Abstract
The aim of this research is to understand how radiant cooling technology, new to many building designers in North America, work to maintain indoor comfort issues. Radiant cooling works differently than all air cooling system. All air system removes heat load instantaneously while radiant cooling operates in a time delay manner. In a radiant cooled building, the latent load cannot be removed via radiant panels or thermally activated structures. A separate cooling piece of equipment has to be added in order to mitigate indoor humidity. In the newly constructed SMUD office building, East Campus Operations Center (ECOC), ceiling radiant cooling and active chilled beam technology were used to achieve the zero-net certification. Yet, operators experienced elevated humidity levels during the hot summer days, with little leverage to remedy the problem. The direct outside air system (DOAS) and chillers could not bring down the indoor dew point. When the building dew point approached 60 °F occupants complained. Facility operators could not lower the chilled water temperature below 53 °F in the air handler cooling coils and at some days it was even higher. The problem at hand was the DOAS ventilation loop and the building radiant loop were not decoupled. Thus, the central plant could not provide dedicated chilled water temperature. It was discovered with TRACE 3D Plus simulation software that cooling equipment for the office building was undersized so the chilled water temperature could not be lowered to desired lower temperature setpoints. The actual energy use data provided by SMUD confirmed that the building consumed more energy than initially designed. The TRACE 3D Plus model energy output, which was modeled per the Energy Modeling Report, and SMUD actual energy use data was within two percent margin of error.