Radiant cooling systems offer lower energy consumption than conventional cooling systems based on research conducted by the Lawrence Berkeley National Laboratory. Radiant cooling energy savings depend on the climate, but on average across the US savings are in the range of 30% compared to conventional systems.
These savings can be primarily attributed to:
1) Less energy required to transport heat transfer medium (water) when compared to conventional HVAC where air is used. The graphic below shows the same.
2) Chilled water supply from the chiller is typically at 16 deg C compared to 7 deg C for conventional HVAC. This also leads to additional savings.
Hot, dry climates offer the greatest advantage for radiant cooling as they have the largest proportion of cooling by way of removing sensible heat. Much of the energy savings is also attributed to the lower amount of energy required to pump water as opposed to distribute air with fans. By coupling the system with building mass, radiant cooling can shift some cooling to off-peak night time hours.
Radiant cooling also has lower first costs and lifecycle costs compared to conventional systems. Lower first costs are largely attributed to integration with structure and design elements, while lower life cycle costs result from decreased maintenance.
Because of the potential for condensate formation on the cold radiant surface (resulting in water damage, mold and the like), radiant cooling systems have not been widely applied. Condensation caused by Humidity is a limiting factor for the cooling capacity of a radiant cooling system. The surface temperature should not be equal or below the dew point temperature in the space. Some standards suggest a limit for the relative humidity in a space to 60% or 70%. An air temperature of 26°C (79°F) would mean a dew point between 17°C and 20°C (63°F and 68°F).There is, however, evidence that suggests decreasing the surface temperature to below the dew point temperature for a short period of time may not cause condensation. Also, the use of an additional system, such as a dehumidifier, can limit humidity and allow for increased cooling capacity.