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Energy Efficiency

More architects and designers are turning to geothermal heating and cooling systems for historic buildings, as well as for new construction.

By Martha McDonald

Geothermal systems are being used more often these days, as clients and architects discover the advantages. They use less energy than conventional HVAC systems, so they are friendly to the earth as well as to the pocketbook, providing energy savings over the years. At the same time, geothermal systems are often easier to install into historic buildings because they have less of an impact on the structure.

Notable restorations such as Trinity Church in Boston and a Motherhouse in Monroe, MI, have incorporated geothermal heating and cooling systems and are giving them good grades. Unity Temple in Oak Park, IL, is gearing up to start installation of its geothermal system. At the same time, new construction projects such as the K.C. Irving Environmental Science Centre at Acadia University in Nova Scotia, Canada, are installing geothermal from the beginning.

Geothermal systems rely on the earth's natural thermal energy, a renewable resource. At approximately six ft. below the earth's surface, the temperature of the ground and groundwater remains stable at approximately 55 deg. F. Heat pumps draw heat from the earth to provide heat in the winter; in the summer, they draw excess heat from the building and transfer it back to the earth.

There are two basic types of geothermal heat systems: closed-loop and open-loop. The open-loop type uses groundwater from wells or surface water from lakes or ponds. The closed-loop type uses a plastic piping network installed either (1) vertically in drilled boreholes or (2) horizontally in trenches or excavations or (3) submerged in lakes or ponds. Vertical systems go deeper and are used on urban sites where land is limited. In horizontal systems, the pipes are closer to the surface (usually 4 to 6 ft.).

While the major advantage is significant energy and money savings over time, other advantages often cited include the fact that geothermal systems require considerably less equipment attached to the building, are quiet and require very little maintenance. The primary disadvantage is higher initial installation costs, but proponents are quick to point out that the energy savings over time more than compensates for this. Another problem is a lack of awareness among the population in general and in some cases, it's still hard to find an installer who's knowledgeable about geothermal.

Statistics from the Geo-Heat Center at The Oregon Institute of Technology, Klamath Falls, OR, show that sales of geothermal systems are growing 10% to 20% a year, according to Andrew Chiasson, research engineer. "About 40,000 units are sold each year," he says. "The technology started in the residential market, but it has slowed down there. Schools and office buildings, especially schools, are the fastest growing segments now. Geothermal has gotten very popular for historic buildings because there is no visible equipment. The pipes are buried underground and the heat pumps can be hidden in closets. There is no outdoor equipment, which means low maintenance and no noise."

He estimates savings in kilowatt hours can amount to 50% - 75% for heating and 30% for cooling. "The translation into dollars is a little different because heating uses fossil fuel," Chiasson says. "One of the barriers is finding contractors who can do the work. There are more people trained in it every year, but that is still a barrier. The cost of installation is usually higher because of the piping, but the payback is usually 5 to 10 years."

The Geothermal Heat Pump Consortium in Washington, DC, says there are more than one million installations in place in the U.S., saving 14 million barrels of crude oil a year. This website points out that the technology has been around for years, but recent improvements in materials and installations, efficiencies of compressors, pumps and other equipment have made it more appealing. This group estimates that sales are growing 20% a year and that geothermal lowers utility bills by 25% to 75%, while producing fewer greenhouse emissions. "It is especially good for historic buildings because there is very little impact to the building," according to this web site. (

Recently renovated by Boston-based Goody Clancy & Associates, Boston's 1877 Trinity Church decided to use a very deep vertical system. Six holes were drilled 1,500 ft. into the bedrock., 45 to 75 ft. apart on the southern and western sides of the building. The system includes 13 heat pumps housed in an underground mechanical room and is designed to heat and cool the 14,000 sq.ft. renovated space below the sanctuary as well as the adjoining 15,000-sq.ft. parish house. The cost of installation was approximately $800,000, plus $400,000 for the pumps and piping.

"We used a standing-column well design," says Stefan Knust, AIA, Associate, Goody Clancy. "This type of system is used where you have sound bedrock, which serves as the container for the 1,500-ft.-high column of water. By inserting a narrower 'straw,' the water is drawn up from the bottom and moves through the heat-pumps within the building before returning to the top of the well. Overall, the water circulates along a 3,000-ft. path, moving slowly, gathering and delivering heat along the way. The quantity of wells was based on how much heating and cooling was needed, and the system's modular design allows for both demands to be met at the same time. The depth of the wells is almost twice the height of the nearby 793-ft. Hancock Building."

"We did look at other options, but this was the clear winner," Knust adds. "Geothermal systems are almost a no-brainer for historic buildings because they don't touch the building or introduce noise or vibrations. In this project, the estimated cost of putting in a conventional system was very high, comparable to the cost of installing the geothermal system. Plus it uses 40% less energy than a conventional system."

