• What is Radiant Cooling / Heating?
• Concept of Radiant Cooling?
• Benefits of Radiant Cooling?
• Applications of Radiant Cooling?
• Costs of Radiant Cooling?
• Architectural Designs with Radiant Cooling?
What is Radiant Cooling / Heating?
Radiant Cooling is based on the physical principle that bodies with varying temperatures exchange thermal radiation until an equilibrium is achieved. Thermal radiation is electromagnetic radiation emitted from the surface of a body as a result of its temperature. Since radiation can travel through 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 2 surfaces and the emissivity of the body materials (ability to absorb and radiate energy). An everyday example of thermal radiation?
E.g. heat exchange between the
Sun andEarth (hence the term solar
radiation)
How does this example relate to my
radiant ceiling?
Cooling Mode : Warm bodies (sun =
people, computers, lights, etc.) in the
room emit heat, which is absorbed by
the cooler surface of the ceiling (earth).
Chilled water, which flows through
heat conduction rails mounted on the
top side of the panels, then transports
the heat to a central chiller unit.
Heating Mode : Warm water flows
through the coils and heats the panel
surface. The warm surface (sun) emits
thermal radiation which is absorbed by
the cooler bodies in the room (earth).
Summary: In both cases the flux rate not dependent on air movement to transfer energy! The flux direction is always from the warmer body to the cooler body!
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.
High Energy Efficiency!
The specific heat capacity of water is 4x times higher than air. Or, the energy that 1 ft3 of water can remove requires an equivalent of 3480 ft3 of air! Or, to remove a given amount of heat from a building, less than 25% of the transport energy is required, in comparison to an all-air system to remove the same amount of heat. RC systems operate at higher water temperatures than all-air systems, which allows the use of heat pumps or chillers with very high coefficients of performance (COP values), or alternative cooling sources to further reduce the electric power demand of the building.
Highest Thermal Comfort!
The human body constantly adapts to the thermal environment by means of multiple dynamic equilibrium
adjustments, to maintain homeostatic conditions. The thermoregulation involves radiation, convection,
conduction and evaporation. The perceived thermal comfort is primarily defined by the distribution
of the 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!
The increased heat transport by
radiation, due to higher temperature
differential between the
body surface and the surrounding
surfaces, results in a reduction
of convection and evaporation,
which in turn leads to a
superior thermal comfort.
The perceived ambient air temperature
is generally 2°F lower
than the actual dry bulb temperature.
The setpoint can be adjusted
accordingly, resulting in a
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).
Conclusion; 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!
Significant space savings!
By transporting only the air necessary for ventilation and dehumidification purposes, RC systems significantly reduce both the volume and the velocity of air transported through buildings. Thus reducing
the space necessary for the ventilation system and its duct work. RC systems only require about 25%
of the building volume occupied by a traditional air-conditioning system.
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 height savings, the size of the risers in building core can also be significantly reduced,
increasing the rentable floor area!
In new buildings;
- at a given no. of floors, the total building height can be reduced = reduced
construction costs!
- at a given building height, the no. 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 conven
tional all air system!
Applications of Radiant Cooling?
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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.
On a first cost basis, standard Radiant Cooling systems are in a competitive price range with all air
systems (incl. mineral fiber ceiling panel system).
On a long-term basis Radiant Cooling systems offer significant benefits in terms of life cycle costs!
- lower energy costs due to higher efficiency!
- virtually no maintenance costs!
- high quality long life product!
- system can easily be reconfigured to adapt to changes in the floor plan layout!
Architectural Designs with Radiant Cooling? The Radiant Cooling systems are generally mounted on metal 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 Radiant Cooling systems are not limited to 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 an option. The panels are extremely stiff and lightweight, which allows very large spans, without the slightest deflection.
Standard office designs
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Structured or integrated designs
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Exclusive custom designs
