “But I also want to be respectful of those who are concerned about the bottom line and [highlight] this is not adding to it.”

In response to vice chair Jamie Wronka noting delays to addressing the issue are “risky,” Volz said, “Inflation is real.”