Radiant Cooling Demonstrates High Efficiency, Greater Comfort
Radiant Gains Popularity in US as Benefits, Comfort Become Known
HVAC equipment accounts for about 40 percent of commercial building energy consumption worldwide, and as energy costs continue to increase, so will the need for higher-efficiency HVAC systems. In fact, Navigant Research forecasts worldwide revenue from energy-efficient HVAC systems will reach $33.2 billion annually by 2020.
Immensely popular in Europe, radiant cooling is steadily gaining popularity in the U.S. because of its potential to reduce energy consumption. According to Dave Desjardins, product manager, Viega ProRadiant Heating and Cooling, about half of net-zero energy buildings use radiant cooling to help them achieve the balance between energy consumption and renewable energy creation.
“A radiant system can distribute energy more efficiently because water is a better medium for transporting energy than air,” said Desjardins. “Also, a circulator that moves the water in a hydronic heating/cooling system uses considerably less energy. High-mass [concrete] systems are like thermal sponges. They can store energy that can be released throughout the day, so the system can be pre-charged during off-peak hours and cool throughout the peak cooling time. During some off-peak time there could be an off-peak electric rate that could be taken advantage of.”
Kirk Vigil, business development manager, Grundfos Pumps Corp., said, while radiant cooling is definitely a growing market, radiant heating is a more accepted concept, but only because it has been around longer. “We’ve heard more about radiant heating, and the PEX guys have spent a lot of time training and advertising the benefits of the product,” he said.
“Radiant cooling has more awareness in the commercial sector. In larger buildings, the energy dollars are much higher and more significant than residential applications. Developers and engineers are on a constant mission to reduce cost, which makes radiant heating and cooling more attractive. In residential applications, the driving force is comfort. Radiant systems are typically much more expensive than traditional forced-air systems and the energy savings are there; however, the dollar value does not seem to have the same impact as larger commercial applications. Another reason is radiant heating has been around longer, and we understand it. We are familiar with radiators and baseboard heating. Those appliances are not designed for cooling. We understand forced-air cooling. Radiant cooling is either unknown or a mystery to most people.”
Greg Cunniff, application engineering manager, Taco Inc., said chilled beams or radiant cooling has the ability to provide 30-40 percent in energy savings, which has helped drive the market.
“Typical air conditioning systems would need upwards of 10 air exchanges to accomplish a similar level of cooling within a facility,” he said. “With chilled beam or radiant cooling, we need only two air exchanges to pressurize, ventilate, and cool. So, you’re reducing the amount of air substantially, and substituting water to distribute Btu much more efficiently.
“It’s also more comfortable because you have less evaporative cooling,” Cunniff continued. “When you’re warm, you begin to perspire; the body loses heat through evaporation. And, if air is blowing over you, you get colder, even uncomfortable. Traditional air conditioning systems move a lot of air around the building, trying to cool it. As a result, people in those spaces are over-cooled. The temperature may be okay, but they’re feeling cooler. So, by eliminating this substantial airflow, people are much more comfortable. It’s two for one. Radiant cooling is efficient and comfortable. That’s the driving force [in the market] right now.”
Another advantage to radiant cooling is lower maintenance costs throughout the equipment’s lifespan. “Radiant cooling uses pumps instead of fans,” Cunniff said. “With radiant cooling, you have less equipment to maintain. So, over time, radiant cooling systems should have less equipment and maintenance costs. Here in the U.S. — because we don’t yet have decades of experience to draw on — we’ve yet to prove it out. In Europe, they’ve been doing [chilled beam cooling and radiant cooling] for 20-30 years. They’ve been able to realize those kinds of benefits. But I can say that over the past few years, with many systems successfully installed in commercial structures here in the U.S., the results are truly amazing. The technology is durable and efficient while offering people inside a level of comfort that’s hard to describe.”
Rebutting the Myths
According to Devin Abellon, business development manager — engineering services, Uponor, one of the things that has caused engineers to pause when considering radiant cooling is “the perception that radiantly cooled slabs are prone to condensation. However, now that the industry has a much better understanding of how radiant systems work and are controlled, this concern has lessened considerably.”
