Most people remember classroom learning at school as boring when compared with going on a field trip. Just mentioning the possibility that we might get out of the school building and go to the science center or nature conservatory could energize the class for days. Field trips are a lot more fun for students and experts say they teach critical thinking, historical empathy and tolerance. Teachers say they encourage students to try new things, reduce phone texting and gaming as well as build social interaction. 

The San Francisco Exploratorium website says, “We invite people to discover for themselves how the world works. Step inside a tornado, play with light and sound, build an arch, see what fruit flies and zebrafish look like under a microscope, measure tidal currents in the [San Francisco] Bay or explore more than 650 hands-on exhibits.” 

“The best way to learn about anything is by doing,” says business magnate and philanthropist Richard Branson.

Exploratorium Cooling in San Francisco

“It was quite a departure at the time but we knew it would work and decided just to do it,” says Bill Schwartz, vice president for the Osborne Co., consulting engineers for a new radiant cooling and heating system at the Exploratorium. “Once this very large project was done and proven, along with a few others, we found the confidence to embrace radiant cooling. I think it spurred a movement in the Bay area. Everybody learned. There are not many new buildings going up now without some radiant cooling in the design.”

When the Exploratorium wanted to expand, the City of San Francisco offered Piers 15 and 17 on the waterfront. The catch was that the massive Pier 15 shed, built more than 100 years ago, had been vacant for a while. It would need to be completely gutted. New HVAC systems were installed for more than 200,000 sq. ft. in the facility.

Today, it houses exhibition space for a half million student and tourist visitors each year, a mezzanine level for classrooms, conference rooms, office space and numerous outdoor attractions. The Exploratorium is cooled and heated by using the San Francisco Bay as a heat sink, which saves about two million gallons of water each year that otherwise would have been consumed by chillers. 

Instead, eight 50-ton Multistack VME II electric water-to-water heat pumps and a pair of heat exchangers supply a network of cross-linked Uponor PEX-a tubing embedded in concrete slabs on two levels. Each of the 82 zones has its own control valve and thermostat. The system saves 94 percent on electricity for cooling, 55 percent on electricity for heating and 57 percent over ASHRAE 90.1 requirements. 

 “We learned some new things,” says Joe Wenisch, project manager for the Integral Group, which installed the system. “We learned how the radiant rollout mats could save a significant amount of time on these large projects. Tying individual tubes is labor intensive. The mats made a big difference.”

Estimates on how much faster vary from 50 percent to 80 percent, according to installers and manufacturers.

The team undertook a year of logging the Pier 15 water temperature to analyze energy losses and verify that loads could be met by the system as designed, no matter the season.

“We confirmed that you can definitely do cooling using water-source radiant systems in San Francisco,” Wenisch notes. “We had some challenges with the salt water, so that side requires a different type of maintenance. I think the museum is learning that a huge net-zero building is doable but not easy because it keeps adding more exhibits, which use energy. They also had to figure out how to keep the seabirds from soiling their solar panels.” 

The building is polished concrete for the most part, with limited use of carpeting. Installers laid out tubing about 3 in. below the slab surface, which allows Exploratorium exhibits to be anchored without interfering with the cooling system. In total there are 13 in. of concrete and two layers of rebar due to the requirement for earthquake protection. 

“With these large underfloor systems, you have to learn to work with the structural engineering team,” Schwartz says. “But it’s all worth it. There is very little maintenance on these systems. They’re highly efficient and they last for 100 years.”

Ceiling Slab Radiant Heat in Chicago

Another place for learning, in a somewhat more volatile climate, is the Richard J. Klarchek Information Commons, a digital library at Loyola University on the far northeast side of Chicago. It also employs radiant hydronics in a slab but this time in the ceiling — and with a few other differences. The architects, Solomon Cordwell Buenz, were concerned that the university’s expansion was going to displace a green field. They wanted to ensure that in exchange, students would discover a building both highly connected with nature and respectful toward the environment. 

This meant a low-energy building that felt like an outdoor space. The hydronic system was combined with a panorama of triple-pane, argon-filled windows facing Lake Michigan, an underfloor ventilation system and windows that open to let the breeze and the sound of the waves in. They can only be opened by the control system and there are four different seasonal modes.

For 202 days of the year (with temperatures from below zero to 50 F), the natural ventilation system is shut off. Hot water from the boiler is pumped through 80,000 ft. of REHAU Raupex tubing embedded in the vaulted concrete ceiling, heating up the ceiling slabs, while the underfloor ventilation system moves warm air through the space. 

“It’s easy to heat this building because it’s packed with computers and people,” says Don McLaughlan from Hillside, Ill.-based Elara Engineering, designers of the system. “We just heat the perimeter. In the other seasons, it’s a little more complicated. With radiant heating, control is very important because with the slab you can’t shift temperatures quickly and you can’t have condensation. At Loyola, we measure the dew point at four points on each floor to prevent the ceiling temperature from having less than a three-degree differential.”

