The refrigeration system beneath the rink is only half the job. Above it, roughly 18,000 people, open doors, concert lights, and a 675,000-square-foot building are all trying to change the temperature.
Ball Arena in Denver. Photo by Troutfarm27, licensed CC BY-SA 4.0.
The first major event at Ball Arena was not a hockey game.
It was a Celine Dion concert on October 1, 1999.
That feels appropriate for a building that has spent its life changing identities. One night, it is an NHL rink. On another it is an NBA court. Then somebody builds a concert stage over the ice, fills the bowl with lights and haze, and asks the building engineers to make the air behave differently than it did the night before.
The Colorado Avalanche make Ball Arena look like a hockey building. The ice crew makes it look inevitable. Neither impression is quite true.
Ice inside an arena is a temporary victory over heat. It sits beneath thousands of bodies, television lights, and a roof covering more than 675,000 square feet. Every open loading-dock door brings in outdoor air. Every concert adds equipment, people, and a new list of temperature requests. Even when the ice is hidden beneath a basketball floor, it is still down there exchanging heat with the building.
Keeping it playable requires two mechanical worlds to work together. One is beneath the slab: chillers, pumps, glycol and controls. The other is above it: air handlers, outside air, exhaust, humidity, and pressure.
The interesting part is what happens where those worlds meet.
Before the puck drops
An Avalanche game inside Ball Arena. Photo by Murphpics, licensed CC BY-SA 4.0.
Danny Nichols is Kroenke Sports & Entertainment's Executive Director of Engineering and Sustainability. His responsibilities extend beyond Ball Arena to other KSE properties. Still, in an interview with the Rocky Mountain Mechanical Contractors Association, he described what his crew does before an Avalanche crowd arrives.
They start pulling the arena bowl down to about 55 or 56 degrees.
Once the doors open, the crowd does the rest in the wrong direction. Thousands of warm bodies enter. Concessions run. Lights come on. The bowl temperature rises quickly toward 60 degrees. Nichols said the crew tries to keep it below roughly 64 degrees during hockey because warmer conditions can soften the ice.
In January, Denver may give the engineers some free cooling. Outside air can help carry the load.
The playoffs are another matter. Nichols described late-season games with outdoor temperatures near 100 degrees, while the bowl remained around 60 degrees. That is a serious temperature difference across a building whose doors keep opening.
Two built-up air handlers serve the arena bowl. Nichols put each at about 175,000 cubic feet per minute. About fifteen more air handlers serve the concourses, offices, and other spaces.
Those numbers are big, but the problem is familiar to anyone who has worked on a small commercial system. The occupied space changes faster than the equipment can. By the time a sensor notices the crowd, the crowd is already there.
The ice beneath the concrete
The rink begins below the surface people see.
Refrigerated glycol moves through piping beneath the concrete slab. A Denver Water profile of longtime ice manager Tony Kreusch described the slab as being held around 14 degrees. Water is then frozen in thin layers rather than dumped into place all at once.
The crew first creates a base. A white layer gives the rink its clean appearance. Lines and logos are applied, then sealed under more water. The finished sheet is typically about 1¼ inches thick.
That is not much room for error. Too thick, and the refrigeration plant has to work through unnecessary ice. Too thin, and skates can reach paint or concrete.
The water matters too. Ball Arena has used reverse-osmosis water because dissolved minerals and trapped air can affect clarity and hardness. In a 2014 interview, Kreusch said a typical game day could include as many as ten resurfacing cycles and use about 3,000 gallons of water. The resurfacing water was heated to roughly 140-160 degrees so it would flow into the skate cuts before freezing.
Hot water on ice sounds backward until you think about the job. The goal is not merely to freeze water. It is to leave behind a thin, smooth repair.
Kreusch also made a point in a later Zamboni interview that applies far beyond rinks: ice is forgiving, but you need time.
Mechanical systems are forgiving in much the same way. If you notice the problem early enough, you can usually make an adjustment. If the building is already full, the schedule is added to the load.
When the rink disappears
Ball Arena does not remove the ice for every basketball game or concert. Crews cover it with roughly 600 one-inch fiberglass panels.