Rich McNally, senior sales manager — eastern region, Watts Radiant, said there is a trick to creating radiant cooling systems “You have to cool stuff in order to create a thermal delta so that heat energy leaves the building or your skin at a high rate of speed, you’re always under the threat of condensing. There’s a trick to do it properly. You have to watch the dew points, and you have to maintain the dew point. This is not always the case, but, in areas with relatively high humidity, you have to be real careful to never allow any of these radiant cooling surfaces, whether they’re panels or beams, to go below the dew point. Otherwise, as you might imagine, you’re going to have wet surfaces. That means the wallpaper lands on the floor, and grandma lands on the floor because the floor is suddenly slippery.
“If you were in West Texas or Nevada — somewhere very dry and hot — the need for dew point is very low. But, if you were in Michigan, it gets humid there, as it does on the east coast. So, obviously, you’re going to have to be real careful of dew point. It’s pretty neat, and it can be very effective and fairly efficient, depending on how the heat’s rejected. You have to be careful, that’s all. It’s something that you can absolutely overcome, it just has to be part of the equation.”
McNally said he believes structures should be built around the cooling system. “Not 100 percent, but to some extent. You have to be very cognizant of the fact you’re going to have radiant cooling, so you really have to bear that in mind as you design your structure, regardless if it’s residential or commercial.”
Looking to the Future
Desjardins said more and more radiant cooling systems are being integrated into commercial projects as a result of reduced energy consumption requirements.
“In the next few years, stricter requirements for reduced energy consumption will continue, occupant comfort will need to be considered when selecting building systems, and integrated controls with radiant cooling will be much better understood.”
Abellon believes there will be an increase in new and innovative products offered by manufacturers as interest in radiant systems grows.
“One example is Uponor’s Radiant Rollout Mat, a custom-designed, pre-manufactured radiant mat that significantly reduces installation time,” he said. “Another trend we are seeing is in the areas where radiant systems are being applied. Radiant floor cooling systems can be very effective in areas such as lobbies and atria with high, direct solar-heat gains. So, we’ve seen numerous applications where radiant cooling is used specifically for these types of spaces.
“We are seeing more and more use of radiant cooling systems, not just for these special areas, but as the primary means of cooling to serve the entire building,” Abellon continued. “A growing number of exciting, high-profile projects incorporate radiant cooling as an energy-efficient alternative to forced-air HVAC systems. As the list of successful case studies continues to grow, we see radiant cooling becoming a very well-accepted system for high-performance buildings. As contractors become more familiar with how to install radiant systems, we see the cost involved coming down, as well.”
McNally said he definitely sees radiant cooling growing in the commercial market, but not so much in residential. “It makes more sense [in commercial] typically because of the construction type. They’re typically using materials that lend themselves better to radiant heating or radiant cooling. They have big, open floor plan areas that grant the availability of large surfaces for heat absorption or heat emission.”
Radiant cooling will not have a huge impact on the residential market just because of the way the U.S. builds homes compared to Europe, according to McNally. “Plus, residential construction is hottest in the multifamily area. There’s not a whole lot of developers doing radiant anything in multifamily projects.”
McNally said radiant cooling is also a great solution for buildings where solar gain is a problem.
“Imagine you’re a receptionist in a Manhattan insurance office out in the middle of an expanse of tile with a big, expansive glass wall. It’s zero degrees and it’s winter, so the cooling and heating issue becomes a big one. You’re blowing cool air into that room because you have solar gain. All of a sudden, one side of you is hot, and the other side is cold. Statistically, you’re comfortable, but, realistically, you’re not. Radiant cooling in those situations can make a lot of sense. You have relatively low humidity because it’s winter. You’ve got solar gain, and you’ve got to get rid of that heat somehow. For some designers, it’s made a lot of sense to do it that way. It’s pretty sneaky; it’s pretty cool.”
Vigil said the key to the growing radiant cooling market is awareness.
“As manufacturers create new, innovative products in cooling, the challenge is to educate the industry and create acceptance for a new way of doing things. We are creatures of habit, and the way we have always done it is safe and comfortable. Innovators will get on board quickly with new technologies, but converting the critical mass of engineers, builders, and building owners takes time, energy, and a history of success.”
Publication date: 1/19/2015