Nearly 90 years ago, with just a handful of animals, the Tulsa Zoo opened its gates to the public. Since then, the campus has grown remarkably and now spans 84 acres and serves as the home to more than 400 animal species.

In 2012, zoo officials began the development of a 20-year master plan for extensive renovations. Originally built in the 1960s and 1970s, most exhibits were ready for makeovers.

During one of the zoo’s first projects in 2012, Cary Pestel, owner of Tulsa, Oklahoma-based Boone & Boone Sales, the manufacturer’s representative firm for the job, assisted engineers with the specification mechanical equipment to heat a new giraffe barn.

The state-of-the-art barn is heated with 8,500 lineal feet of half-inch Watts RadiantPEX+. Zoo personnel can change the floor temperatures at any time, should the need for warmer or cooler floors arise.

Pestel was called back in 2014 for a new white rhinoceros barn and hospital area. This time, he specified 10,000 lineal feet of half-inch RadiantPEX+ with Watts hydronic control panels.

“The radiant flooring is the main source of heat for the building,” said Joe Barkowski, vice president of animal conservation and science, Tulsa Zoo. “While the rhino barn has additional sources of heat, the radiant provides the necessary heat in cold weather for the rhinos.”

This method is most beneficial for large animals as they receive more direct heat “coming up” from the ground as opposed to forced air that radiates down from above (unlike primates who can climb to different levels, for example.)


Today, the zoo’s most anticipated addition is its Lost Kingdom exhibit. When complete, the colossal, $20 million exhibit’s environment will transport guests to stone-hewn Asian ruins, deep in the jungle.

Komodo dragons, Chinese alligators, Siamang monkey, binturongs, snow leopards, and Malayan tigers will call The Lost Kingdom home. The creatures have the luxury of choosing between indoor and outdoor areas any time they please, and guests have the opportunity to see them behind the scenes like never before.

More than satisfied with the radiant heat solutions for past exhibits, zoo officials chose to rehire Boone & Boone for the Lost Kingdom project.

Radiantly heated ‘hot rocks’ will be strategically placed throughout the Komodo dragon and Malayan tiger exhibits — both inside and out.

According to Barkowski, Komodo dragons are ectotherms, meaning they’re dependent on external sources of body heat, like the sun, to regulate their temperatures by basking or seeking shade.

Malayan tigers derive from an equatorial climate, where hot and humid conditions are the norm to the critically endangered jungle cats.

Greg Sutcliffe, engineer at Tulsa-based Phillips + Gomez, said, “The heated rocks will be strategically located to provide optimal viewing for guests while also offering animals the opportunity to seek warmth at any time.”

In the exterior exhibits — one for the komodo and two for the tigers — below the surface of the man-made rocks, Watts Radiant ProMelt electric snow and ice melt cable will heat the surface, keeping them warm and dry during even the coldest of winters.

More than 50 lineal feet of the ProMelt snowmelt cable is encased in each of the 24-square-foot tanning beds, dishing out 50 W per square foot.


“Typically, out of the factory, cold leads — those parts of the wired ProMelt product that do not heat — are 10 feet long,” explained Pestel. “These lengths of braided steel wire lead to the heating elements of the ProMelt cable. For the job at the zoo, they needed cold leads that were that much longer — 50 feet, in fact. Watts Radiant did that for us with no questions asked.”

“In each of the hot rock applications, dual-sensing tekmar 519 sensors help to govern the temperature of the rocks using pulse-width modulation technology, which allows precise control of heat to maintain surface temperatures ideal for the critters,” added Bob Rohde, project manager at Tulsa-based McIntosh Services Inc., which served as the project’s mechanical subcontractor. “The tekmar 519s send a signal to a Watts Radiant controller, which activates or deactivates power to the ProMelt wires encased in the concrete.”

“Tulsa winters aren’t anything at all like the Komodo dragons’ natural monsoon climates of Indonesia,” added Barkowski. “Their body temperatures are roughly the same as the ambient temperature, so providing them with the warmed rocks is not only necessary for their health, it helps to replicate their natural environments, too.”


Crocodile species benefit from laying directly on a warmed surface. In the Chinese alligator exhibit, the sources of warmth are three in-slab, hydronically-heated radiant zones encased in concrete.

“The largest of the Chinese alligator’s concrete radiant zones is covered with a layer of sand, where nesting will take place and females can lay up to 40 eggs,” explained Averill.

The zones provide the endangered reptiles with more than 100 square feet of warm area to bask in year-round. These spaces are heated by 425 lineal feet of half-inch Watts Radiant barrier PEX.

“All of the Lost Kingdom’s interior radiant zones and hot rocks are hydronically heated,” added Pestel. “In-slab sensors send signals back to Watts Radiant HydroNex panels, which pull water from two 50-gallon, 40,000-Btu Bock electric water heaters that are tasked with heating fluids for all of the interior radiant zones.”

A Bell & Gossett PL-30 circulator, in-line air separator, and expansion tank are installed on one of the HydroNex panels. Also, Miljoco pressure gauges and thermometers are included, which are typical for any closed system.

“While the entire Chinese alligator exhibit will have forced-air heat to maintain constant temperatures, animals, like people, prefer to have options,” said Barkowski. “If they’re too warm, the gators can access the pool. If they’re too cool, they can move to a heated area to absorb the heat directly.”

Interior areas of the Malayan tiger exhibits have received in-slab radiant heating, in addition to the exterior hot rocks. There, three separate hydronic radiant heat zones, served by 400 feet of half-inch RadiantPEX+, provide the tigers with warmth whenever they need it.

Zoo creatures won’t be the only ones happy with the upgrades. With the animal dens, stalls, and dayrooms made visible to guests, opportunities to view animals will be greatly improved.

The zoo relocated an on-campus restaurant, the Trunk Stop, to reside next to the Lost Kingdom, where floor-to-ceiling glass walls will allow guests to see into the exterior tiger exhibits while dining. Talk about dinner and a show.

Information courtesy of Rachel Ruhl, an account manager and writer for Common Ground. Ruhl writes about HVAC, hydronic, plumbing, mechanical, radiant heat, geothermal, solar, and broad building systems industries. For more information, call 717-664-0535 or email

Publication date: 2/20/2017

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