Problems and questions for predicting comfort conditions in a zero energy residential building

Reducing buildings energy demand has been recently the main issue for researchers and companies, trying to develop strategies towards Zero Energy Buildings (ZEB) and Plus Energy Buildings (PEB). However, the higher envelope insulation applied to reduce the heating energy need led to rise HVAC systems efficiency to provide proper Indoor Air Quality (IAQ) in summer periods, whose management strategies may affect comfort if the operating conditions are not properly set. The most efficient system in cooling season should provide cool and dry air, which will be supplied by mechanical ventilation via a cold coil. However, in order to belong to the highest IAQ category according to the standard EN 16798, high air flow rates are needed, which may induce to undesired undercooling when the air is cooled and dehumidified. These issues have been widely investigated in literature, while less research focused on the clothing resistance change according to the time of the day over the year. In the case study presented, the mechanical ventilation is coupled with radiant heating and cooling ceilings. Questions related to strategies to guarantee thermal comfort along the whole year are investigated. Different combinations of control strategies and clothing conditions are considered to set the most suitable dynamic simulation for a residential ZEB or PEB. The results obtained are relevant for experts to properly define dynamic calculations and systems’ operating strategies.