When it comes to attractive city halls, Auburn, NY, can boast of a Colonial Revival beauty on the National Register of Historic Places. Designed in 1930, the building features a masonry exterior over a steel frame, a columned porch, pediments, pilasters, and fine interior details that create an aura of civic order that officials wanted to preserve.
However, no one wanted to preserve the current heating and cooling system, which featured a wheezy steam boiler and gusty window and ceiling fans that just blew hot air (and papers) around faster. City Manager John Salomone was surprised to learn there was no air conditioning in the building when he arrived a few years ago. Employees sweltered through hot summers, with temperatures topping 95 degrees in some offices.
Taking an innovative approach, City Hall considered its alternatives and elected to install a geothermal heating and cooling system for its efficiency and flexibility. As a result of design studies and careful retrofit, water source heat pumps from McQuay are now installed in city offices, meeting rooms, and hallways. They deliver comfortable, conditioned air while preserving and even enhancing the building’s architectural integrity.
City Hall’s new heating and cooling system had to meet several criteria. It had to be cost-effective, energy efficient, provide a more comfortable working environment, and blend into the landmark building both inside and out. While a gas boiler and central air system was a conventional choice, design engineer John Manning, PE, recommended that the city consider an alternative that might even exceed expectations.
The geoexchange alternative
A geoexchange system reduces energy costs because it draws from the constant temperature of the earth below the frost line - from 40 to 60 degrees F. Geoexchange systems can reduce energy consumption - and corresponding emissions such as carbon dioxide - by over 40 percent compared to conventional systems.
During the winter, water is pumped through underground pipes into the building, where the heat pumps pull heat from the water and distribute warm air to individual rooms or zones, such as a corridor or group of offices. In the summer, the process is reversed, with heated water transferred out of the building into the underground pipes, where it is cooled by the earth. In transitional seasons, heat may be sent to some parts of the building, while other areas require cooling at the same time.
Research seals the deal
Such a system sounded good in theory, but City Hall required more proof that it would meet their requirements. Manning, who heads his own firm, Earth Sensitive Solutions LLC, and Mike Long, grants manager for capital improvement projects for the city, developed a feasibility study of both conventional heating systems and geothermal technology. Their study earned a grant from New York State’s Energy and Research Development Authority (NYSERDA).
The results of the study, presented to the City Council and City Manager, included a comparison of installed cost, operating and maintenance cost, emissions, and aesthetics.
The estimated capital costs for each kind of system were about the same for initial installation - just under $1 million, with the geothermal system costing slightly more.
Operating and maintenance costs
This is where the big difference lay. Annual heating and cooling costs for a geoexchange system were significantly less, with total annual savings estimated at over $19,000.
"These savings, and the competitive initial cost, contradict a common misperception that geoexchange systems are far more expensive than conventional systems and will take a long time to pay back," said Manning. "Another misperception is that geoexchange systems can be installed only in a few geographic areas."
Another difference also caught the attention of the city. The geoexchange system would generate 58 percent less carbon dioxide emissions. So the geoexchange system was not just cheaper to operate, it was also greener.
The city did not want any system to detract from the visual appeal or compromise the historic integrity of City Hall. Here again, the geoexchange system came out ahead. Unlike a chiller, it has no visible external components and generates no external noise.
Impressed with these advantages, Auburn elected to go ahead with a geoexchange system. The City Council approved a million-dollar bond issue to cover the cost of the project.
Installing the geoexchange loop field
A critical factor in the performance and cost-effectiveness of a geoexchange system is getting the right number and depth of pipes in the loop field. "One reason for the misperception about cost is that engineers unfamiliar with geoexchange systems often over-design, putting in more piping capacity than is needed," said Manning.
Engineering tests showed that a series of 35 holes six inches in diameter should be bored 400 feet below the parking lot behind City Hall. Each pipe was connected at the bottom using a "U" bend fitting, so that water could be sent down one pipe, cooled (or heated) by the constant 54-degree temperature in the ground, and come up the other pipe. In addition, a series of horizontal pipes were laid several feet under the surface to connect the vertical pipes. These horizontal pipes run to a valve manifold in the basement of the building. From there, small pipes carry the heated or cooled water to multiple McQuay® water source heat pumps in the offices and other areas of the building.
Blending the old with the new
The entire installation was a study in how to minimize disruption to the original architecture. Contractors were able to actually take advantage of the building’s features to "hide" the geothermal system. For example, the original radiators on the first floor were covered with ornate grillwork. After the radiators were removed, the covers were re-used to house the McQuay heat pumps.
The building’s control system gives occupants more flexibility with temperature control compared to other cooling systems. The set temperature of the control system is 68 degrees F. and City Hall employees can vary this by three degrees up or down. "The McQuay units distributed throughout the building give us an economical system with the added advantage of individual controls," said Salomone. "Our employees like that kind of flexibility."