Sustainable Solutions for Historic Buildings: Geothermal Heat Pumps in Heritage PreservationAuthor(s): Thomas Perry and Carl A. JaySource: APT Bulletin, Vol. 40, No. 2 (2009), pp. 21-28Published by: Association for Preservation Technology International (APT)Association for PreservationTechnology International (APT)Stable URL: http://www.jstor.org/stable/40284486Accessed: 22/10/2010 11:32

Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available athttp://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unlessyou have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and youmay use content in the JSTOR archive only for your personal, non-commercial use.

Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained athttp://www.jstor.org/action/showPublisher?publisherCode=aptech.

Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printedpage of such transmission.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

Association for Preservation Technology International (APT) is collaborating with JSTOR to digitize, preserveand extend access to APT Bulletin.

http://www.jstor.org

Sustainable Solutions for Historic Buildings: Geothermal Heat Pumps in Heritage Preservation

THOMAS PERRY AND CARL A. JAY

Ground-source heat pumps can be a

good HVAC renovation option for

historic properties wishing not only to preserve aesthetic features but

also to use green building systems.

Fig. 1 . Section of a standing-column well.

Images by the authors, unless otherwise noted.

Introduction

It has been well established that the built environment has had a profound impact on our natural environment, economy, health, and productivity. With this in mind, owners of historic proper- ties across the country are implementing green building techniques during facility renovations in order to foster more effi- cient energy use and reduce impact on the environment. While geothermal heat-pump technology has been around for decades, owners are now beginning to seriously explore and embrace this high-efficiency heating and cooling sys- tem as a way not only to limit environ- mental impact but also to save money by cutting operational and maintenance costs.

Geothermal heat pumps (GHPs), also known as ground-source heat pumps, are often good options for integration into historic buildings that were not built with today's electromechanical support systems in mind. Also beneficial is the fact that GHPs do not impact the landmark structure negatively either on the exterior or in the interior. While the system is based on the concept of indus- try-proven heat-pump technology, GHPs require careful planning from experi- enced construction and engineering professionals, as well as long-term cost- versus-benefit analysis, before project commencement. The drilling and instal- lation of these wells add initial cost to a project, but energy savings due to sys- tem efficiency will typically pay back the investment within five to twelve years.

This article will explain the installa- tion of GHP systems in the renovation of two significant historic institutions: Trinity Church in the City of Boston and Byerly Hall at Harvard University. It will also explore the lessons learned in each of these projects and the impact these

systems have had on the structure and the environment.

The Environment and Energy Efficiency The most recent report by the United Nations-sponsored Intergovernmental Panel on Climate Change, issued in 2007, concluded that without a dra- matic reduction in human-induced CO2 emissions, climate change may bring "abrupt or irreversible" effects on air, oceans, glaciers, land, coastlines, and both plant and animal species.1 Today, the U.S. is second only to China in CO2 emissions. Alternative energy sources (solar, wind, biofuels) and high-effi- ciency heating and cooling systems are key elements to emissions-reduction plans. In 1993 a landmark technical report by the U.S. Environmental Pro- tection Agency (EPA) on residential space conditioning found that GHPs are the most energy-efficient, environmen- tally clean, and cost-effective space- conditioning system available.2 In the same report the EPA also found that GHP systems have the lowest impact on the environment. Both the U.S. Depart- ment of Energy and the EPA have en- dorsed GHPs, since they use 25 to 50 percent less electricity than conven- tional heating or cooling systems.3 While a higher initial investment is typically required, the investment is paid back through lower energy bills and decreased maintenance cost. Their efficiency, combined with unobtrusive below-ground installation, make geo- thermal well systems ideal candidates for historic-preservation projects.