Nichols described the panels as approximately four feet by eight feet. A normal changeover takes about four hours. When the schedule gets ugly, the crew has completed one in roughly two to two and a half hours.
Once the floor is covered, the refrigeration cycle changes. Nichols said the ice plant can start at a slab temperature near 19.1 degrees and pull it down to about 16 degrees in roughly an hour. Then the plant may remain off for around four hours while the panels insulate the surface. With the ice exposed, it gains heat faster, and the plant may cycle again in about two hours.
The covered rink is not out of mind. Kreusch said spills at concerts can work through joints in the panels and reach the ice. By the time the floor comes up, the crew may find divots or other damage that has been hidden for days.
That is one of the least glamorous parts of arena work. The show leaves town. The trucks leave the dock. Somebody stays behind to find out what happened underneath it all.
Denver's dry air helps, until it doesn't
Humidity is one of the biggest enemies of arena ice. Moist air can condense near the surface, create fog and add frost. Denver's climate gives Ball Arena an advantage compared with buildings in wetter cities.
Kreusch has said the region's low humidity, water quality and steady winter conditions are all helpful.
Dryness creates a different problem when the ice is covered. Water can slowly leave the sheet. The ice can shrink, pull away, or develop weak spots while nobody can see it. A climate that makes the building easier to dehumidify can make the rink harder to preserve under a temporary floor.
There is no single perfect humidity number that solves an arena. The right condition depends on the event, the outside air, and whether the ice is exposed.
When a concert wants less air
Depeche Mode at Ball Arena in November 2023. Photo by MerleEllaPatsy, dedicated to the public domain under CC0 1.0.
A hockey game wants cold air moving through the bowl. A concert may ask for almost the opposite.
Touring productions use haze, so beams of light become visible. Too much supply air can push that haze away from the stage and into the concourses. Air movement can also interfere with pyrotechnics. Nobody wants a flame effect leaning toward the audience because a diffuser is doing its job.
Nichols described a balancing act. His crew can pressurize the concourses, slow the bowl fans, and adjust the exhaust so the haze stays where the production wants it. What they cannot do is simply shut off ventilation in a packed arena.
Some touring crews still ask for no moving air over the stage. That request makes sense from their side of the curtain. It does not make 18,000 people stop breathing.
What I take from that is simple: air does not care what the concert rider requested. It follows pressure.
The building has to satisfy both the show and the people inside it. Most spectators never know that negotiation is happening.
Two kinds of chillers
Ball Arena's comfort-cooling plant and ice plant do different work. Both use compressors, condensers, evaporators, and controls, but they do not live the same life.
The air-conditioning chillers respond to people, outdoor temperature, and changing building loads. The ice chillers hold a slab cold for long periods and must recover it on an event schedule.
Before the 2019–20 NHL season, one Trane ice chiller was converted from R-134a refrigerant to R-513A, sold by Chemours as Opteon XP10. According to a Chemours case study, the conversion involved changing the refrigerant, compressor lubricant, and controls rather than replacing the entire chiller.
Ball Arena's redundant chiller arrangement created an unusual comparison. A third party logged two similar machines under operating conditions. The converted machine averaged a measured load of 102 tons. The R-134a machine averaged 104 tons. Both averaged 0.91 kilowatts per ton.
In other words, the published test found similar efficiency and capacity. The main reported gain was refrigerant impact. The case study listed a global-warming potential of 631 for R-513A and 1,430 for R-134a, a reduction of about 56 percent.
Those numbers deserve a boundary around them. Chemours sponsored the case study, even though a third party gathered the energy measurements. The figures describe the measured machines during the test, not every possible operating condition. The document also does not establish the present refrigerant status of every chiller at the arena.
Still, the project shows what retrofit work usually looks like. The old equipment does not vanish because a cleaner option exists. Someone has to make the new refrigerant work with the compressors, lubricant, controls, piping, and schedule already in the building.
Retrofits are rarely as clean as the diagrams drawn for them.
There is always an existing pipe in the way.
Heating and cooling at the same time
The most surprising thing Nichols described was not how cold Ball Arena gets. It was how much heating can happen at the same time.
