Ranked by ENR as the 24^th largest contractor in the nation and 24th in “green contractors,” JE Dunn Construction Company has worked on a wide range of jobsites and in varied conditions throughout the United States. Yet, for even a seasoned contractor in business for more than 80 years like Dunn, there are the occasional applications that put a company’s abilities and expertise to the test. One where they have to dig deep into the equipment war chest to ensure a project is efficiently completed on schedule and within budget.

A recently completed office expansion project in Fargo, N.D., was one such project for Dunn. In just shy of 20 months, the contractor constructed two office buildings: one at 145,000 ft² and the other 17,000 ft². The larger of the two was a “green” project, earning the company LEED credits.

Crew members worked through the long, harsh Fargo winters with ambient temperatures dropping below -30° F and wind chills reaching -50° F. “In 2008, we faced record cold and snow,” recalls Dean Hanson, project superintendent for JE Dunn.

Working through the winters, Dunn’s crews required equipment that could thaw frozen ground and, once footers were dug, make sure they did not freeze when exposed to subzero temperatures. “We had frost to 5 ft deep and footings that were exposed for up to two weeks at a time,” Hanson mentions.

Once the office was enclosed, Dunn also needed tools to provide clean, dry heat that would not only provide consistently warm temperatures throughout the structure but also help reduce inside moisture in order to help the company earn LEED credits. “The structure is glass from floor to ceiling, so we could not use direct fired heaters,” he adds. “Since this was a LEED project, we could not run the building’s heating system during the construction process.”

Pureheat™ Prescription
Remarkably, to handle these varied heating challenges, Dunn needed only one type of equipment. The company worked with the Wacker Neuson Climate Control equipment dealer in Fargo, Bierschbach Equipment & Supply, who has in-depth knowledge of the challenges contractors face during the winter. The dealer rented Dunn four Pureheat hydronic heaters and multiple HX200 Heat Xchangers™ for the winter months. “We also had another dealer quoting the same type of equipment made by a different manufacturer, but Bierschbach’s quote was 1/3 less,” Hanson recalls.

For ground thawing applications, the Pureheat hydronic surface heater comes standard with 1,000 ft. of hose. Offering a fuel output of 714,000 BTU/hr, the surface heater is capable of thawing up to 18,000 ft² of frozen ground.

The Fargo application represented some of the most extreme conditions for ground thawing. There was nothing to stop the strong winter winds that pushed the frigid temperatures to where exposed skin would be susceptible to frostbite within minutes. With a 5 ft frost depth, this application would have been nearly impossible for air heaters. “We would have had to put up a structure sturdier than tents to withstand the strong winds or just wait for warmer weather,” Hanson explains.

To maximize Pureheat’s effectiveness in this extreme application, workers concentrated on 10 ft x 100 ft sections at a time with each heater. This enabled crews to quickly thaw the ground for digging the 300-ft long footers.

Once in place, the exposed footers could not freeze during the curing period. Crews ran the hoses along the exposed footers to keep them warm in order to properly cure in subzero ambient conditions. Thermocouples were installed at the footers and computers were used to monitor temperatures. According to Hanson, “the footings could not and did not freeze,” with the use of the Pureheat™ hydronic surface heater, and the company has the data to prove it.

Of equal importance to Dunn was heating the area as cost-efficiently as possible. However, the contractor was initially forced into using propane at the onset of the job to run the heaters and for other jobsite needs. The result was a hefty $1000 per day fuel bill.

For added flexibility, Pureheat can be equipped with three different fuel options: propane, diesel or natural gas. As soon as Dunn was able to get the natural gas hookup to the jobsite, crews switched the energy source for the heaters to natural gas. “This move saved us a significant amount of money,” Hanson says.

Dry Pureheat™ Air Heat
Upon closing the office building, Dunn’s crews transitioned the role of the hydronic heaters to provide a clean, dry, safe and warm climate inside. Equipped with HX200 Heat Xchangers™ to convert from liquid to air heat, Pureheat allowed the crews to have consistent, comfortable ambient working conditions where it was needed. Each hydronic heater comes standard with four HX200 exchangers, offering up to 200,000 BTU/hr heating capacity per exchanger (optional HX50 and HX100 Heat Xchangers offering up to 50,000 and 100,000 BTU/hr capacity respectively are also available.)

Unlike direct fired heating units that emit moisture and noxious fumes into the workplace, the self-contained indirect-fired Pureheat™ heater is positioned outside the building to help control moisture inside the building. “We used a piece of plywood in place of one of the glass panes for running the hoses from the heater to the exchangers,” says Hanson. “The heater controlled the moisture and created the perfect drying conditions for installing drywall, taping and painting, and there was no residue left on the concrete.” In addition, the heater may have helped Dunn to earn LEED EQ 3.1 credits by controlling the moisture.

Reliable, consistent heat of the Pureheat™ air heater vs. direct-fired heaters also proved to be a significant benefit for Dunn. The crews weren’t forced to constantly monitor the heaters to see if they were running, so nothing inside the structure would freeze when outside temperatures plummeted below -30° F. “We were able to maintain about 70° F inside temperature, and it was a consistent heat, not cold in one area and hot in another,” Hanson mentions. “I liked how the (Pureheat™) heaters worked, and that we didn’t have to worry about fume, fire and moisture,” like they would have if they used direct-fired heaters.

The Pureheat™ hydronic surface and air heater from Wacker Neuson allowed Dunn to work through the winter months and complete the Microsoft® office building project on schedule. Next time you have to work through extremely cold ambient conditions to keep the project moving, rely on Pureheat™ and Heat Xchangers™ for clean, safe and dry heat.