Winter residential construction in Norway’s oldest town of Tønsberg is getting a facelift. Building contractor BAS Maskinutleie is bucking the old standby of indirect-fired heaters coupled with small electric heaters for heating structures during the winter while the trades are finishing the job.

Rather than multiple costly heaters, the contractor used one Pureheat hydronic air heater and six HX 60 Heat Xchangers from Wacker Neuson to keep the inside warm and the project on schedule. The end result was a staggering energy savings of more than 50% and a much more efficient heater arrangement.

Tønsberg Mansion
BAS Maskinutleie is one of Oslo, Norway’s largest building contractors. Tackling a range of commercial and residential projects, BAS’ equipment demand is high. So much so, that it formed its own subsidiary rental company to help supply equipment. With a diversified portfolio of work, the construction projects do not stop, even during the cold winter months.

In the past when it came to secondary heating at the job site during winter, BAS would rely on traditional heating sources. A combination of indirect-fired heaters and numerous 10,250 BTU/hr (3 kW/hr) electric heaters, moved from room to room, provided a reprieve from the subfreezing outside temperatures.

During the 2009 season, BAS began construction of a three-story, 26,910 ft² (2,500 m²) mansion in Tønsberg. As the project progressed and winter drew near, BAS crews began working with its internal rental company to prepare for secondary heating needs.  

At about the same time, Wacker Neuson representatives unveiled a more efficient heating method with the rental company. “A similar size house in the neighborhood was previously built, and we knew the type and number of traditional heaters that were required to heat that structure,” says Johnny Valentinsen, sales representative for Wacker Neuson. “We were confident that Pureheat would save BAS money vs. traditional heating.”

To heat the previously construction home, two 98,950 BTU/hr (29 kW/hr) indirect-fired heaters were placed in the stairwells and thirty 10,250 BTU/hr (3 kW/hr) electric heaters were used throughout the rest of the house. Running the two indirect-fired heaters tallied an hourly 1.6 gal (6 l) consumption of diesel, and the cost for electricity required to run the smaller heaters was more than three times higher. The 90-day cost to run the traditional heating system topped $25,000 (150,000 NOK).

Less Costly Pureheat
The simpler Pureheat system proved to be much easier to operate and less costly than traditional heating. One Pureheat unit, positioned outside the house, with its standard 1,000 ft (300 m) of hose connecting to six HX 60 Heat Xchangers is all that it took to heat the mansion that BAS was building. “Rather than finding large holes for ductwork, the crews only had to find space large enough for the small hoses, which made it easier to install,” says Valentinsen.

One heat exchanger was placed in the two stairwells in each of the three levels of the house. The heat emanating from the fluid running through the hoses helped to heat the basement. “We used one day to set up the Pureheat, complete with hoses and heat exchangers,” comments Espen Bråten, site manager for BAS.

A water and glycol solution pumps through Pureheat’s hoses at temperatures up to 180° F (82° C) before reaching the exchanger. Each HX 60 Heat Xchanger then converts this to a clean, dry air heat to warm the inside of the structure. Pureheat offers 860,000 BTU/hr (252 kW/hr) fuel input – 70% more heating capacity than BAS’ traditional heating system – to heat up to 1.2 million ft³ (33,980 m³) spaces.

BAS experimented with Pureheat’s operating temperature in order to heat the house to between 59 and 68° F (15 and 20° C). Initially, “we had a water temperature of approximately 131° F (55° C) during a period when the outside temperature averaged 32° F (0° C),” mentions Bråten.

The crews ran the fans continuously to keep the dry air circulating. Even at this high usage, the per-hour fuel consumption of Pureheat was a paltry 1.5 gal/hr (5.8 l/hr), less than the fuel consumed by the indirect-fired heaters.

As the construction cycle progressed, crews lowered the fluid temperature to 113° F (45° C). Even though outside temperatures during this period dropped to 28° F (-2° C), Pureheat maintained inside target temperatures. “The diesel consumption during this period was approximately 1.1 gal/hr (4 l/hr),” adds Bråten.

At the end of the 90-day period, BAS realized a substantial fuel savings by using Pureheat. This solution enabled BAS to spend only $12,190 ($71,500 NOK) in energy – a 52% energy savings versus the traditional heating system – while offering 70% more heating capacity. For BAS, this represents a return on investment of approximately 225 days, or 2 years of rental.

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