Trinity Church spokesperson Patricia Hurley says that the church is very pleased with the geothermal system. "It was a significant decision and we are particularly pleased with how invisible it is," she says. "We also felt very strongly that we wanted to work with the earth rather than using the resources of the earth. We have only been using it for a year, but our life-cycle analysis showed us it would pay off over time both ecologically and economically." Another high profile restoration that made the decision to use a geothermal system is Frank Lloyd Wright's Unity Temple in Oak Park, IL. Designed in 1905 and opened in 1909, the Prairie-style building is undergoing a multi- million-dollar restoration that includes the addition of a geothermal system. Plans call for 26 wells to be drilled into the bedrock around the perimeter of the building, each 300 to 400 ft. deep. The system will provide both heating and cooling and will be supplemented by a high-efficiency boiler system. Existing ductwork and venting included in Wright's original design will be used.

The new system is expected to cost $2 to $2.5 million, about 40% to 50% higher than installing a conventional HVAC system, according to Keith Bringe, executive director of the Unity Temple Restoration Foundation. He expects for it to pay for itself in eight to nine years. "Our incremental payback might be much sooner than anticipated because of the rising cost of fossil fuels," he adds.

"This is a win-win situation," says Bringe. "The building will be both historic and green. We think this will be an important model for the state and for other historic buildings throughout the country." He added that Frank Lloyd Wright designed one of the first forced-air electric system for the building, but it never worked. "Now we will be able to go back to that system and integrate parts of it into the new geothermal system."

Meanwhile in Monroe, MI, the Sisters, Servants of the Immaculate Heart of Mary (IHM) incorporated a very large geothermal system when they renovated their Motherhouse in 2003 because they wanted a system that was earth friendly. Built in 1932, the 376,000-sq.ft. building was converted into a retirement home for 240 sisters. It also serves as headquarters for the IHM congregation. Because of the harsh winters, they needed a system that provided an 80/20 heating-to-cooling ratio.

It took about eight months to install the Motherhouse's closed-loop system, which includes 232 boreholes, each 450-ft. deep, connected by 47 miles of pipe. There are also 466 fan coil units in the house, along with 10 miles of piping and 6 miles of ductwork, also in the Motherhouse building.

The initial installation of the outside portion of the project cost about $1 million, says Danielle Conroyd, project director, Sisters, Servants of the Immaculate Heart of Mary. "We think the payback on the initial investment will be six to seven years. It has already significantly reduced our heating and cooling costs. We found that we reduced gas consumption 58% and water consumption by 49% (from the graywater system) in the first year, for a savings of $187,000," she says. "A large portion of that was from the geothermal system."

The biggest challenge was drilling the holes, Conroyd explains. "The engineers estimated it would take nine to ten hours for each hole, but it actually took 18 hours. Initially we had four drill rigs on the property and about a million gallons of water was displaced every day. We created ponds to store the water and after the sediment had settled out, we pumped it into the local storm system.

"Sometimes the air pressure from the drilling would push the ground water into previously drilled holes and that would push the pipes right out of the ground. With all of these rigs working at the same time, there was a tremendous amount of air pressure going into the ground and water being displaced. Because of these problems, the installers decided to pull two of the rigs off the site and keep two going."

She also stresses that the boreholes are holes, not wells. "We were not tapping ground water to use for our system," say Conroyd. "It's an important distinction. We would have needed a permit for wells."

The system is a huge success, providing not only energy savings, but also comfortable heating and cooling. "Every sister has a thermostat in her room," says Conroyd. "It's a very quiet system. It's an alternative that is benign and is very comfortable. You don't have to sacrifice any comforts. The sisters love it." She also points out that the system is invisible. The geofield in hidden under a parking lot and the front lawn and the manifold vault is set into the ground.

Ronald Staley, vice president of The Christman Company, the construction manager for the Motherhouse project, points out that geothermal systems must be incorporated into a project during the early planning stages. "From a construction planning and implementation standpoint, the logistics of laying out the geothermal field must be considered early in the project planning and design," he says. "Water and slurry retention ponds, impact to historic trees and working around known or unknown underground utilities can have a significant impact on the cost and ability to install a suitable system within the project site."

Geothermal systems are also appearing in new construction. Completed in 2002, the 65,000-sq.ft. K.C. Irving Environmental Science Centre and Harriet Irving Botanical Gardens at Acadia University in Wolfville, Nova Scotia, Canada incorporates a geothermal system for cooling only. There is a steam generation plant that heats all of the buildings on campus.

This system takes advantage of a large, nearby aquifer. Water is drawn from the aquifer, pumped up a hill, sent through the heat exchangers and is then gravity-fed into a recharge well and slowly drained back into the aquifer. "The temperature difference between the supply water and the refill water is only a few degrees, which is very important," says Preston J. Gumberich, AIA, associate partner, Robert A.M. Stern Architects. "The initial motivation for this system came from our client, the Irving family. They are very interested in environmental issues and since this is an environmental science center, they wanted to incorporate the latest technology to create a more sustainable building."

"We are very happy with the system," states Peter Romkey, director of the science center and botanical gardens. "We are an environmental science center, so it made sense from the perspective of savings in electricity and from the perspective of conserving the earth's resources. We needed a robust cooling system for the research environments. The cost to cool the research facility alone using conventional system would have been significant, and you would have had condensers running outside of the buildings."

He adds that other buildings on campus are investigating geothermal technology for both heating and cooling and the community is watching to see how it affects the aquifer. Romkey also cites low maintenance as an advantage. "We think it will be 25 years before we have to replace or service the pump," says Romkey. "It's a very robust, reliable system for cooling."  



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