Radiant Heating and Cooling: Questions? . . . and Answers!

• How does radiant heating and cooling work?
  A radiant ceiling panel is used. It is placed behind the ceiling drywall, plaster or paneling. Warmed water circulates through panel piping in the ceiling, radiating warmth to the space for heating, and cool water circulates through the same panel in the ceiling, absorbing heat from the space for cooling.
  

• What Equipment is used to heat and cool the building?
  The most common arrangement is to use a dual function packaged boiler for heating and domestic hot water production. A packaged chiller is used to chill the water for cooling. In some cases it makes sense to use a reversing air source chiller.
  
  
• Can I use a geothermal heat pump to heat and cool my radiant building?
  Yes. Geothermal heat pump systems work very well with radiant panel heating and cooling systems. The low temperature heating and high temperature cooling design of the radiant panel system helps the geothermal heat pump to operate efficiently. 
  
  
• Is a radiant heating and cooling system efficient?
  A radiant heating and cooling system can be more efficient than a forced air system;

1. The mechanical equipment is very similar, but it costs less to operate a pump than of a  blower motor to distribute the energy throughout the building.
2. Back losses from the radiant panel are generally less than duct losses.
3. The mechanical equipment operates more efficiently
   and building envelope losses can be lower because:
          a.  radiant heated rooms can be comfortable at a lower temperature.
          b.  radiant cooled rooms may be comfortable at a higher temperature.
4. A well designed radiant panel system can use less energy than a forced air system for the same space.
5. However some will people operate their home for optimum comfort, therefore the operating costs may similar..
6. A badly designed radiant system can use more energy than a well designed forced air system.
   

• Are radiant ceiling panels only for new construction?
  Radiant heating and cooling can be installed in new construction or retrofitted into existing buildings. In some cases it may easier to condition an existing building with a radiant heating and cooling system rather than a ducted forced air system. In most cases the ceiling is not a decorative element in the building design. For new construction the ceiling is lowered 5/8" and in a retrofit, the ceiling is lowered a 1 1/8" and sheet rocked. The architectural impact on the building design is minimal in most cases. 
  
  
• Do radiant ceiling panels need to be horizontal?
  Radiant ceiling panels can follow any ceiling contour the building designer desires. Radiant heat (and cold) travels in straight lines at the speed of light. An object which cannot "see" , or is "shaded" from the radiant panel will be cooler in the heating season (and warmer in the cooling season) than objects in line of sight of the radiant panel. For instance a canopy on a four poster bed would shade anyone sleeping on the bed from radiant heating (or cooling). 
  
  
• Is radiant conditioning more comfortable than a forced air system?
  Most people are more comfortable in a radiant conditioned space. There are no drafts in a radiant system. There is no noise from a properly designed radiant system. Heating and cooling system design and individual preference can make a big difference in perceived comfort. 
  
  
• Is a radiant ceiling conditioned building responsive?
  A radiant ceiling conditioned building responds very quickly to thermostat inputs and begins to achieve comfort in a few minutes. There is not much need to anticipate occupancy, to pre-condition a building before it is to be used. This is not true for a radiant slab building where it may take several hours to achieve comfort. An air conditioned building may take 30 minutes or more to reach comfort depending on the difference at the start of the pre-conditioning cycle. 
  
  
• Is heating from the ceiling uncomfortable?
  Heating from the ceiling resembles the way the sun heats the earth. However the ceiling surface temperature is barely warm, and the furniture and other surfaces approach the ceiling temperature in a few minutes. If you notice that the ceiling is uncomfortably warm, then the supply water temperature is too high, and should be set a little lower. This lower temperature will result in a longer on cycle and fewer starts for the boiler, resulting in greater economy as well as greater comfort. I heard from a bald man that his scalp can get chapped in a ceiling heated room.
  
  
• Is Humidity a problem?
  It all depends on your location. Radiant panel systems shall never be operated to dehumidify the indoor air. In a hot humid climate, a forced air dehumidification system will be required. In a hot dry climate dehumidification will not be required. In moderate humidity climates, controlled ventilation, or mechanical dehumidification will be used. 
  
  
• What about mold?
  Mold grows in damp locations. Dampness is created when water leaks or condenses on surfaces. Condensation is a concern in radiant cooling systems. Cooling system design and controls prevent operating conditions which produce condensation. Mold problems will be the same as or less than in traditional air conditioned buildings. A properly designed and operated radiant panel cooling system will not promote mold growth. 
  
  
• How will I know that my radiant heating and cooling system is working?
  Radiant heating and cooling systems are silent, and do not create drafts. You might be able to hear the boiler or chiller if you listen closely, but they not in the inhabited space and operate intermittently. The best way to understand it is, if you are not uncomfortable, it is working.