Geothermal Heat Pumps Defined

There are several basic types of GHP systems, all of which can be categorized

21

22 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 40:2, 2009

Fig. 2. Trinity Church in the City of Boston, 2005. Fig. 3. Section of Trinity Church, showing proposed cooling-tower locations (in gray). Courtesy of Trinity Church in the City of Boston.

as either open-loop or closed-loop sys- tems. An open-loop GHP will pump groundwater from an artesian-type well and circulate it directly through the heat pump. The closed-loop systems consist of a sealed underground piping loop containing water or a glycol mixture that does not come in contact with groundwater. Closed-loop GHPs can have piping configured vertically, hori- zontally, or in a closed coil in a lake or pond. Different systems are better suited to different climates and applica- tions, and choosing the right system is vital for achieving the most favorable life-cycle cost (LCC). This article fo- cuses on standing-column wells (SCWs), which are considered a hybrid of an open- and a closed-loop system.

With a SCW, water is taken from the bottom and returned to the1 top, result- ing in a vertical flow of water and heat exchange. Located near the building, the wells are drilled in bedrock, creating a column of water from groundwater level to the bottom of the bore. Using the earth as a heat source or heat sink, a submersible pump in each SCW draws water from the bottom of the well and delivers it to the building heat pump via an underground piping loop. This pro- cess of extracting water from the bottom of the well and returning it to the top maximizes heat transfer as the water travels the length of the well column. The wells are typically drilled to a depth

of 1,500 feet below the earth's surface, and multiple wells are typically spaced 50 to 75 feet apart. The performance of a SCW depends on well depth, rock thermal/hydraulic conductivity, and bleed rate, if utilized. A bleed system directs return water away from the well, which is designed to allow fresh ground- water to enter the well and bring well- water temperatures back into a normal operating range. Typically, SCWs pro- vide 60 to 75 feet per ton of heat-pump capacity. Therefore, a 1,500 foot well should provide 20 to 25 tons of heat- pump capacity without bleed. Local regulations may not allow bleed; how- ever, if utilized it can improve heating and cooling capacity.

Most historic buildings are located in dense urban areas with little or no sur- rounding open land. SCWs are fre- quently a logical choice for such sites because heat transfer occurs along the 1,500-foot-deep vertical bore hole. By comparison, closed-loop bores are 350 feet deep with closed piping loops grouted in place and typically provide 1.5 to 2.0 tons of heat-pump capacity. Depending on the required system ca- pacity, a closed-loop bore field may require substantial open space due to the number of holes and separation between bore holes, making SCWs a superior choice on a small site. However, not all well drillers will have experience drilling to the depth of a SCW, so the number of

qualified contractors to pick from may be limited. Also, once operational, some SCWs have water-quality issues and high sediment levels that may result in additional maintenance cost such as frequent filter cleaning.

The structure of a SCW begins with drilling a 12-inch bore hole through the soils above bedrock, known as overbur- den, to accommodate the installation of an 8-inch-diameter, 72-inch-thick steel casing that is driven 40 feet into solid bedrock and sealed (Fig. 1). Once the steel casing is installed and grouted in place, a 6-inch bore hole is drilled to approximately 1,500 feet. Once the hole is drilled, multiple sections of 40-foot- long PVC tubing are secured together to form a 1,500 foot induction tube that will act like a straw, drawing water up from the bottom of the well through evenly spaced perforations that are 1- inch in diameter and located in the bot- tom 40-foot section of tubing. At the top of the well casing, two pitless ad- apters are installed on the inside of the steel casing approximately 4 to 5 feet below grade. The pitless adapters allow for ease of setup and removal of the return drop pipe and submersible well pump on the inside of the casing. The submersible pump is stainless steel and is sediment resistant.

GEOTHERMAL HEAT PUMPS IN HERITAGE PRESERVATION 23

Fig. 4. Site plan showing the location of geothermal wells at Trinity Church. Courtesy of Trinity Church in the City of Boston.

Fig. 5. Byerly Hall, Radcliffe Institute for Advanced Study, Harvard Univer-

sity, November 2006.