For about 52 moderately cool, low-humidity days, (50 F to 68 F), cooling is achieved with 100 percent outdoor air. The rooftop weather station triggers the controls to automatically open small operable windows on the east and west sides. For 62 warmer days (68 F to 75 F), the radiant ceiling system provides supplemental cooling in conjunction with the outdoor air. It circulates unconditioned 60 F to 68 F water from the university's nearby chilled water plant. The concrete slowly releases cool thermal energy over time. 

“In hybrid mode with the windows open, we use an even wider margin of five degrees,” McLaughlan says. “The staff has to be trained to use the building management system properly.”

During about 50 hot, humid Chicago summer days (75 F to 95 F), the building operates in full cooling mode. East-facing windows are closed. West windows remain open to exhaust the warm air out of the interior through a double-wall system. The interior is cooled from both above and below by the radiant ceiling and the underfloor system, using displacement ventilation. In various modes, the automatic blinds on the east and west elevations track the sun's movement and adjust as needed.

McLaughlan points out that although the control system is a key achievement, the building is innovative because the ceiling slabs were prefabricated in a factory. They produced 80 panels per floor, each sized at about 30 ft. by 8 ft. to fit on a flatbed, shipped to the site and craned into position. 

It is one of the first examples of precast radiant-embedded concrete slabs but it’s unlikely to be the last. Prefabrication is expected to penetrate the construction industry in numerous ways in the coming years.

Radiant Panels for the Port of Portland 

Another highly efficient building took advantage of a radiant system in the ceiling but not in concrete slabs. A three-story, 205,500-sq.-ft. port office at the Portland (Ore.) International Airport sits on top of a seven-story parking complex. The weather conditions and unique architectural design, intended to suggest an airplane hull, posed some challenges for Brad Wilson’s team at PAE Engineering.

They selected the lightweight ceiling-tile style of radiant panels, partly because “with this design we could only install so much HVAC at the perimeter and the panels offer a lot of cooling per square foot,” Wilson explains. “They worked well with this design. It was almost as if saving peak load was more of a consideration than saving energy. In some projects, radiant is a driver for the thermal efficiency of the envelope, although this building offers all the right complementary technologies.”

The radiant panel road has been a long journey for Wilson. He recounts a time when he was laughed at by fellow students in Leeds in the UK after he said Americans were not yet using radiant ceiling panels. “That was 16 years ago,” he recalls. “I ended up doing a thesis on them and now I design them into buildings.” 

Wilson never stops trying new things and learning by doing. “We use a high aspiration diffuser nozzle that ensures ventilation air gets to the occupants,” he noted. “And we’ve found a way in decoupled systems to blow some air across a radiant panel to get some extra conditioning energy out of it. … Along the same lines, right now we’re looking at a new product called a Wave. It’s a kind of metal radiant ceiling panel that also offers some convection.”

The Port Building has an Energy Use Intensity (EUI) of 46,000 Btu/ft²/yr., about 40 percent less than the average office performance of the national Commercial Buildings Energy Consumption Survey. Calculate EUI by dividing the total energy used by the building in one year by the total gross floor area of the building. 

The facility uses 30 percent less energy than an office built to the Oregon code (ASHRAE 90.1). Beneath the building, two hundred geothermal wells reach 300 ft. down, providing ground-source heating and cooling to the heat pumps serving the radiant system. “Ground-source temperatures work well with the limitations of radiant panels,” Wilson says. “It's a highly efficient way to go.” 

The building’s dedicated outdoor air system handles ventilation and dehumidification; it also recovers heat energy from building exhaust air. 

Wilson says you have to optimize efficiency and manage other considerations. “It’s tricky; it needs to be well-thought-out,” he explains. “You can’t have condensation and you don’t want thermal asymmetry, also known as ‘hot head syndrome.’ Design temperatures and applications are important with radiant panels.” 

Resurgence

Radiant hydronic systems are certainly not new but as these three projects show, they keep improving and designers continue to innovate. In preparing this article, we found other great projects such as these all around the country, including residential applications, which haven’t been addressed here. Could it be that radiant hydronics is finding new believers? 

Renowned scientist Loren Eiseley said: “If there is magic on this planet, it is contained in water.” Several of the hydronic champions we talked to mentioned water’s high specific heat capacity and thermal conductivity. In addition to energy efficiency and saving chiller water, hydronic systems can often avoid fossil fuel dependence and seem to work trouble-free for decades. Could they seriously threaten the dominance of forced-air systems in North America? 

There is some evidence of improving market penetration. According to Markets and Markets research, the global underfloor heating market was valued at $4.65 billion in 2014 and is growing at nearly 9 percent each year through 2020. Europe is a little bigger and more active than America but not by much. But enough with the statistics.

Attention students! Stop reading about boring market projections and the theory of radiant design. Stop listening to me drone on. Get out of the office and into the field. It’s field trip time! Just do it. Install some radiant systems. Confucius said: “I hear and I forget. I see and I remember. I do and I understand.”