When it comes to attractive city halls, Auburn, New York, can boast of a Colonial Revival beauty on the National Register of Historic Places. Designed in 1930 by the Boston architectural firm Coolidge, Shepley, Bulfinch & Abbott, the building features a masonry exterior over a steel frame, a columned porch, pediments, pilasters and other fine details. Inside, the high ceilings, stenciling, wood paneling, marble accents and ornate City Council chamber modeled on an old Boston courtroom create an aura of civic order that officials wanted to preserve.

The building also featured a wheezy steam boiler and gusty window and ceiling fans that just seemed to blow 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. No one wanted to preserve the current heating and cooling system.

Taking an innovative approach, city hall considered its alternatives and elected to install a geoexchange heating and cooling system for its efficiency and flexibility. Designed by Beardsley Design Associates Architechture, Engineering and Landscape Architechture, P.C., the system could be compatible with the building’s 70-year-old stateliness. As a result of design studies and careful retrofit, water source heat pumps from Daikin – now installed in city offices, meeting rooms and hallways – 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, P.E., recommended that the city consider an alternative that might even exceed expectations.

The geoexchange alternative

Almost without rival for energy efficiency, geoexchange systems reach down into the earth for a natural energy source rather than expending energy with a chiller, cooling tower or boiler. They are ideal for heating and cooling individual spaces, or zones, such as offices and classrooms that require independent heating and cooling.

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 Fahrenheit-for zoned cooling and heating. This approach significantly reduces demand on fossil fuels compared to other HVAC systems. The earth absorbs and stores up to 47 percent of the sun’s energy, according to the Environmental Protection Agency, providing a natural source for delivering constant temperature control above ground. 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.

Geoexchange systems include three main components: an earth connection (such as polyethylene piping) to transfer heat between the water in the pipe and the earth; one or two circulating pumps to move water into and out of the building; and water source heat pumps in each zone area to deliver the required heating and cooling. Both of these components are sized and optimized to significantly reduce energy consumption.

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 SensitiveSolutions, 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:

Installed Costs: 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. The components of the two kinds of systems are listed in Table 1.

Table 1: Comparison of components

Operating and maintenance costs:

This is where the big difference lay. Annual geoexchange heating and cooling costs were significantly less, with total annual savings estimated at over $19,000 (see Table 2). “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 payback,” said Manning. “Another misperception is that geoexchange systems can be installed only in a few geographic areas.”

Emissions: 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, but also greener.

Table 2: Comparison of operating and maintenance costs*

* Operating costs are based on 12.8 cents/kWhr & 85 cents/therm and include only heating & air conditioning costs. Maintenance costs are based on Caneta Research, Inc., Ontario, and ASHRAE studies.