Modernizing History

Geothermal systems bring two Chicago landmarks up to date.

By Jennifer Strawn

Two historic Frank Lloyd Wright buildings near Chicago—the Unity Temple and the Emil Bach House— recently underwent significant restorations to return them to their former glory.

Wright offered to design the Unity Temple in 1905 after lightning struck the spire of the wood-framed Unitarian Church, causing it to burn to the ground. Wright’s version was a one-of-a-kind church at the time with no steeple and no front entrance. It was also one of the first public buildings to use concrete in the exterior’s design.

Emil Bach, the president of Chicago’s Bach Brick Co., commissioned Wright to build his home in 1915. The compact 1600-square-foot, two-story home had three small bedrooms and a sundeck on the second floor with stunning views of Lake Michigan.

The recent restorations to both structures matched the materials and finishes as closely as possible to Wright’s original designs, but with a few notable exceptions.

One of the biggest is they are now heated and cooled by modern geothermal systems.

Gunny Harboe, owner of Harboe Architects in Chicago and lead architect for the projects, often recommends geothermal to clients with historic buildings because the systems stay hidden from view.

“When you have to find a place to put these big ugly air conditioning condensers, it’s a problem,” he says. “As an architect, I’m worried about the historic fabric of the building. Geothermal systems don’t affect your visual ability to experience the house or building as it was originally intended to be.”

They also offer humidity control, which is critical in old, historical buildings. In fact, Mark Nussbaum, PE, with Architectural Consulting Engineers in Oak Park, Illinois, and the engineer for both projects, believes interior humidity played a role in some of the damage to Unity Temple’s exterior.

“(Geothermal systems are) able to simultaneously control temperature and humidity,” Nussbaum says. “You get that for free, where every other technology requires expending new energy to control humidity.”

Owners of historic buildings are often set up as not-forprofit organizations, which can apply for grants for geothermal and other energy-efficient upgrades. These can be beneficial as they can stabilize energy bills and make it easier to manage a limited budget.

But while it might be easy to convince these clients to choose geothermal, no project is without its challenges. That’s especially true when the job site is an historic landmark.

The Emil Bach House

The Bach House, which was designated a Chicago Landmark in 1977 and placed on the U.S. Register of Historic Places in 1979, is now a short-term vacation rental owned by Tawani Enterprises Inc.

The interior underwent a major restoration by the previous owner and Tawani Enterprises hired Harboe Architects to restore the exterior and add the geothermal system. In previous renovations, the sundeck was converted to a living space, but the restoration removed these changes—so the house regained its original design integrity. The project also included the restoration of exterior masonry, concrete, and stucco.

Sub-Surface Geothermal Inc. in McHenry, Illinois, drilled and installed the geothermal loops for the system. They drilled two 500-foot-deep boreholes in the home’s backyard and installed standard 1-inch U-bend loops grouted with a bentonite-based thermal grout.

“Geothermal systems don’t affect your visual ability to experience the house or building as it was originally intended to be.”

The project went seamlessly in Nussbaum’s opinion, with only a few challenges.

“Drilling conditions here in Chicago are pretty good,” he says. “We have a standard 75 feet of overburden, then you get into the soft shale and limestone. Then it gets harder down about 150 feet. They’re able to get pretty easy drilling for the first half, then a little harder rock the second half.”

The site’s elevation caused the only challenge on the project, which was otherwise similar to most typical residential projects. The house was elevated about 8 feet off the primary street and about 2 feet off an alley.

“There was a large side yard associated with the site but they didn’t want to use that for the loop field,” Nussbaum says. “When I first saw the site, I thought this would be simple. But we ended up having to work around existing structures and some tight borders.”

The equipment had to be brought up ramps from the alley, and—luckily—there was enough space in the backyard to accommodate the two boreholes needed to meet the home’s heating and cooling demands.

The Unity Temple

The project for the 16,000-square-foot Unity Temple in Oak Park, just outside of Chicago, wasn’t as simple.

The Temple—which is home to a Unitarian Universalist Church—was designated a National Historic Landmark in 1970, and the U.S. Department of the Interior authorized its nomination, along with 10 other Frank Lloyd Wright buildings, for listing as a UNESCO World Heritage Site in 2014.

