Radiant cooling

Performance cooling

A radiant cooling system works differently according to the surface on which it is located. A cold floor transfers heat primarily by radiation with other surfaces, because the capacity for convective transfer with the air is limited. Conversely, with a radiant ceiling system, the capacity for heat exchange with the air is much greater thanks to the higher coefficient of convective transfer of a cold surface which exchanges downwards. Add to this the fact that the presence of people, computers or electrical appliances in the room creates an upwards movement of hot air and the overall effect is an increase in output exchanged by the ceiling.

A radiant wall system works in a similar way both when heating and cooling due to the the convective coefficient being the same for both conditions. In general, a radiant floor system is sized in heating mode, as described by UNI EN 1264 and later on. According to that reported in Part 5 of UNI EN 1264, it is possible to evaluate power in cooling mode using a formula. Once familiar with the winter performance of a floor-installed radiant system, it is possible to estimate the performance of the same system if it were installed on a wall or ceiling (when heating and cooling) thanks again to Part 5 of UNI EN 1264. Alternatively, a radiant system‘s performance can be evaluated using numerical simulations, as set out in UNI EN 15377-1:2008. Since a radiant ceiling system‘s performance is also affected by the presence of people, computers and electrical equipment, it is advisable to evaluate the performance of a radiant ceiling in a laboratory simulating a room environment. The regulations UNI EN 14240:2005 require the performance of a radiant ceiling system to be checked once installed in a room where heat loss to the outside can be controlled.

The ceiling must be able to remove the heat flow from various load simulators (simulating people or electrical appliances) positioned on the floor. When a condition of equilibrium is reached, the flow rate, water temperature, air temperature and temperature of the globe probe are recorded. The result is expressed by the characteristic curve of the ceiling, through which the cooling power can be estimated for each temperature difference between the water and the room. Evaluating the performance in accordance with EN 14240 in a laboratory ensures accurate results, as laboratories necessarily have to limit measurement uncertainties in order to be able to issue the certificate.

Just a few laboratories, located in Germany, are able to perform this test. The WSPLab in Stuttgart, where Eurotherm has tested its products, is one such laboratory.

Characteristic curve of the Leonardo ceiling system tested at the WSPLab