During certain events, the ice plant can run hard while the building's boiler plant sends out water as hot as 180 degrees. Nichols described days with temperatures around 45 to 50 degrees outside when the chillers were operating at full load, and the boiler plant was also operating.
That is not necessarily a control failure. The rink still needs refrigeration. The concourses, offices, and perimeter spaces may need heat. Outside air still has to be conditioned. One large building can have a winter and a summer happening in it at once.
Nichols discussed the possibility of capturing heat now rejected from the ice plant and using it on the heating side. It was an idea being explored, not a system he said was already operating.
The opportunity is easy to see. A refrigeration plant does not destroy heat. It moves it. If the building is paying to reject heat at one plant while paying to make heat at another, recovery may be worth studying.
The hard part is getting the temperatures, loads, piping, and timing to line up. Useful heat is not always useful when it becomes available.
What the utility numbers can and cannot tell us
Denver's building performance records provide a whole-property view of Ball Arena. For 2024, the reported property used about 12 million kilowatt-hours of electricity and 27,935 million Btu of natural gas. Total site energy was about 68.8 billion Btu, with a site energy-use intensity of 97.5 kBtu per square foot.
The same record lists a baseline EUI of 90.5 and a 2030 target of 63.4.
Those figures are useful, but only at the scale they were reported. They cover the property, not just the ice plant or HVAC equipment. They cannot tell us how much energy went to refrigeration, kitchens, lighting, concerts, offices, or a deep playoff run. The reporting area also differs from the arena's public description, another reason not to force the numbers into a precision they lack.
An arena's calendar matters. A year with more events can use more energy even if a plant operates better. A warm playoff season is not the same as an empty January. Whole-building data can show direction over time. It cannot explain the whole building by itself.
The people between the systems
Nichols did not begin his career with a polished sustainability title.
In the RMMCA interview, he described working for a millwork company before a burst pipe and flood changed his direction. He became a utility engineer, moved into HVAC as an apprentice, and taught himself the refrigeration cycle. He learned an older Tracer Summit control system by following the sequence through VAV boxes, air handlers, pumps, and chiller proof-of-flow.
That is a familiar route into the trade. First you learn which piece failed. Then you learn what had to happen before that piece could run. Eventually, the building starts to look less like a pile of equipment and more like a conversation.
During events, Nichols said the engineering staff includes an HVAC engineer, a carpenter, and an audiovisual technician. Their best nights may be the ones the crowd never notices.
He gave a fine example. During a live Nuggets game, a valve failed while a boiler pump was being replaced. Roughly 5,000 gallons of water and glycol spilled backstage. The game continued. The spectators had no idea.
That may be the clearest explanation of arena maintenance I found.
People watch the puck, the ball, or the stage. Behind the doors, somebody is isolating a line, moving water, checking temperatures, and trying to keep one bad valve from becoming everybody's problem.
The cold part is only half the story.
I started looking into Ball Arena because I am an Avalanche fan and I work in HVAC. I expected the ice plant to be the star.
It matters, of course. The glycol has to move. The compressors have to run. The slab has to stay cold.
But the ice is also protected by air handlers high above the seats, by an operator watching humidity, by a crew laying hundreds of floor panels, and by engineers making changes before a crowd walks through the doors. It survives basketball games, concerts, open docks, and Denver weather because so many people keep giving it attention.
The next time the Avalanche skate out, the ice will look simple. That is probably the compliment the crew wants.
It means the complicated part stayed out of sight.
Research notes and sources
- Ball Arena: About the arena
- Denver Water: “Nice ice, baby”
- Zamboni: Ask the Zamboni Experts, Episode 089, Tony Kreusch
- Chemours: Ball Arena Opteon XP10 case study (PDF)
- City and County of Denver: Energize Denver benchmarking data
- Rocky Mountain Mechanical Contractors Association interview with Danny Nichols
The RMMCA interview and Zamboni video were reviewed directly. Technical details attributed to Nichols and Kreusch were transcribed from the recordings and paraphrased here. No site visit or original interview was conducted for this article.
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