A typical home air conditioning system will have a number of sources of wasted energy: air leaks out of the ducts, wasting the energy used to cool it, and the fan used to circulate the air round the house not only uses a lot of energy, but adds that energy to the air it is circulating.


A radiant cooling system works by circulating chilled water through pipes embedded behind the ceiling, walls, or floor of the house. This keeps the surfaces of the room cool, so excess heat in the room can be absorbed by them and removed. Because of the high heat capacity of water compared to air, less of it needs to be pumped round thereby saving energy. Because water will not leak out of the pipes the way air leaks from the ducts, less energy is wasted.


Radiant cooling systems also benefit from the fact that human comfort depends not just on air temperature but also on radiant temperature – think of the difference between standing in direct sunlight or in the shade. A radiantly cooled room with cool surfaces allows the occupants to stay comfortable at higher air temperatures than in a conventionally cooled room. This means the thermostat can be set to a higher temperature, giving further energy savings.


One of the reasons why very few residences are radiantly cooled is that, in order to avoid condensation, the surfaces have to be kept at a reasonable temperature meaning that a larger area needs to be cooled. This adds to the cost which has meant that, energy savings notwithstanding, conventional radiant systems are not cost competitive.


We are running a project to design a radiant cooling system based on a modular system of chilled panels. By creating a standard-sized panel, fabricating them in bulk should lead to cost savings. The WCEC will be testing radiant systems to answer these questions:


  • Are radiant systems as reliable as standard, forced-air systems?
  • Can we create new fabrication methods/use new materials to make radiant systems closer in cost to conventional forced-air systems?
  • Can phase-change materials help reduce the overall volume needed to pump through a hydronic system? Can they help reduce the volume of a hydronic storage tank?