Combining suspended radiant ceiling with diffuse ventilation – Numerical performance analysis of low-energy office space in a temperate climate

The development of low energy buildings present new opportunities to develop HVAC products that works well with renewable energy sources. In this paper, we present a novel comfort system that combines a full radiant ceiling with diffuse ventilation into one flexible ceiling solution, HVACeiling. The purpose of the paper is to investigate how the combination changes heating and cooling performance and how the thermal storage cycle of the exposed slab in the closed plenum affects energy consumption and thermal comfort. The heating and cooling performance was investigated numerically in IDA ICE with daily based occurrence temperatures and compared to a reference with a radiant ceiling and mixing ventilation. The HVACeiling was a perforated gypsum board with pipes embedded that is used for diffuse ventilation and acoustical absorption as well as a radiant ceiling. Water was circulated day and night at fixed supply temperatures of 20–22 °C without any other controls. The convective surface heat transfer coefficients of the plenum was modelled in a preliminary CFD study and compared to literature and experiments. It was found that for daily based occurrence scenarios, with outdoor temperature in the range 23–28 °C, the heat exchange from the ceiling was increased 5–16% compared to the reference. The studies also disclosed improved thermal comfort, up to 1.5 °C lower peak operative temperature in the occupied zone down from 27.2 °C. This implies that thermal comfort is easier achievable with the HVACeiling, even with a small temperature offset that is well suited for renewable sources.