Life-Cycle Cost of a GHP System

The National Institute of Standards and Technology handbook defines life-cycle cost as "the total discounted dollar cost of owning, operating, maintaining, and disposing of a building or a building system" over the life of the building or system.4 Design professionals and build- ing owners apply the principles of life- cycle cost analysis during the design process as an effective tool in making decisions regarding construction and selection of systems for projects. Life- cycle cost analysis can also be used to evaluate an entire building or a specific building system or component. It must include initial expenses, future ex- penses, and maintenance and repair costs.5

The initial investment for a GHP system should be budgeted and com- pared with other HVAC system costs. The construction manager should con- sider all the costs associated with the installation of each of the systems to be compared, taking into account site work, water mitigation, permitting, schedule, structural supports, and other work items, as well as constructability issues. Once the initial construction cost of the GHP is determined, a life-cycle cost analysis for various heating, venti- lating, and air-conditioning systems should be performed. The project engi- neer can estimate the heating and cool- ing loads using building energy-simula- tion software to determine the annual energy demand for the building. Then, simulated annual performance and

energy consumption for each of the systems can be performed using the computed building loads. In order to compare alternate HVAC systems, a net present value (NPV) for the expected life of the system can then be computed for each system. The NPV of life-cycle cost includes initial capital, annual energy, regular maintenance, and equipment- replacement costs, which are compared along with certain economic assump- tions, such as energy and maintenance- cost escalation and project life. Using this data, the best system for the project can be chosen.

Even though the initial cost of in- stalling a GHP is more than conven- tional systems, the additional cost is usually recovered within five to twelve years due to savings in operating and maintenance costs over other types of HVAC systems, such as air- or water- cooled chillers with hot-water boilers. In addition, on an annual-cost basis, the combined labor and material cost for repair, service, and corrective action are typically lower for GHP systems than for conventional systems. A report on GHPs for the Lincoln Public Schools in Nebraska reported an average total cost of 2.13 cents/ft2 per year, compared to an air-cooled chiller with a gas hot- water boiler at 2.884 cents/ft2 per year, and water-cooled chiller with a gas hot- water boiler at 6.07 cents/ft2 per year.6

The annual heating and cooling hours of the proposed installation must also be calculated, since comparisons will vary greatly depending on the re-

gional electric cost and the availability of gas, oil, and other fuels. In the heat- ing mode it is especially important to evaluate GHP electric costs versus tradi- tional fuel costs. GHP systems installed in regions with low electricity costs may compare more favorably to traditional systems during the heating season. In the cooling mode GHPs are generally more efficient than conventional electrically driven cooling plants. For example the energy consumption for GHP including pumping energy may be approximately 0.65 KW/ton of refrigeration, while the system energy consumption for an air- cooled centrifugal chiller and water- cooled centrifugal chiller may be ap- proximately 1.2 KW/ton and 0.78 KW/ton, respectively. Therefore, build- ings requiring many cooling hours may benefit from greater operating-cost savings with a GHP system.

When calculating life-cycle cost for GHPs, actual electric cost from regional historical data must be obtained to provide meaningful system comparison. Additionally, accurate and realistic heat- pump coefficients of performance and seasonal energy-efficiency ratios must be used. The average well-water tempera- ture in closed-loop systems and SCWs will vary seasonally, thus coefficients of performance and seasonal energy-effi- ciency ratios should not be selected at optimal water temperature. Completing the life-cycle cost analysis at optimum conditions will result in incorrect calcu- lations.

In addition, one must also consider grants, rebates, and tax credits that can

24 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 40:2, 2009

Fig. 6. Section of the standing-column well showing water removal during the drilling process. High-pressure air is pumped down through the drill rods, forcing the water and drill spoils to the surface, which are then removed at grade level.

offset the initial installation cost of GHP systems and significantly affect the life- cycle cost analysis. Federal grants are available for GHP installations through the U.S. Federal Renewable Energy Tax Credit and from the Canadian govern- ment's EcoEnergy for Renewable Power program. Additional rebates and grants vary by state.

The Aesthetic Advantage of GHP Use for Historic Renovations

Installing high-performance systems in historic buildings can pose a variety of challenges for the design and construc- tion team. With the rising cost of en- ergy, many owners of historic buildings are increasingly motivated to replace antiquated mechanical, electrical, and plumbing systems with high-perfor- mance upgrades that will result in

operational and maintenance cost sav- ings. But maintaining the historic feel and fabric of a structure is always a primary focus, and conventional heat- ing and cooling systems can be aestheti- cally objectionable or physically impos- sible to install in structures built prior to the advent of electricity and air- conditioning.

