Colorado State Capitol, Denver
Retrofit Team
Energy services company: Opterra Energy Services, Englewood, Colo.
Heat-pump supplier: Ace Mechanical Equipment Inc., Golden, Colo.
Materials
The team designed a hybrid mechanical system that uses a more than 200-ton geothermal-heat-pump system to replace the existing air-handling and supply heating and cooling throughout the building. Another project installed a 10 kW solar PV system to provide electric power to the capitol.
The State Capitol building’s new, state-of-the-art HVAC system includes a total of 9 water-to-air and water-to-water heat-pump units, including three 1.5- to 5-ton horizontal and vertical Tranquility 16 Compact (TC) Series units, four 3- to 5-ton horizontal and vertical Tranquility 30 Two-Stage (TT) Series units and two 3- to 15-ton Tranquility Modular Water to Water (TMW) Series units, all with environmentally sound EarthPure HFC-410A refrigerant. Working within the new mechanical design at-large, these heat pumps contribute to the overall system that provides heating and cooling throughout the building, including in the delivery of air conditioning to the House and Senate Chambers for the first time in the building’s history.
To complete the system, the network of heat pumps is integrated with an open-loop geothermal well system that utilizes water from the Arapahoe Aquifer, located approximately 900-feet below the State Capitol building.
The first phase of the new mechanical system’s installation began in the fall of 2010, when 900-foot supply and return boreholes were drilled into the aquifer. Water (moving through stainless-steel piping set in the boreholes) is designed to be pumped between the building and aquifer at about 350 gallons per minute at maximum flow.
“The ground side of the geothermal system pumps water drawn from the underground aquifer, piping it up through a heat exchanger and then returning it back to the aquifer,” explains Lou Grounds, sales engineer for Ace Mechanical Equipment. “This results in providing consistent indoor temperatures of 65 F through the HVAC system by heating the source water, which is coming from the building, in the winter or cooling it in the summer.”
Once drilling was complete, Opterra Energy Services installed the high-efficiency heat-pump units throughout the State Capitol building, which replaced existing split units and other outdated HVAC equipment. A new pumping system was also installed in the building’s sub-basement area to serve the network of heat pumps.
According to Grounds, the heat-pump units were installed quickly and seamlessly, even when considering some of the retrofit challenges of the project. “When you’re negotiating historic spaces, especially with newer equipment, it’s not always a guarantee that things will go smoothly,” Grounds said. “The units were extremely easy to install, were tested, and were up and running very quickly.”
Jeff Holland, Ace Mechanical Equipment’s owner, adds, “This project is a terrific example of how geothermal heat-pump equipment can help engineers and owners convert a historic, high-profile building with an old, antiquated HVAC system into a modern, high-efficiency, comfortably conditioned building while achieving LEED points in the process.”
Heat-pump manufacturer: ClimateMaster Inc.
The Retrofit
Originally constructed during the late 1800s to early 1900s, the Colorado Capitol Complex, which includes the Governor’s Residence, Colorado Department of Revenue building and the State Capitol building, was slated for a major renovation and restoration by the Colorado Department of Personnel and Administration (DPA) in 2003. Upgrades to its antiquated mechanical system were included.
“Some of the HVAC infrastructure in the complex was more than 80-years old, and the system at-large was generally overdue for an upgrade,” says Lance Shepherd, manager of design and construction programs for DPA’s Office of the State Architect. According to Shepherd, the state also aimed to notably increase the energy efficiency of the complex’s buildings while incorporating the use of renewable-energy solutions.
“Under the Renewable Portfolio Standard, Colorado is requiring the use of 30 percent renewable-energy deployment by 2020,” Shepherd adds. “The mechanical-system upgrade portion of the buildings’ restoration needed to reflect this.”
Shepherd and his team worked with Opterra Energy Services to develop a multiphase program of approximately $30 million in upgrades and improvements. In addition to the HVAC-system updates, this included energy-efficient lighting systems, energy-management systems, water-conservation measures, building-envelope retrofits, removal of outdated equipment and asbestos abatement.
From submittal preparation, review and approval through installation and startup, the project timeline totaled approximately 12 months and continued even during the state’s legislative sessions. In addition to being one of only a few such structures to incorporate geothermal heating and cooling, the State Capitol building was successful in securing LEED-EB certification from the U.S. Green Building Council, Washington, D.C., making it the first LEED-certified state capitol in the country, as well as the first facility to receive the LEED-EB certification at-large
Total project costs were calculated at $6 million, with $4.6 million coming from a Washington-based U.S. Department of Energy grant under the American Recovery and Reinvestment Act. The state funded the remaining $1.4 million through certificates of participation and a lease-purchase agreement with Chevron Energy Solutions, Salt Lake City.
Since coming online in summer 2013, the new geothermal-heat-pump system has generated substantial savings for the state of Colorado. In the first year of operation, $95,000 in utility-bill savings was achieved, and savings are estimated to increase at about 3 percent annually to $165,000 per year by 2029. Payback on the state’s investment in the Colorado Capitol Complex project at-large is estimated to be 19 years with a return on investment for the State Capitol building’s geothermal system calculated at 10 years.