Definitions of Radiant Cooling Systems
– Radiant surface: an exposed building surface including a tube or piping configuration installed within for heat exchange within a conditioned space
– Radiant surfaces may be for heating or cooling
– Sensible cooling surface: a surface designed for sensible cooling of an indoor space through heat transfer to the thermally effective surfaces from the occupants and/or indoor space by thermal radiation and natural convection
– The network of radiant surface pipes can turn the radiant surface such as floors, walls and ceilings of a conditioned space into cooled surfaces that evenly absorb sensible heat energy such as radiant energy from solar gain, people, lights and computers, in addition to convective heat transfer from the air
Principles of Radiant Cooling and Thermal Comfort
From years of adjusting thermostats, we have been conditioned to believe that air temperature alone translates to comfort, but this is not necessarily true.
We have to consider:
- Air temperature
Space’s air temperature, monitored by thermostat as “set point temperature”
- Mean radiant temperature (MRT)
Average temperature of surrounding surfaces
- Operative room temperature
Weighted average of mean radiant temperature and the conditioned space’s air temperature
The operative temperature is what we perceive on our skin in a room and what is most important to consider when specifying a radiant system.
Higher air temperature set points during the cooling season and lower set points during the heating season are possible with radiant systems.