Air-source heating and cooling sys- tems require shaft and ceiling space that is commonly not available in historic buildings. Therefore, designers must opt for HVAC systems that are more adapt- able to old buildings, such as hydronic heating and cooling systems. These types of systems require much less area to deliver the heating and cooling medium to the space. Air handlers, fan coils, or heat pumps can be installed within the area being served and connected to the piping distribution system. However, buildings with vent shafts that may have been used originally for natural ventila- tion can sometimes accommodate the large ductwork necessary for air-source heating and cooling systems.

In addition, exterior HVAC equip- ment is visually intrusive and an unac- ceptable option for preservationists. Therefore, the project team must work together to find alternative systems that maintain the historic integrity of the building. GHPs have minimal architec- tural impact because the heart of the system is located below ground and there is no on-site combustion.

Case Studies

In New England, an area rich with historically significant buildings, GHPs are particularly well-suited to retrofit projects. Two notable institutions in Massachusetts have recently installed GHPs: Trinity Church in the City of Boston, located in the middle of Copley Square in Boston, and Byerly Hall at the Radcliffe Institute for Advanced Study at Harvard University in Cambridge. These two institutions have separate, but similar, needs and site constraints.

Trinity Church in the City of Boston. In 1873 the Boston population, spreading into what is now known as the Back Bay, was forced to stabilize the in-filled ground and build on top of wooden piles to avoid sinking into the marshy wetland.7 In a place where building any

structure was a challenge, architect H. H. Richardson dared to build a massive 9,500-ton church, supported on four elephantine granite pyramids, each of which sits atop 400 wooden piles. Trin- ity Church soon became the center of the burgeoning community, and its de- sign is now considered the inception of Richardson's celebrated Romanesque Revival style (Fig. 2).8 Today Trinity Church is a National Historic Land- mark and one of the country's finest buildings.

When church leaders began planning for a multi-year restoration, renovation, and expansion program in 2005, they had four specific goals in mind: • restore Trinity Church to its original

beauty • expand the church for the benefit of

future generations • update the structure with twenty-

first-century necessities and innova- tions

• keep the church open during con- struction

Some 125 years of use had left the stone facade and the interior artwork, includ- ing murals and stained glass, in need of restoration, and some of the wood pil- ings, integral to the church's structural integrity, were also in need of repair due to fluctuating water tables. In order to undertake such a complex restoration and expansion located on one of the city's dense urban sites, the unusual step of beginning project pre-construction two years prior to groundbreaking was taken. Working in this constricted urban space was made possible through intricate schedule planning and coordi- nated deliveries, disposals, and drilling to ease the impact on the neighborhood. Interior work was planned to allow the church to remain open.

Determining suitable HVAC options for Trinity Church was a considerable challenge for the engineering and design team. After a comprehensive study of the building and grounds, proposed locations for a chilled-water plant were sited on design drawings and presented to the project team for evaluation (Fig. 3). Exterior cooling towers or air-cooled chillers installed on the roofs and within spires of the church were not acceptable from a historic or aesthetic point of view. The only location where this large

GEOTHERMAL HEAT PUMPS IN HERITAGE PRESERVATION 25

equipment could be installed was above the sanctuary, inside the space between the vaulted sanctuary ceiling and the roof spire. Although the proposed loca- tions for the conventional equipment were less than ideal, the project team still provided cost estimates for three types of HVAC systems, including a GHP system that would provide both heating and cooling.

Once the initial construction cost was determined, a life-cycle cost analysis was also performed. The results showed a 10% cost savings over the 20-year life- span of a GHP system compared to the other conventional HVAC systems.9 In addition to cost, other key considera- tions contributed to the final decision to use the GHP system, including aesthet- ics, equipment vibration and noise, and the risk factors associated with installing water piping above the main sanctuary ceiling, which could potentially threaten interior finishes.

GHPs were chosen to provide heating and cooling for the new and renovated spaces. Six self-contained wells were drilled around the church, through layers of soil and bedrock, down 1,500 feet - nearly twice the height of the adjacent 60-story John Hancock Tower, the tallest building in Boston. Drilling 1,500 foot-deep wells in the middle of the city was no easy task. Working just eight feet from the church, construction engineers were able to complete the project without damaging the stone or foundation (Fig. 4).

