Hydronic-based radiant systems have verified advantages over air systems, such as the improved transport efficiency of using water instead of air as the thermal distribution fluid, improved plant side equipment efficiency with warmer cold water temperatures, and, particularly with TABS, the possibility of night precooling using cooling towers. Higher peak design cooling loads, however, is not the same as higher overall energy consumption. This finding has important implications for the proper design and sizing of radiant systems along with the required reduced-sized air distribution system (for ventilation, control of latent loads, and supplemental cooling). In this article, we present recent research evidence that sensible zone cooling loads for radiant systems are different (in fact, are often higher) than cooling loads for traditional air systems. There are three primary types of water-based radiant systems: (1) for new construction: plastic tubing (e.g., PEX) embedded in the structural slabs, often referred to as thermally activated building system (TABS) (2) for retrofit or new construction: suspended metal ceiling panels with copper tubing attached to the top surface (radiant ceiling panel, RCP) and (3) for retrofit or new construction: prefabricated or installed-in-place systems consisting of embedded tubing (e.g., PEX, or small, closely spaced plastic tubing "mats") in thinner layers (e.g., topping slab, gypsum board, or plaster) that are isolated (insulated) from the building structure (embedded surface system, ESS). However, it is difficult to find detailed standardized guidelines for calculating cooling loads for radiant cooling systems, which is the subject of this article.Ī radiant system is a sensible cooling and heating system that provides more than 50% of the total heat flux by thermal radiation. (7) A database of representative buildings with radiant systems can be found at. (3,4) Several case study examples with design information have been reported for an airport, (5) large retail store with floor cooling, (6) and other thermally active floor systems. (1,2) Olesen and others have discussed the principles of designing radiant slab cooling systems, including load shifting, the use of operative temperature for comfort control, and cooling capacity. Interest and growth in radiant cooling and heating systems have increased in recent years because they have been shown to be energy efficient in comparison to all-air distribution systems.
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