Radiant Ceilings

Other Literature/Studies
Barcol Radiant Ceiling (BRC)
Barcol Radiant Gypsum (BRG)

Basic

What is Radiant Cooling/Heating?

Radiant Cooling is based on the physical principle that bodies with varying temperatures exchange thermal radiation until equilibrium is achieved. Thermal radiation is electromagnetic radiation emitted from the surface of a body as a result of temperature differences. Since radiation can travel through a vacuum at the speed of light, it is not dependent on air movement to transfer large heat loads. The flux rate is a function of the temperature differential between two surfaces and the emissivity (ability to absorb and radiate energy) of the body materials.

An example of thermal radiation?

Heat exchanges between the sun and earth - hence the term solar radiation. How does this example relate to my radiant ceiling? During cooling mode, warm bodies (people, computers, lights, etc.) in the room emit heat which is absorbed by the cooler surface of the ceiling. Chilled water flows through a copper tube and aluminum heat conduction rail (HCR) mounted on the top side of the panels. The heat is absorbed by the cooler water and is transported back to a central chiller unit or heat exchanger.
During heating mode, warm water flows through the coils and heats the panel surface. The warm surface emits thermal radiation which is absorbed by the cooler bodies in the room.

Summary: In both cases, the flux rate does not dependent on air movement to transfer energy! The flux direction is always from the warmer body to the cooler body!

Concept of Radiant Cooling?

The basic concept of this system is to separate the tasks of ventilation and thermal space conditioning by using the primary air distribution to fulfill the ventilation and dehumidification requirements, and the secondary water distribution system to thermally condition the space. The system allows precise control of the space conditioning without impairing the air quality. The building control can, therefore, adapt swiftly to changing indoor/outdoor conditions while always maintaining a high quality indoor environment.

Benefits:

  1. High Energy Efficiency


    The specific heat capacity of water is four times higher than air. This means that the energy that 1 ft3 of water can remove requires an equivalent of 3,480 ft3 of air! Therefore, to remove a given amount of heat from a building, less than 25% of the transport energy is required to remove the same amount of heat compared to an all‐air system. Barcol Radiant Ceiling (BRC) systems operate at higher water temperatures than all‐air systems. This system allows for the use of heat pumps or chillers with very high coefficients of performance. Also, alternative cooling sources can be used to further reduce the electric power demand of the building.
  2. Highest Thermal Comfort

    The human body constantly adapts to the thermal environment by means of dynamic equilibrium adjustments to maintain homeostatic conditions. This thermoregulation involves radiation, convection, conduction and evaporation.
    The perceived thermal comfort is primarily defined by the distribution of these individual processes. Although the human heat load only accounts for a small portion of the peak cooling demand of a building, the effects of the cooling system on the heat balance are crucial. Due to the higher temperature differential between the body surface and the surrounding surfaces, there is an increase in heat transport by radiation. This results in a reduction of convection and evaporation, leading to a superior thermal comfort. The perceived ambient air temperature is generally 2°F lower than the actual dry bulb temperature. The set point can be adjusted accordingly, resulting in further energy saving potential.

    Why is thermal comfort important?
    The thermal environment has a significant effect on the performance of building occupants.*
    * Research shows that improving the thermal environment in US office buildings would result in a direct increase in productivity, worth $200 billion annually. Lawrence Berkeley National Laboratory
    2001, Wyon 1993, 1994, 1996, Fisk and Rosenfeld 1997.

    The quality of the indoor environment correlates to the health of building occupants.**

    ** The costs of absenteeism due to “Sick Building Symptoms” in US offices are estimated at $58 billion annually. Lawrence Berkeley National
    Laboratory (Vaughn 2001).

    Summary: Office employees spend a large part of their lives in space conditioned buildings. A high quality thermal environment not only benefits the health of the employees, but can increase the financial prospects of the employer and building owner!
  3. Significant space savings, both in equipment and space above the ceiling!

    By transporting only the air necessary for ventilation and dehumidification purposes, BRC systems significantly reduce both the volume and the velocity of air transported through buildings. Thus reducing the space necessary for the ventilation system and duct work. BRC systems only require about 25% of the building volume occupied by a traditional air‐conditioning system.

    Also Floor‐to‐floor building heights can be reduced by reducing plenum height from a typical 4‐8 ft to a quarter of the height. Alternatively, building occupants can enjoy spaces with higher ceilings. In addition to ceiling heights increasing, the size of the riser in the shafts of the building are reduced, which in turn increases the rentable floor area.

Building space management example:

Additional Benefits:


In new buildings:

  • At a given number of floors, the total building height can be reduced = reduced construction costs!
  • At a given building height, the number of floors can be increased = increased rental space

In existing buildings:

  • Increased flexibility through higher ceilings!
  • Cooling systems can be installed in buildings which were previously impossible to fit with a conventional all-air system!

Applications of Radiant Cooling:

  • Radiant systems are not limited to specific geographic regions. They can just as well be used in the tropics, as in moderate dry regions!
  • Provided the building envelope is moderately tight, the system be applied anywhere!
  • Radiant systems are suited for all types of commercial buildings, hospitals, schools, airports, hotels, etc.
  • Radiant systems are not limited to new buildings, but can just as well be retrofitted in existing buildings.
  • Radiant systems can be used in residential buildings, on the precondition that the building is ventilated to control humidity in human areas

The costs

On a first cost basis, the BA Radiant Cooling systems are in a competitive price range with all air systems (including mineral fiber ceiling panel system). On a long‐term basis, the BA Radiant Cooling systems offer significant benefits in terms of life cycle costs
  1. Lower energy costs due to higher efficiency
  2. Virtually no maintenance costs
  3. High quality long life product
  4. System can easily be reconfigured to adapt to changes in the floor plan layout!

For the Architectural: Design

The heat conducting rails and copper are mounted on ceiling panels and are not visible from the room. The system poses virtually no restrictions to the form, size, color, perforation, etc. of the ceiling panels!

The Barcol-Air radiant cooling system is not limited to only metal ceiling panels, but can also be applied in combination with other materials, such as gypsum ceilings. For very extravagant designs, the use of aluminum sandwich panels can also pose as an option. The panels are extremely stiff and lightweight, which allows very large spans (meaning distance between one hanging point to another), with minimum panel deflection.

BRC is available is a variety of shapes, including:

Round panels and square panels with different copper layouts to accommodate design load or openings in panel for lights, sprinklers, diffusers etc.

For the Engineer ‐ Radiant Ceiling layout example (1 loop in zone):

*Reverse‐Return piping with multiple loops or single loop is also possible.
Website Builder