Numerical analysis of thermal comfort in Near-Zero Energy Buildings (NZEB) with light radiant ceilings and diffuse ventilation

Renewable energy sources for heating and cooling buildings usually have temperatures close to room temperature and therefore a limited convertibility potential, i.e. they are of low value. To exploit low-valued energy sources Low Temperature Heating and High Temperature Cooling (LTH-HTC) systems must be developed.
Hydronic radiant ceiling systems with large surfaces for heat transfer are well suited for LTH-HTC. In this paper, a suspended capillary tube ceiling placed on top of perforated gypsum ceiling panels was examined. These panels make it possible to combine a heating/cooling ceiling with diffuse ventilation, also known as leak ventilation, using larger surfaces to provide air into the room instead of diffusers.
Annual energy use in an office building was investigated in the dynamic building simulation tool IDA Indoor Climate and Energy (IDA ICE). The office building contained both offices and meeting rooms. Worst-case scenarios were investigated in the office building, considering heat gains, solar gains and the temperature offset between supply water temperature and room air temperature.
The studies were carried out to determine whether reducing the temperature offset in near-zero energy buildings (NZEB) to ±2-4 °C would be possible without reducing the thermal comfort of building occupants, and whether this would yield energy savings.
The results show that in an NZEB building it would be possible to provide adequate thermal comfort with a minimum use of energy: an energy saving of 36-41 % compared to a fan coil system running with the same temperatures was found to be possible.