ADVANTAGES:
- Operational costs are reduced for the mechanical chilling system since cooled ceilings operate at relatively high temperatures (average surface temperature of 16°C or 61°F).
- Chillers can operate at higher temperatures resulting in an increase in efficiency and reduction in energy costs.
- Radiant panels can be used as both heating and cooling panels reducing the amount of equipment and piping required compared to conventional heating & cooling systems.
- Cooled ceilings are silent and virtually draft free
since air flow volumes are reduced compared to conventional systems (typical radiantly cooled office requires 2 to 3 air exchanges/hour compared to 6 to 10 with conventional systems) - Radiant cooling panels can be retrofitted into false ceiling of older buildings as the plenum space requirement is minimal relative to fan coil units or VAV systems.
- Smaller plenums result in savings in building height (1’/floor) compared to air conditioning systems.
RADIANT COOLING
The heat transfer occurs between the space and the panels through a temperature differential. 
However, unlike radiant heating, the colder ceiling is absorbing thermal energy radiating from people and their surroundings. The major difference between cooled ceilings and air cooling is the heat transport mechanism. Air cooling uses convection only, whereas cooled ceiling use a combination of radiation and convection. This amount of radiative heat transfer can be a s high as 55% while convection accounts for the remainder. With cold ceilings the relative heat transfer occurs through a net emission of electromagnetic waves from the warm occupants and their surroundings to the cool ceiling. On the other hand, convection first cools the room air due to the contact with the cold ceiling, creating convection currents within the which transfer the heat from its source to it is absorbed.
Since air quality must be maintained and radiant panels remove only the sensible heat from the space, radiant cooling panels are used in conjunction with a ventilation system. The ventilation not only ensures the air quality to recommended levels but also regulates the latent, or moisture load, of the space. To prevent high humidity levels within a room, the supply air must be drier than that of the supplied space especially in light of additional sources of moisture within the room. Consequently, outdoor air must be dehumidified which is usually done by cooling to a dew point of approximately 15°C (59°F). If the environment is dry, the ventilation system is used to humidify the air. Since the ventilation system is used only to maintain the air quality and to regulate the latent load of the space, the air flow required is small relative to conventional cooling systems. The best results are usually attained with a straight displacement ventilation system with no air recirculation. This system typically supplies air through outlets near or at floor levels at temperatures below that of the room air which provides for a uniform layer of fresh air at the floor level. In turn, people and other heat sources will provide for a passive convective flow of fresh air to the ceilings where it can be exhausted. With this reduction in air flow and the fact that radiant panels can operate at a relatively high surface temperatures (mean temperature of 16°C or 61°F), radiant cooling is a more comfortable way of cooling a space than the conventional cooling systems. Therefore, in a radiant cooling ceiling, the panels provide most of the sensible cooling while the air system provides ventilation and air moisture control.
A cooled ceiling operates in direct proportion of the heat load in the room. Typically, a person sitting at a desk will emit 130 W of energy while a computer emits 90 to 530 W to its surroundings. The greater the number of people and/or appliances and exposure to sunlight, the greater the temperature gradient and therefore an increased capacity of cold ceiling. Generally, cold ceiling are able to handle between 100 and 225 watts per square meter with up to 50% of the ceiling space utilized for cooling.
Condensation on the surface of the panels is not a problem with radiant cooling. Since condensation of water occurs when the dew point temperature is reached, proper water temperatures control will help avoid any condensation. To prevent the formation of condensation, a sensor monitoring the dew point temperature of the room used in conjunction with a controller which modulates the inlet water temperature accordingly. Therefore if a risk of condensate is present, the water temperature is raised or the water flow is shut off. However, since the lower the panel’s temperature is, the more work the panels do, the inlet temperature should be determined to be as close as possible to the room’s dew point temperature. Consequently, the cooling capacity of a radiant cooling system is generally limited by the minimum allowable temperature of the inlet water relative to the dew point temperature of the room air.
If the panel area required for cooling covers most of the ceiling (70% and more), a total ceiling is needed. In a total ceiling system, the panels must be perforated and covered with acoustic blanket insulation.
Ceiling cooling panels can come in a variety of designs and configurations. Panels can be suspended, lay in type or even made into a design feature.
Available Downloads:
Radiant Panels & Chilled Sails – Architectural Brochure
For addition information: info@rdes.ca