Byerly Hall at Harvard University. Rad- cliffe College (now part of Harvard University) was founded in 1879 as the Society for the Collegiate Instruction of Woman, to educate women with Har- vard-quality classes.10 As enrollment grew, Radcliffe began to buy and erect buildings on Appian Way, on what became known as Radcliffe Yard.11 In 1893 Radcliffe became a self-governing college under Harvard University's stewardship.12 In 1930 the General Education Board awarded Radcliffe College $500,000 for the construction and equipping of laboratories for the physical sciences. The new science building, designed by Coolidge and Carlson of Boston, was begun in 1931 and completed by the time the classes started in September 1932. 13 Named

after William Elwood Byerly, a former professor of mathematics at Harvard and an early supporter of the college, it was one of the last buildings to enclose Radcliffe Yard in the western quadrant of the Harvard campus (Fig. 5).14

In 2007 the Radcliffe Institute for Advanced Study at Harvard University commissioned a team to rehabilitate the historic neo-Georgian facade of Byerly Hall, renovate the interior to meet twenty-first-century needs, and install five SCWs in Radcliffe Yard to provide heating and cooling for the classroom building, which would now house the Radcliffe Fellowship Program. The rec- tangular wings of the building contain offices and studios for the fellows and fellowship administration, with social and community spaces at the connector on each floor to help foster interac- tions.15

Harvard University's commitment to reducing its carbon footprint has engen- dered a campus-wide focus on promot- ing sustainability in all areas of univer- sity operations. In the case of Byerly Hall, it was determined that in order to meet the university's goals for sustain- ability, the building would use geother- mal-well technology for its heating and cooling needs. The new GHP system required five SCWs, each 1,500 feet deep, and a mechanical room built to house the heat pump. Once installed, the system was set up to ensure optimized energy performance as part of the pro- ject's LEED goals.

Site Activities during Well Drilling and Installation

The drilling operation for GHPs can at times overtake a tight job site, since the wells are typically located along the perimeter of the building and dewater- ing equipment needs substantial area for proper functioning: a typical setup includes generators; discharge, or frac, tanks; and tubing. An area for tempo- rary storage of drill spoils and sediment may be needed, so the spoils can dry out and be trucked off-site later. In addition, this area must be surrounded by hay bales to prevent unwanted water runoff.

During the pre-construction and planning stage of a project, a detailed site-logistics plan must be prepared,

Fig. 7. Section showing excess water volume at well 5 at Byerly Hall. The image on the left shows the drilling process proceeding as planned to the point of contact with the large fissure. The image on the right shows the slowing of the drilling process, due to an exces- sive volume of water coming from the fissure.

specifying site activities, equipment, en- vironmental protection, fencing, pedes- trian traffic, etc. On many projects drill- ing is scheduled to take place before main construction activities, but it can also be phased to allow building access. The latter was the case for Trinity Church, where church services and meetings could not be disrupted because of drilling noise or vibrations.

Located in an academic and residen- tial area, Byerly Hall's tight site was a challenge for project planning. Because the space requirements for a large drill- ing operation are considerable, work had to be completed on the wells and drilling equipment had to be moved out before work could begin on the renova- tion of the structure. Two large drill rigs were used during the drilling process in order to meet the project schedule, which was constrained by neighborhood ordi- nances allowing work between 7:00 a.m. and 7:00 p.m., complicating the already tight schedule.

