From Steam Heat to Geothermal: Holy Trinity Catholic School's Summer Transformation
by Diocese of Des Moines Catholic Schools | March 31, 2026
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The morning the teachers walked back into Holy Trinity Catholic School's B Building after summer break, something was different. Every window was clear. No bulky air conditioning units wedged into the sills, no cords snaking across the glass, no hum and rattle competing with the morning quiet. And the air itself? Cool. Comfortable. Just right.
For a building that had spent the better part of 65 years either boiling or freezing its occupants, it felt, as one staff member put it, like heaven.
A Building That Deserved Better
Built in 1958 alongside Holy Trinity's classroom building, the B Building has served the school community in many forms over the decades, originally as a convent housing the nuns who taught at the school, and eventually becoming home to music, a STEM lab, preschool classrooms, staff offices, the school counselor, learning support staff, and the youth ministry.
But for all its importance to the life of the school, the building had never been comfortable. Heat came from steam, piped over from the church boilers. Cooling came from window air conditioners. These units ran, counterintuitively, all year round because the steam heat was so difficult to regulate.
"Our maintenance guy had to go down into the boiler room and pull a chain to open and close the steam valves if you wanted to try to adjust the temperature," recalled Mary Gisler, business manager for Holy Trinity Catholic Church and School. "Steam just sounds a little out of date, but it was what we had."
Teachers endured it. Students endured it. And year after year, the question of what to do about the B Building lingered, answered only by the hum of window units doing their imperfect best.
Seeds Planted Two Decades Ago
The story of this summer's transformation actually begins around the year 2000, when Holy Trinity undertook a capital campaign with an ambitious vision for new construction. The campaign fell short of its goal, but rather than walk away empty-handed, parish leadership made a pivotal decision: invest in geothermal heating and cooling for the classroom building.
And then they did something remarkable. They planned ahead.
Knowing they couldn't afford to bring both buildings onto geothermal at once, they deliberately installed a system large enough to eventually support the B Building, too. They left physical space in the ground for additional wells. They built connection points into the walls, two large input places, ready and waiting. They sized the circulating pumps to handle the future load.
"It was good foresight," Gisler said. "It did save us money, doing it then as opposed to doing it now."
For more than two decades, those connection points sat quietly in the walls of the B Building, patient as a promise.
Decades-Old Injustice
When B Building was built, the pastor at Holy Trinity did not want to install A/C in the convent, Gisler said.
Decades later, the church and school’s current pastor, Fr. Mark Neal, identified the B Building as the target of the next improvement project, which he said “corrects a decades-old injustice.”
Fr. Neal realized a pool of funds from the Employee Retention Credit (ERC) was sitting in CDs, and the 179D federal tax credit — a deduction available to tax-exempt organizations that make qualifying energy-efficiency improvements — was still within reach.
With approximately $500,000 in ERC funds plus earned interest available, and the 179D window beginning to close, Holy Trinity set a timeline: work would begin the day school let out for summer.
Navigating the Process … and an Unexpected Pivot
Getting there wasn't without its detours. The original plan called for traditional heat pumps, a proven, long-standing technology, but after investigating questions by the building commission and navigating the diocesan approval process, the supply chain shifted dramatically beneath them.
By the time all approvals were finally in order, the lead time on those heat pumps had jumped from four weeks to 20. They wouldn’t arrive until well into the school year.
With demolition already underway, Holy Trinity had to pivot. They selected an alternative solution: variable refrigerant flow (VRF) technology, which would work perfectly in tandem with the existing geothermal wells. Those 20-year-old plans came to fruition.
VRF is a newer technology, Gisler notes, and the efficiency gains and the outcome have been impressive.
"It's working really, really well," she said.
How It All Works
For anyone unfamiliar with geothermal systems, the concept is elegantly simple. The earth, just below the surface, holds a nearly constant temperature of around 50 degrees Fahrenheit. In summer, heat from the building is transferred down into that cool earth, where it dissipates. In winter, the system pulls that 50-degree warmth up and adds only enough energy to bring it to a comfortable room temperature.
"You're warming your fluid up to 50, and then you only have to heat it from 50 to 70 in the winter," Gisler explained. "Or vice versa in the summer. So it's more energy efficient."
Because the geothermal well field was already drilled and the circulating pumps were already in place from the 2000 installation, the primary new work was drilling additional wells to support the B Building's load and running refrigerant lines throughout the building, which lead to heating/cooling VRF units in the rooms. They also installed a new rooftop unit that brings in and conditions fresh outside air, now required by code.
A Summer Sprint
Work began the moment the last school bell rang in June, and the crew delivered. By the time teachers returned to set up their classrooms, the B Building had been transformed. New systems. New air. And clear windows, for the first time in anyone's recent memory.
The day before school started, staff from across the building pitched in, helping teachers haul furniture back into place, cleaning rooms, and getting everything ready. A professional cleaning company was brought in to make sure the building was truly move-in ready.
The reaction has been unanimous.
"The feedback I've gotten from the staff has been really, really positive," Gisler said. "They're like, 'This is heavenly. We can control it. It's not boiling.'"
Teachers also noted something they perhaps hadn't fully anticipated: light. With no window AC units blocking the glass, rooms that had felt dim and cluttered now feel open and bright.
Stewardship That Works
After installing the necessary software, including updates to dated, inaccessible software that controlled heating/cooling systems in the other buildings, the total project cost came in at approximately $800,000. Some of the software upgrades were paid for with the school building fund, but the majority was funded by ERC tax credit proceeds, government money that Holy Trinity had received and set aside.
When the 179D tax credit is processed, Gisler estimates the return could be close to $200,000, which will flow directly back into the school building fund for future projects, like the new windows planned for next year to replace the original 1958 panes still in place.
It's the kind of stewardship that makes a project like this genuinely remarkable: a building that needed help for decades, infrastructure that someone thought to put in place 20 years ago, a funding opportunity that almost closed, and a community that moved quickly enough to catch it.
What Comes Next
The B Building's transformation isn't quite finished. New windows are planned for next year, which will make the system even more efficient and bring long-overdue brightness to classrooms. A broader refresh, including paint and updated finishes to provide a more welcoming feel, is part of the longer-term vision.
But for now, on a fall morning when the preschoolers are settled into their rooms, the STEM lab is humming, and the school counselor can meet with students in a space that's finally, genuinely comfortable. The work feels complete.
Sixty-five years of waiting. One well-planned summer. And a school community that is, at last, cool.