Like the Bach House, the loop field was located in a confined space—this time in the front yard of the Temple, which is only about the width of the building plus 20 feet.

To complicate matters, the building has irregular load patterns. It could be empty; it could be at capacity for three events in a row; or it could be somewhere in between.

Nussbaum completed an initial feasibility study in 2004 to prove air conditioning could be added to the building and geothermal would work.

When funding came through for the geothermal project several years later, he began from scratch on the design. He first modeled the system with nine boreholes drilled to 500 feet and traditional U-bends.

“The conventional boreholes were okay, but we were a little marginal for large events,” he says. “So, we remodeled it using (HDPX technology from) Rygan.”

Nussbaum describes the product like a “standing column system.” An outer casing is put down the borehole and then an inner pipe is dropped in. Water flows down the inner pipe and around the annulus in between the outer and inner pipe and back up the hole.

Lane Lawless, now the operations and project manager for Rygan Corp. in Tulsa, Oklahoma, developed the technology with Dr. Mike Fraim, who now serves as Rygan’s chief scientist. They could tell neither closed-loop or open-loop geothermal systems quite fit the bill.

Open-loop systems—although most efficient—required ongoing well maintenance the company was unwilling to do. Closed-loop systems require less maintenance, but there was not enough space for the number of boreholes needed.

“Most of these sites are on leased space,” Lawless says. “If you go a fingernail beyond a property line, they want more money.”

Polyethylene pipe, Lawless and Fraim believed, caused closed-loop systems to be less efficient.

“It’s not meant to be a good heat exchanger,” Lawless is of the opinion. “It has poor heat conductivity and high thermal memory—the opposite of what you want in heat exchange— and that’s the reason you don’t see plastic condenser tubes.”

They set out to create a better closed-loop system with low thermal memory and better conductivity, but one that was still strong, sturdy, and would resist the corrosive effects of direct burial over the decades.

“The only material that had a track record for doing that in really high stress direct burial applications was composite fiberglass pipe, which is the essence of what our pipe is,” Lawless says. “We can specifically engineer the composite resin that goes around the glass fibers to have low thermal resistance. We have a material and a vessel that’s, at minimum, triple the strength of poly pipe.”

The pipe has an epoxy joint every 20 feet and is grouted with a high density carbon backfill to get the best thermal performance.

With low thermal resistance and almost no thermal memory, the company claims to get 100% better performance per foot of borehole.

“Theoretically, if you need 10 boreholes drilled to 500 feet, you can get by on five holes drilled to the same depth,” Nussbaum figures. “We went ahead and put in nine holes, which gives us a lot of buffer. If the saying is true, it gives us a lot of fat.”

Great Lakes Geothermal in West Chicago, Illinois, completed the drilling and the installation of the HDPX. Eight holes went smoothly, but the weight of the grout caused the pipe to collapse downhole on the ninth hole.

“The piping has a pretty good compressive strength, but the grout weighs so much,” Nussbaum says. “They had a little bridging of the grout, and it collapsed the outer pipe. It just flattened it right out.”

It’s a rare issue Lawless says was caused by a miscalculation in grout weight. The pipe was pulled out of the hole, replaced, and regrouted with no other problems.

“There are more steps, but once a crew knows what they’re doing and how to work together to put it in, it’s pretty simple,” Nussbaum adds.

The geothermal work for the project is complete and the building is expected to reopen later this year or early 2017.

Unity Temple is the third project where Nussbaum has used Rygan’s product to make geothermal a viable option without having to drill too deep. In all, Nussbaum has put more than 10 geothermal systems in Chicago landmarks during the past few years.

Geothermal is a popular alternative with owners of historic buildings—whether it’s a traditional system like the Bach House or a system like Unity Temple’s—and expects the trend to continue.

“The last thing (owners of historical buildings) want is this huge big modern piece of junk making noise, when you can have it running quietly in the basement,” Nussbaum says.

“All of the things that make geothermal an attractive solution are extra attractive to these types of clients.”

Jennifer Strawn was the associate editor of Water Well Journal from 2004 to 2007. She is currently in the internal communications department at Nationwide in Columbus, Ohio. She can be reached at

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