A Man on a Radiant Cooling Mission
October 25, 2010
Over the last three decades, Dean Newberry, founding partner, Talbott Solar and Radiant Homes, Davis, Calif., has thought long and hard about radiant cooling systems. His goal has been to figure out how radiant cooling - which has long been used in commercial buildings - can be applied effectively in residential and other low-rise, light frame buildings.
Newberry started his quest for a viable radiant cooling system in the 1970s, when his work as a building trade’s consultant brought him into contact with passive solar homes that used roof pond and culvert wall systems to provide natural cooling. Knowing that these solutions would never have mass-market appeal, he spent the intervening 30 years studying various options and waiting for building science, materials, and methods to reach a point where radiant cooling could become a workable option.
About five years ago, Newberry realized that room-by-room load calculations per ACCA’s Manual J had finally reached a point where building load requirements could be met with radiant ceiling panels without hitting the dew point, which is critical in order to avoid condensation. According to Newberry, the limit on the temperature difference between the chilled water temperature and the room temperature set point can be no greater than 15 Btu per square foot per hour, and the room loads were coming in at closer to 10 Btu per square foot per hour. “We finally crossed the line and decided we could make this happen,” he said.
The result of Newberry’s determination is xLath™ hydronic radiant cooling and heating ceiling panels, which just came on the market earlier this year. The ceiling panels took first place in the cooling category of the Radiant Panel Association’s 2010 Systems Showcase, and Newberry is thrilled that his dream has finally come to fruition.
AN INVENTION IS BORNWhen Newberry realized the time was right to design a radiant heating and cooling system, he focused on figuring out exactly what was needed in order to successfully switch the system from heating to cooling. The answer was to invent a 16- by 24-inch self-furring radiant panel module, which leaves space for any approved ½-inch flexible tubing to be placed in the panel channel.
Made out of sheet metal with a high-emissivity coating to optimize heat transfer, the radiant ceiling panels are attached to the ceiling joists, then drywall is installed over the radiant panels. Attaching the drywall to the radiant panels allows good contact and thermal exchange through the ceiling, said Newberry.
The hot and chilled water needed for the radiant ceiling panels can be supplied by chillers, boilers, or heat pumps. “The equipment selection depends on the customer, their location, the types of energy they have available, their long-term goals, etc. With one of our clients we used a geothermal heat pump and with another we used a dual-purpose hot water boiler with shop fabricated chillers. The important point is that there are numerous solutions available in the marketplace that can be used with the radiant panel system.”
The radiant ceiling panels can provide 100 percent of the heating and cooling needed for a home, said Newberry, and no backup systems are necessary. “Some climates may require air handling, and again, there are multiple solutions for that. In some cases, we might install a central dehumidification system or multiple fan coil units or zoned heat pump air handlers. Depending on the climate, the energy available, the building design, and building loads, our industry has multiple ways to solve the issue.”
COSTS AND ENERGY SAVINGSNew technology is often more expensive, but Newberry states that the xLath was designed to be an extremely simple system that can be installed for not much more than what a forced air system costs. “Building envelopes are tighter now, and the requirements for quality ductwork have gone up dramatically, resulting in radiant cooling now becoming a financially viable option. The system doesn’t cost much more than a forced air system, and it can use about half the energy, depending on the climate.”
While the xLath system does not have an official efficiency rating from Air-Conditioning Heating and Refrigeration Institute (AHRI), “We know from the physics that the energy exchange between refrigerant and water is more efficient than refrigerant to air on an A-coil,” said Newberry. “In addition, the refrigerant cycle in our system is working against a smaller ΔT, so it is more efficient, and the fuses we put on our disconnects are 20 amp rather than 30 or 40 amp, because our equipment is much smaller.”
The radiant ceiling panels can be installed in new construction or retrofit applications, and they can begin to cool down a space in just about 20 minutes. “It takes about that long for the effects to go through the ½-inch drywall in the ceiling,” said Newberry. “As long as there is a call for cooling, the chiller cycle will cycle on and off. Under moderate loads, it will cycle on for 10 minutes and off for 30 or 40 minutes. Under high loads, it will cycle on for 10 minutes and off for 15 or 20 minutes. There is enough thermal mass in our system that we do not need a buffer tank in most cases, and we also do not short cycle our compressor.”
So far xLath radiant cooling and heating ceiling panels have been installed in 10 homes, and Newberry has more projects lined up and ready to go. “Most of our current jobs are homeowners who are doing a gut and overhaul on their existing homes. They’re excited about the technology, the major manufacturers are on board with the technology, and we think it is the best time for us to roll out this innovative system.”
For more information, visit www.talbottsolar.com or call 800-731-4541.
Publication date: 10/25/2010