When church officials at Sts. Anne & Joachim Catholic Church in Fargo, ND, added a sanctuary as part of the final phase of a multiphase building plan, they requested an HVAC system that churchgoers would not see, hear, or feel. The building system engineers rose to the challenge and delivered a solution that featured a displacement ventilation system with completely hidden displacement diffusers that are integrated into the architecture with air supplied under the floor by The BlueDuct™ underground ductwork.
“Churches have unique heating and cooling needs,” says Jeremiah Christenson, managing principal and mechanical engineer from Obermiller Nelson Engineering, Inc. (ONE) of Fargo. “The HVAC system needs to respond quickly to accommodate a large congregation of people within a short period of time. To meet this and other requirements, we needed to combine innovative technology without impacting the beauty of the traditional architecture.”
Unique Solution for Unique Needs
Differing from traditional ventilation, displacement ventilation requires multiple strategically located diffusers at floor level to spill the air, at a very low velocity, across the floor. The BlueDuct underground ductwork selected for this project provides the air supply to the diffusers.
Displacement ventilation allows air to stratify rather than mix, resulting in a very efficient system. As the air comes in contact with a heat source, such as people and equipment, the air is warmed and rises. This allows the occupied zone to be conditioned to the proper temperature. The air above the occupied zone can be of a higher temperature without affecting occupant comfort or efficiency.
The BlueDuct’s low-velocity underground air ducts, manufactured by AQC Industries, LLC, allowed for arrangement of displacement diffusers near church occupants and spaced evenly throughout the interior space. AQC Industries worked with ONE to provide proper duct sizing and created CAD drawings to map the ideal duct placement.
The system’s low velocity delivers quiet operation and prevents airflow from being felt when people are sitting in close proximity to the air outlets. Displacement diffusers were ingeniously concealed in the stone pilasters, prayer kneelers, and pews. The return air system was installed in the attic to pull the return air from the top of the 45-ft-tall room. This further reduced any potential noise issues, minimized the effects of stratification, and increased system efficiency.
Putting the System to the Test
The BlueDuct direct-burial underground air ducts were selected for the church because of the product’s durability, inherent insulation value, watertight and airtight properties, and longevity, along with cost-effective and easy installation. Made from advanced HDPE (high-density polyethylene), the products have a low-friction, smooth surface, which also resists mold, mildew, and radon.
They are engineered to exceed load requirements and protect against corrosion. Faster and more affordable to install than other underground ductwork, The BlueDuct does not require added insulation or cement trench structures. In most applications, drain tile is also not required.
“Twelve hundred parishioners and individuals from the community attended the event to showcase the new sanctuary,” says Christenson. “During this event, we closely monitored the temperature of the space. The system adjusted quickly to just above 70°F and maintained a comfortable temperature for 3 hours.”
