It might sound strange, but radiant floor heat is crucial in preventing damage to commercial freezers.

Jim Johnson (left) and Bruce Wikstrom (right) of Earth Energy Systems standing beside the electric boiler and manifolds of a large commercial freezer building in Puerto Rico. The two, plus Jeff Jannetto (not pictured), installed the radiant heating system under the concrete floors to keep ice from forming under the floors and pushing them up. Photo credit: Jeff Jannetto/Radiant Northern Floors

Radiant under-floor heating and commercial freezers may not seem like a natural fit, but to food companies that keep a lot of frozen inventory, the combination can solve a big problem and save them thousands of dollars.

Even though the concrete floors in these freezers have insulation, the insulation doesn’t stop condensation, saysJeff Jannetto, hydronics manager at Lino Lakes, Minn.-based Northern Radiant Floors, a division of Northern Wholesale Supply ( When a bare concrete slab gets cold, the moisture in the soil below will start to gravitate toward that cold spot and turn to ice. Over a few years, a large ice ball begins to form under the floor. As the ice expands, it will crack or push the floor up.

“Those ice balls can lift the footings off the building,” he says. “I’ve seen them go as high as four feet. It can cost a food distributor thousands a day to get the product out of there because it can’t be removed with fork lifts. Then refrigerated trucks need to be rented to store the food while the floor is being fixed.”

Jannetto started working on frost-proofing projects in 1998. Before he became a radiant heat specialist, he worked in the refrigeration field, so he knows how these big freezer systems work. On his first frost-proofing job, Jannetto was called in on a system that had broken down. He reviewed the existing system and applied his radiant heating knowledge to improve the design.

“I didn’t invent the frost-proofing system, I just took it to a new level by adding controls,” he explains. “It’s fun to do something different with radiant.”

A portion of the 50,000-square-foot commercial freezer building in Puerto Rico.

The sugar in food items - such as bakery goods, juice and ice cream - is the hardest thing to freeze, Jannetto says, so it’s crucial that commercial freezers stay at the right temperature. Refrigeration contractors from around the country approach Jannetto and Northern Radiant Floors to design a frost-proof system for their specific needs as well as supervise the installation; he passes on leads to one of three Midwest radiant contractors he works with regularly so the contractor can bid the project. Jannetto also becomes part of the crew installing tubing and piping the boilers.

His designs have evolved as radiant technology has evolved. Today, he uses an injection system with tekmar controls to regulate the temperature of water going into the floor - about 95 degrees F. The purpose is to eliminate the humidity from under the floor so it is dry, he says, not to raise the temperature of the freezer floor itself. That would add to the refrigeration load and cost more money to run.

“We control the amount of heat we put into the floor and we control the return temperature, which is related to the temperature under the slab,” Jannetto explains. “That’s what turns the system on and off.”

Progress on the radiant floor as tubing is laid down.

Hot Job In Puerto Rico

A recent job in Puerto Rico involved contractorBruce Wikstrom, owner of Siren, Wis.-based Earth Energy Systems ( The project was planned about two years before work started.Eurgel Berry, president of Blain, Minn.-based Thermal Construction Specialists (, approached Jannetto about designing a frost-proof system for a big food distributor in Puerto Rico.

“When Eurgel bids a freezer job, he calls me to bid the frost-proofing system,” Jannetto explains. “He knows how important it is that the floor doesn’t freeze and bust up. He includes our work in his scope of work and he warranties the vapor barrier around the freezer, which is critical to a freezer application.”

Installation of the freezer wall panels from Thermal Construction Specialists.

Normally on a freezer floor there’s 6 inches of polystyrene insulation above the radiant heating system, Jannetto says. The radiant tubing is either imbedded in a slurry slab (a 2-inch slab of cement) or buried in sand. The sand is watered and then tamped down so it’s as hard as concrete. A vapor barrier is then installed, followed by the 6 inches of insulation before the concrete freezer floor is poured.

“That layer of insulation under the slab keeps the dirt warm,” Wikstrom says. “Heat drives the moisture away so it keeps the soil dry and maintains the integrity of the slab.”

Once Berry’s team started putting the freezer wall panels in and completed the prep work, he called Jannetto and gave him the general contractor’s schedule. After a few delays, Jannetto, Wikstrom andJim Johnson, also of Earth Energy Systems, started the radiant floor portion of the job this past March. Johnson is a sheet metal fabricator, but he wanted to check out the tubing side of Earth Energy’s business.

The radiant team had shipped all their tools and equipment (including uncoilers and twist-tie tools) to the island about two months before; they had figured on an earlier start, Wikstrom explains. It took them about nine to 10 days to complete the job, working with and around the other trades.

“You’ve got to be pretty flexible,” Wikstrom says. “Every day we were putting down tubing or piping boilers or something else, while dealing with the heat and humidity at the same time.”

The main problem on the project was the language barrier and trying to coordinate with the other trades on the jobsite. The first day, after a safety meeting, Jannetto and Wikstrom went to check the site where they were supposed to start tying down the radiant tubing. “None of the final grade had been done on the freezer and none of the mesh had been laid, so we couldn’t get going,” Wikstrom recalls. “There were numerous holes that had to be drilled through a 6-inch concrete footing, so we started drilling the holes for something to do.”

The electric boiler and associated plumbing to the two separate radiant floors. The manifold on the right serves a 16,000-square-foot freezer and the unfinished manifold to the far left serves the larger 35,000-square foot freezer.

The other trades were very accommodating and easy to get along with, he adds, even though they spoke only Spanish. By the second day, some of the ground had been compacted and mesh laid down so the three-man radiant team could start work.

They laid out 23,000 feet of private-label 3/4-inch tubing between two buildings totalling about 50,000 square feet. The Thermolec electric boiler was wall-mounted on the outside of the building.

Jannetto handles about a dozen of these projects a year, while Wikstrom has about 20 projects under his belt. The size of the job is always different, but they are usually for manufacturers or large food distributors.

“I’m providing a foolproof, state-of-the-art radiant system so the food manufacturers or distributors don’t have to worry about their food,” Jannetto says. “Basically, these types of radiant systems are big dehumidifiers. As long as the freezer floor is a few degrees warmer than the dirt on the outside of the freezer, the moisture won’t go there and the floors will be fine. I don’t want to have to go back to Puerto Rico to fix a broken system!”