In Europe and Australia, chilled beam systems have been used in the commercial market for decades, but in the U.S., they have been slow to gain traction. The reason for that may be an overall lack of awareness of the technology, but that may be changing soon. A recent report states that the global chilled beam system market is forecast to grow at a compound annual growth rate (CAGR) of 11.14 percent between 2015 and 2020, and North America is expected to be the fastest-growing region.
That is good news for manufacturers as contractors and building operators continue to consider chilled beam systems as solutions in net-zero-energy facilities. “All levels of government, commercial businesses, hospitals, universities, and building owners are continuously looking for ways to operate more efficient buildings and thus save money,” said Steven Lamica, lead applications engineer, Dadanco, a Mestek company. “Chilled beam systems can be a great avenue for them to achieve this goal.”
Sales of chilled beam systems have grown steadily over the past 10 years, with much of the growth occurring in government, health care, and educational buildings, said Nick Searle, chief engineer and sales, Titus. “These types of applications are ideal for active chilled beam systems, which work well in environments that may have moderate-to-high sensible heat ratios. They also work well in building retrofits, where space for new mechanical equipment may be limited.”
An active chilled beam is a combination air-water system that uses the energy conveyed by two fluid streams (air and water) to deliver the required cooling or heating in a space, explained Lamica. “In this type of system, primary air is continuously supplied to the chilled beam at a constant or variable flow at rates potentially as low as the ventilation air requirements. The primary air is cooled or heated to handle a portion of the temperature-driven room sensible loads. In the summer, it is cooled and dehumidified sufficiently to handle all of the internally generated moisture-driven room latent loads.”
Passive chilled beams are primarily air and cooling-only products that are used to cool a space utilizing convection. “A beam or coil is suspended from the ceiling and fed chilled water,” said Lamica. “As the coil chills the air around it, the air becomes denser and falls to the floor. Due to buoyancy, hot air rises to replace the cooled air and the convection cycle continues.”
While chilled beam technology has not changed much over the years, the way in which the systems are applied and controlled has evolved. “For instance, chilled beams are gaining more popularity with engineers who are pushing toward LEED certifications,” said Steve Ulm, marketing director, Semco LLC. “Newer systems allow for tighter control of zones of chilled beams and help reduce the overall cost of the system as well.”
Building owners and managers are often price sensitive, and compared to a conventional HVAC system, the first cost of a chilled beam system is similar or slightly higher; however, it can offer significant long-term savings, said Searle. “It is also a compact system, which makes it suitable for building renovations with limited floor to ceiling heights. In addition, the system provides a constant airflow rate to the space, which results in an even temperature across the space for a quiet, comfortable environment. Also, chilled beam systems have few moving parts and feature coils that operate dry, which minimizes maintenance.”
But energy savings is the real driver behind the interest in active chilled beam systems. “When compared to all-air systems, such as VAV [variable air volume], the reduction in primary airflow is dramatic,” said Lamica. “The power used by the fans is the main difference. With an active chilled beam system, the central air-handler supply [and return] fans are handling much less air and therefore require much less energy and can often be downsized. Chiller operating hours/loading can also be reduced if a water-side economizer is employed to serve the active chilled beam secondary water loop.”
Just like any other type of HVAC system, the benefits of a chilled beam system are linked to its proper installation. An improperly installed chilled beam system may not provide the energy savings or comfort expected by the end user, and, in some cases, can result in bigger problems, such as condensation.
“Humidity and dew point must be considered when designing a chilled beam system, as high humidity/dew point can cause condensation,” said Ulm. “If an active condensation control method is not being employed, it is possible to get ‘rain’ in the room.”
To avoid this scenario, many chilled beams are used in conjunction with a dedicated outdoor air systems (DOAS), which precisely control the humidity and ventilation rates in the space. With the installation of dew point sensors, the building management system can monitor the humidity and reset the DOAS air dew point or reschedule the chilled water temperature if the space dew point rises above a preset level, said Searle. “Room dew point monitoring enables precise control of the amount of outside air latent cooling at the DOAS unit, which further reduces energy costs.”
This may sound complicated to some, but contractors who are not familiar with the design and installation of a chilled beam system should not be scared off, because these systems are fairly similar to install as more traditional systems. “Active chilled beams still utilize ducting to feed the beams with fresh air, albeit the ducting is much smaller than what they may be used to,” said Lamica. “And most contractors are familiar with how to install water piping that is used to feed the beams, and they know how to hang HVAC-related products from ceiling structures, so chilled beams do not differ here either.”
In addition, the pipework that provides the chilled or warm water to the beams is similar to the hot water distribution pipework used for VAV with water reheat, noted Searle. “The only difference is that a chilled beam system has more pipework but less ductwork than a VAV system. Some designs use a six-way valve to regulate both warm and chilled water to two-pipe chilled beams, which many engineers and contractors are unfamiliar with, but they still require the same installation techniques as two- and three-way valves. The chilled beam units can also be quite bulky, particularly 8- and 10-foot long units, but these can be installed with conventional site lifting gear.”
Ultimately, contractors should consider adding chilled beams to their offerings, because demand for these types of systems is expected to grow over the next few years. “We see the market demand continuing to grow as more and more HVAC professionals find out about how to apply this technology, which has been in use for almost 40 years in Europe,” said Ulm. “Growth will also come as legislation continues to increase and industry organizations continue to push for better IAQ and energy efficiencies. This will lead to renewed interest in chilled beams, which are efficient, environmentally friendly, and effective when used as part of an overall air system design.”
SIDEBAR: CHILLED BEAMS EXCEL IN SCHOOLS
Studies have shown that excessive noise levels can adversely affect student performance. Conventional HVAC systems typically used in schools today, including fan-powered variable air volume (VAV), fan coils, and unit ventilators, rarely meet prescribed background noise level requirements — ANSI standard S12.60 for classroom acoustics requires a maximum background noise level of 35 dBA (about NC-27).
Furthermore, student performance is affected by space humidity and ventilation levels. HVAC systems, whose primary airflow rate is modulated while the classroom is occupied, often do not comply with the requirements of ASHRAE 62.1-2013. Ventilation airflow rates are difficult to maintain at part-load conditions by modulating the primary airflow rates. Chilled beam systems are designed with zoned-based hydronic-heating and/or cooling devices that complement the conditioning of the primary air-ventilation system, which allows for the optimization of all heating, cooling, and ventilation functions and provides opportunities for savings in energy, ceiling cavity space, and maintenance as well as increased occupant performance.
Most conventional HVAC systems depend on the delivery of large volumes of air to condition the classroom. Chilled beam systems typically reduce ducted air requirements by relying on their integral heat transfer coils to offset most of the space-sensible cooling and heating requirements. Since water is typically more efficient for space cooling and heating than air, chilled beams tend to use less overall energy than the other options available, such as VAV, variable refrigerant flow (VRF), and fan coil units.
Since chilled beams allow ducted classroom airflow rates to be reduced to those which are required for space ventilation and latent cooling, they are ideal for use with 100 percent dedicated outdoor air systems (DOAS). This allows the beams to provide a constant volume of ventilation air to the classroom at all times.
Information courtesy of Jeff Scanes, director, air distribution product sales, Johnson Controls Inc.
Publication date: 10/24/2016