Case Study: Consulting Engineering

Mountrail-Williams Electric Co-op Headquarters

Mountrail Williams Electric CooperativeWilliston, North Dakota

New Headquarters Provides Expansive Accommodations

The Mountrail-Williams Electric Cooperative (MWEC) headquarters in Williston, North Dakota had outgrown their original building and needed a new space to accommodate more occupants and specialized equipment and technology. Located near the center of western North Dakota oil boom territory, it was important for the MWEC headquarters to remain in its existing location. By redeveloping the existing site and designing a new four-story building, CMTA helped MWEC meet their current needs and prioritize energy efficiency.

The Challenges

  • Select mechanical equipment that would last the life of the building
  • Prioritize energy efficiency and pursue LEED Gold certification within budget
  • Design a 100% electric building with a high-performance envelope and HVAC systems
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We are very pleased with our building and the ease of which the curtainwall construction was brought to the project. Most of all the beauty and energy efficiency it brought to our building — we are so proud! Created with Sketch.

Dale Haugen

MWEC General Manager

The Solutions

The new four-story, 77,773 SF building features a control center, kitchen, combination lunch and gathering room, training rooms, server rooms, meeting rooms, and general office space. The site’s location is adjacent to a natural pond used for stormwater drainage. As an electrical cooperative facility, the design team incorporated the element of a curved electrical conductor as part of the building’s shape. This idea allowed the facility to curve in multiple directions, affording the maximum amount of natural light and connecting it to the adjacent maintenance garage.

MWEC wanted to build a 100% electric building with a high-performance envelope and HVAC systems. After reviewing several different system types, we determined that a geothermal system was the best choice for achieving maximum energy performance. The well field design includes 150 wells drilled to 300 feet deep. An integrated 6-pipe modular geothermal heat recovery type chiller moves thermal energy throughout the building using hot and chilled water piping systems. Additionally, the geothermal loop services water source heat pumps for the server room, computer room, and electrical room cooling, and acts as a backup heat pump for the control room. The hot water loop directly serves perimeter radiant slab floor heating, ceiling panels, and heating coils on Variable Air Volume (VAV) boxes, cabinet unit heaters, and suspended unit heaters. The chilled water loop services the air handling unit chilled water coils.

The modular design allows for improved efficiency and load shifting between heating, cooling, and the well field as the heat sinks. In addition, dedicated server room spaces with redundant independent water-to-air heat pumps allow N-1 redundancy in the event of heat pump failure. Redundancy is crucial in these portions of the building’s infrastructure because it needs to be online 24 hours per day, 365 days per year, to support the Control Center.

The office spaces in the MWEC headquarters building are equipped with VAV boxes for space conditioning control. These controls use occupancy sensors to detect when the spaces are not in use, allowing ventilation air to be turned off. The entire building is fitted with unoccupied set points to maximize energy savings. While the ASHRAE 90.1-2010 baseline system was modeled at 69 EUI, these energy efficient systems have enabled the MWEC headquarters building to operate at 42 EUI based on one year of energy data.

Cost Effectiveness

MWEC advocated for a geothermal-based building and energy-saving provisions to help co-op members reduce utility costs. Before construction, two test bore holes were completed on-site. CMTA performed independent formation thermal response testing on the two wells to determine each well’s expected capacity and to ensure they could use the minimum required number of wells in the system. The mechanical design team worked with the architectural team to improve the building envelope and examine how different decisions impacted the overall energy performance. The team considered three different mechanical systems and their associated life cycle costs during the early pre-design and schematic design phases, comparing their installation, operational, maintenance, and replacement costs.

Through energy modeling, we found that compared to the VAV and distributed heat pump systems, the VRF had the least energy use. The VAV system had the highest energy use, using 7.2% more energy. However, when comparing costs, the 6-pipe VAV design was less expensive than the VRF system’s lifecycle. Overall, the lifecycle cost for the VAV system was 25.8% less than the VRF and distributed heat pump systems.

The Results

Using an integrated design approach by incorporating a 6-pipe heat recovery chiller, and a geothermal well field for transferring energy, these features reduced the building’s energy and environmental impact, aiding Mountrail-Williams Electric Cooperative in meeting and exceeding ASHRAE standards.

CMTA was proud to provide MWEC with a new energy-efficient, high performance headquarters building. By incorporating additional sustainability measures, the facility achieved LEED Gold certification—one of only 12 North Dakota facilities to do so. Not only is the new MWEC headquarters building energy efficient, but it reduces its carbon emissions by 33%.

Mountrail Williams HQ Energy Use