Water-removal process. Handling water and drill spoils at grade level can be one of the biggest challenges and

26 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 40:2, 2009

Fig. 8. Diagram showing sediment production in the Radcliffe Gymnasium SCWs (at left) during Byerly Hall well drilling (at right). As indicated by the arrows, water removed by the drill rig at Byerly Hall upset groundwater characteristics at the gymnasium.

largest costs when drilling a SCW. During the drilling process, air is pumped down the center of the drill rods through the drill head at high pressure to blow the water and drilling spoils from the bore, thereby allowing the drill head to operate efficiently (Fig. 6). The volume of water evacuated from the hole is a function of how much water the well can produce. The method for handling the water that is blown from the well can vary greatly according to the job-site conditions; regulations in urban areas will require more complex drill-water management. The Byerly Hall project is an example of an urban site requiring the handling and filtering of large amounts of water, thus requiring a substantial amount of equipment on site, which included two diesel trucks with drill rigs, hundreds of feet of hoses, a 40-cubic-foot lined dumpster for heavy sediment, two 10,000-galloon water-holding tanks for sediment separation, and a triple-filtra- tion station.

Drilling operations onsite. Water and spoils are collected at the top of the drill head and piped with hoses over to an open tank (typically a dumpster lined with plastic). In order to manage the high pressure of discharged water and spoils, a collection device called a cy- clone is used to control spray and direct

the drilling debris into the open tank. Several discharge tanks, or frac tanks, are equipped with a series of baffles that allow the water and sediment to sepa- rate. At Byerly Hall two large side-by- side frac tanks, 20,000 gallons each, were operated in series due to the large quantities of water encountered during the drilling process. The final outlet on the last tank was then connected to a triple-filtration station comprised of 50-, 30-, and 10-micron reusable bag cartridge filters and drained into a nearby catch basin.

The Massachusetts Water Resource Authority required the Byerly Hall proj- ect to test water leaving the final filtra- tion station for turbidity before it was piped to the catch basin, since the dis- charge water will eventually end up at the authority's Deer Island sewage- treatment plant located in Boston Har- bor. For SCW systems, federal and state regulations involve permitting of water withdrawal and responsible return of the water to the earth. Other regulations may apply to excessive withdrawal, return to navigable streams or rivers, and other activities that may impact the water supply or quality. It is recom- mended that state and local agencies be contacted early in the design process to determine what permitting arrangements must be made.

Underground piping. Supply and re- turn high-density polyethylene (HDPE) piping was installed approximately 5 feet below grade to carry water from the well to the heat pumps located in the building. Pipe joints are butt or socket heat fused by a method approved by the pipe manufacturer and the Inter- national Ground Source Heat Pump Association. Rigid insulation is installed underground between the supply and return piping to prevent heat transfer.

Noise mitigation. Project drill sites that are located near occupied buildings may need to be evaluated for noise pollution from the drilling equipment. During the Byerly Hall project a 30-foot-high wall of sound blankets was erected to atten- uate the noise reaching the nearby Education Department Office. On the Trinity Church project there were initial concerns regarding vibration and noise in the midst of Copley Square. The team installed vibration monitors and

determined that the machinery operat- ing the drills emitted decibel levels equivalent to those of a bus accelerat- ing, a familiar sound in that environ- ment. Nevertheless, noise-reducing wooden structures were erected, and crews worked overtime to complete the drilling as quickly as possible. Given the project team's concerns with disrupting the community, the bulk of the noise- generating activity was scheduled to occur during January and February, when there was the least amount of activity in the square, and before the start of the Lenten season, when the church's services would be in highest demand.

Concerns about Geothermal Well

Operation

With all mechanical, engineering, and plumbing systems, careful planning and research of various options can help determine whether a system is right for a project. With GHPs it is equally im- portant to weigh the system's pros and cons carefully. During peak heat-rejec- tion or extraction periods, the well- water temperature can rise too high or fall too low, which can negatively im- pact heating and cooling performance. In these high-load periods, some SCW designs incorporate a bleed system that directs return water out of the well in- stead of recirculating the water, a pro- cess that allows fresh groundwater to flow back into the well. This process cools down the well water in the sum- mer and warms it in the winter, thus restoring the water temperature to a normal operating range and improving system performance. It is important to note that state or local groundwater regulations may prohibit bleeding. The projects described above currently operate without bleed.

In addition, industry experts report that the earth temperature around SCW systems does fluctuate on a seasonal basis, typically within 40 to 50 feet from the borehole column. Field tests per- formed over the course of ten years have shown no annual change in the mean earth temperature in properly designed SCW systems. Proper design must recog- nize geologic thermal characteristics, relative heating and cooling loads, and adequate spacing of multiple SCWs.

