Radiant Ceilings

Chilled ceilings are a radiant technology that can be used to provide both cooling and heating. Generally, chilled ceilings are configured as a flat metal panel with a water pipe attached to one side in a serpentine pattern. Chilled or hot water is circulated through the water pipe. The thermally conditioned water transfers energy (heating or cooling) to the panel, which in turn transfers this thermal energy to the occupied space. The pipes heat or cool the metal panel, which then radiates that energy toward the building occupants.

Radiant heating and cooling systems at TELUS Spark: the New Science Center feature an “architectural cut in,” a panel cut to integrate into the structural elements. Photo courtesy of Price Industries

The thermal comfort and high efficiency achieved with radiant heating and cooling, as well as the flexibility and customization of the product, make it suitable for use in almost any application. Radiant panels are designed with a low profile to integrate into a variety of installations, from standard suspended ceiling systems to free hanging applications and surface-mounted applications on walls or ceilings. The panels are typically installed along perimeters, corridors, hallways, and aisle ways, or in interior spaces, with exposed linear panels provided when the ceiling space is not available, when a radiant panel installed or recessed into the ceiling is not feasible, or when the radiant panel is to be placed in an area with high ceilings.

Chilled Sails

Originally developed in Europe in the late 1990s, chilled sails are a relatively new technology in North America. Sails couple the radiant cooling effects of standard radiant panels with a convective component in cooling for increased thermal performance. The sails' unique shape gives them more surface area than a traditional radiant panel, increasing their radiant capacity and still achieving the high comfort of radiant systems. They allow air that has been cooled by contact with the sails to pass through openings between the blades, thus increasing the capacity of the unit and providing an effective means of dealing with the sensible cooling load.

41 Cooper Square, the newest addition to The Cooper Union for the Advancement of Science and Art, features an integrated spring clip chilled ceiling system. Photo courtesy of Nelson Industrial Inc.

The heat transfer between the sail to the room has two components: natural convection with the room air and thermal radiation with the room surfaces.

In cooling mode, a significant amount of the heat transfer occurs via natural convection as warm air rising due to natural buoyancy forces, passes over the chilled sails, cools and then sinks down into the occupied zone. As the air falls into the occupied zone, the convective cooling capacity of the sail is coupled with the radiant capacity of the cool sail surface, resulting in a cooling capacity greater than that of standard . In cooling, the approximate breakdown of heat mode transfer of chilled sails is 30 percent by thermal radiation and 70 percent by natural convection.

Chilled sails are a relatively new technology in North America. Photo courtesy of Price Industries

Like , sails can only handle the sensible portion of a building load and must be paired with a fresh air system for ventilation and latent load removal.

Characteristics

Chilled ceilings and chilled sails share several beneficial characteristics.

Architectural appeal. Chilled ceilings and chilled sails can add design elements into a space to provide both a practical function and aesthetic appeal. Available in a variety of surface finishes, profiles, and services, and chilled sails offer a sleek, streamlined profile that complements today's modernistic architectural designs while dovetailing with current green building goals. Chilled panels also offer architects sound-dampening qualities as they can integrate acoustic damping, or they can be silk screened to match acoustical tiles. In some instances, the chilled ceiling can even become a primary architectural feature in the building, essentially being a functional sculpture.

Energy efficiency. Radiant systems require less parasitic energy (pump and fan energy) to deliver heat. Using panels or sails to satisfy sensible room loads instead of all-air systems, greatly reduces the supply air volume required by as much as 60 to 80 percent, with the result of decreased fan power requirements and associated energy savings.

Indoor air quality. Depending on the application, under maximum load, only 15 to 40 percent of the typical overhead mixing system supply air volume in a typical space is outdoor air and is required to satisfy the ventilation requirements. The balance of the supply air flow is re-circulated air which can transport pollutants through the building from one space to another. Radiant systems transfer heat directly to/from the zone and are often used with a 100 percent outdoor air system which exhausts polluted air directly to the outside, reducing the opportunity for VOCs and biologically active airborne material such as flu to travel between air distribution zones. This characteristic makes radiant systems an ideal choice in buildings or rooms where air quality is critical.

Thermal comfort. Radiant heat transfer has been shown to condition a space more comfortably than convection. Since radiant heating/cooling uses minimum primary air quantities, air velocities are lower in the occupied space, minimizing draft risk.

Quiet operation. Because radiant panels and chilled sails have no moving parts, the only noise they produce comes from water moving through the copper piping. At typical water velocities, the noise produced by the system is nearly imperceptible. This allows radiant ceilings to operate more quietly than traditional all-air systems. Radiant panels and sails are also commonly integrated with acoustical panels, which can further reduce noise levels in a space.

Smaller services footprint. The reduced supply air volume of a hydronic system reduces ductwork requirements, resulting in the ability to reduce plenum heights. This allows radiant systems to be installed in tight spaces, and creates the potential for lower construction costs, higher ceilings, and more usable floor space. In addition, the air handling equipment is often downsized—saving cost and providing more flexibility in locating the equipment.

Reduced maintenance. Due to the reduction in moving parts and mechanical equipment associated with radiant panels, these systems have lower maintenance costs than all-air systems.