Radiant cooling is a system where heat is removed from the air through absorption into panels or slabs. Unlike traditional systems that work to cool the air, it lowers air temperature by removing heat. The opposite of radiant cooling is radiant heating, which causes a surface to emit heat, thus warming the air around it.
Most systems of radiant cooling consist of pipes adjacent to the wall, floor, or ceiling. Water a few degrees cooler than the target air temperature runs through the pipes. The water drains away when it has been warmed by heat attracted to the surface and new, cooler water runs into the pipes. This is known as a hydronic system.
The most popular kinds of radiant cooling systems are built around either panels or building structures. The panel systems are the most expensive, but they also offer the most flexibility and efficiency. Building structure systems, also known as thermally activated building systems (TABS) are usually built around less expensive slabs and can hold temperature longer due to their mass.
Panel systems can be attached to walls, but are usually mounted on the ceiling. As they are not a part of the construction, it is usually easier to move the panels to accommodate different designs and fixtures. Though they do not have the thermal mass to hold temperature as the slabs do, they do have more flexibility in adapting to variances in external temperatures. They tend to be the best option when a highly adaptable system is needed or if the system is being added to an existing structure.
Slab radiant cooling is most commonly installed in the floor, though it can also be in the ceiling. The location of the system depends on external heat. Often, a ceiling system can be more effective because it is not covered by items such as carpets and furnishings. If there is a lot of heat bearing down on the roof, a floor system may be a more efficient choice. The less-expensive slab method is best used when the structure is being built, as it is a more integrated part of the building.
One of the primary benefits of radiant cooling systems is that they usually require less energy to cool air than traditional systems. Conventional fans take more energy to operate than pumping water through pipes. The most common drawback to using the system is excessive condensation, which can be remedied with the addition of a dehumidifier system. For this reason, radiant cooling is the least effective in areas of great humidity.