GEOTHERMAL HEAT PUMPS IN HERITAGE PRESERVATION 27

Typically SCWs are spaced 50 to 75 feet apart, because closer spacing can reduce well efficiency due to thermal interfer- ence.

Post-Construction Well Maintenance

Since the only visible indicator from ground level of the SCW is the manhole cover, building owners can inadver- tently fall into the trap of a "out-of- sight, out-of-mind" attitude when it comes to well maintenance. However, it is recommended that the first inspection of the wells occur one year from initial start-up and that a schedule for subse- quent maintenance inspections be de- cided upon by the well-service contrac- tor and the building owner. A service contract should include removal and inspection of well pumps; removal, inspection, and cleaning of the return drop pipe; inspection of well wiring for nicks and frays (doubled jacketed wire is recommended); and testing of well water every 18 months to 2 years. Weekly inspection of the GHP system should include, but not be limited to, cleaning of the well-water filters; inspec- tion of well-pump variable-frequency drives, heat pumps, and associated circulation pumps; and readings at gauges and thermometers.

SCW systems should be maintained in a sterile state at all times. Any open well system, whether used as a heat pump or only domestic use, should be free of harmful bacteria and should be checked periodically. Iron bacterium, which is not harmful to humans, causes red-brown deposits in pipes that, if not controlled, can eventually lead to oc- cluded pipes. Industry manufacturers claim that GHP heat exchangers are not affected during air-conditioning periods, as they are manufactured of copper- nickel alloy. However, control of such bacteria is still recommended.

Lessons Learned

Since geothermal heating and cooling is a relatively new technology, unexpected conditions often arise during installa- tion. Several notable challenges arose on the Byerly Hall project during the drilling process. The project schedule was to drill five 1,500-foot-deep wells in two months. Due to the noise of

drilling operations, the work was sched- uled to be completed prior to the com- mencement of school in early Septem- ber. The project was progressing as scheduled until the last of the five wells began producing water at a volume that stopped the drilling process. During the drilling of the last well, water volumes in excess of 350 gallons per minute exceeded the drilling machinery's capac- ity to evacuate water fast enough to continue drilling, and the well had to be abandoned at a depth of 650 feet (Fig. 7).

At a project-team meeting several options were discussed, including the drilling of a new well. A new well was not a favorable choice, due to the added cost to the project and extended sched- ule to complete the work. The design team came up with an option to use well five as a discharge/dispersion well: this would be used during adverse load conditions when well-water temperature in wells one through four dropped below 45°F in winter and rose above 85°F in summer. Instead of recirculating the water into these wells, water would be diverted to well five, allowing local groundwater to flow back into wells one, two, three or four, thereby cooling or heating the well water to an accept- able range for heat-pump performance. The building has now completed one full heating- and cooling-season without having to use well five.

Another problem was encountered at Radcliffe Yard during drilling. The yard (approximately 20,000 square feet of green space and pathways) contained various utilities, such as steam-distribu- tion pipes, high- and low-voltage electri- cal lines, and telephone/data lines, as well as two existing geothermal wells servicing nearby Radcliffe Gymnasium, which had to be located and coordi- nated with the new SCW locations prior to the arrival of the construction team.

Several weeks into the drilling pro- cess, it was determined that an addi- tional drill rig was needed to meet the scheduled completion date. The two well rigs operating simultaneously were pumping a high volume of water from the ground below. Meanwhile the facili- ties department in charge of the Rad- cliffe Gymnasium notified the construc- tion team that heavy sediment was found in the gym well-water filters,

consequently clogging the system and upsetting water flow (Fig. 8). Eventually it was decided to shut down the gymna- sium's GHP system until the drilling process in the Radcliffe Yard was com- plete. Fortunately, the building was only lightly occupied due to summer vaca- tion, and temporary cooling for a small server room was installed for the interim period. The exact fissure and aquifer formations connecting SCWs deep below the surface are impossible to predict, but future project planning should include the close monitoring of all well types located in proximity to a drilling operation.

The Future of Geothermal Wells for Historic Structures

Trinity Church and Byerly Hall both provide evidence that GHP systems are often a good fit for historic preservation projects, due to their high efficiency and low aesthetic impact. For the two insti- tutional owners, the conversion to a GHP heating and cooling system has been a positive one. Trinity Church's geothermal system has delivered signifi- cant benefits due to its economical and nearly invisible operation. The GHP system at Byerly Hall has contributed to Harvard University's environmental goals and the project's LEED certifica- tion. GHP systems are a viable alterna- tive to conventional HVAC systems and can be a good solution for both energy- use concerns and historic preservation goals.

THOMAS PERRY, LEED AP, managing direc- tor of Engineering Services Division at Shaw- mut Design and Construction, has more than 30 years of construction experience, including 20 years of HVAC design experience. He holds a BS in mechanical engineering from Northeast- ern University. He can be reached at tperry® shawmut.com.

CARL A. JAY, director of historic preservation at Shawmut Design and Construction, has worked on many prominent restoration pro- jects including African Meeting House in Boston, Touro Synagogue, and several build- ings at Harvard University. He has a degree in wood science and technology from the Univer- sity of Massachusetts. He can be reached at caj@shawmut.com.

Acknowledgements

The authors wish to recognize the following Shawmut employees who have generously shared

28 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 40:2, 2009

their time and experience: Jennifer Bentley and Liz Jennings. The project teams for both case studies included Shawmut Design and Construc- tion as construction manager, Goody Clancy as architect, and Cosentini Associates as mechani- cal, electrical, and plumbing engineers.

Notes

1. Intergovernmental Panel on Climate Change, Climate Change 2007: Synthesis Report. Con- tribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergov- ernmental Panel on Climate Change, ed. R. K Pachauri and A. Reisinger (Geneva, Switzer- land: IPCC, 2007), 30.

2. Environmental Protection Agency "Space Conditioning: The Next Frontier," EPA430-R- 93-004, April 1993.

3. National Renewable Energy Laboratory, report for the U.S. Department of Energy, "Geothermal Heat Pumps," Energy Efficiency and Renewable Energy Clearinghouse, DOE/ GO-10098-652, FS 105, September 1998. Available at http://www.nrel.gov/docs/legosti/ fy98/24782.pdf.

4. State of Alaska, Dept. of Education and Early Development, Life Cycle Cost Analysis Handbook (Juneau: U.S. Government Printing Office, 1999), 2.

5. Ibid.

6. Michaela A. Martin, David J. Durfee, and Patrick J. Hughes, "Comparing Maintenance Costs of Geothermal Heat Pump Systems with Other HVAC Systems in Lincoln Public Schools: Repair, Service, and Corrective Ac- tions," prepared for the U.S. Department of Energy, Oak Ridge National Laboratory, Oak Ridge, Tenn., Contract DE-AC05960R22464, and presented at the 1999 ASHRAE Annual Meeting, Seattle, Washington: June 19-23, 1999.

7. Theodore E. Stebbins Jr., "Richardson and Trinity Church: The Evolution of a Building," Journal of the Society of Architectural Histori- ans 27 (1968): 281,283-284 .

8. Ann Jensen Adams, "The Birth of a Style: Henry Hobson Richardson and the Competi- tion Drawings for Trinity Church, Boston," The Art Bulletin 62 (Sept. 1980): 409.

9. Shawmut Design and Construction, Life Cycle Cost Analysis for Trinity Church, 2002.

10. Crimson Key Society, Guidebook to Har- vard University (Cambridge: The Belknap Press of Harvard Univ., 1989), 19.

11. Ibid.

12. Ibid, 20.

13. Ibid, 25.

14. See www.news.harvard.edu/gazette/2008/ 09.18/09-byerly.html.

15. The work on the exterior of the building included the restoration of eight chimneys, repointing of the exterior brick, replacement of the granite and all windows with new sashes complete with historic glass, and repair of the slate roofing over about half the building. The new external features, such as the south exte- rior ramp with a glass railing, were designed to have a minimal visual impact but were made distinguishable from the 1930s-era building fabric. The project also included construction.