Knowledgebase
Occupancy gains not as expected in EnergyPlus simulations
Posted by Andy Tindale on 28-Sep-10 07:30 AM

In some cooling design and simulation results you may find that occupancy sensible gains are much lower than expected. This occurs during times when the internal temperature is very high. The reason for this is outlined below.

DesignBuilder supplies EnergyPlus with number of occupants, the occupancy schedule and the metabolic rate gain for the activity (data supplied in Activity model data). The metabolic rate determines the total heat gain per person in the zone under design conditions. The sensible/latent split of the occupancy gain to the space is based on a correlation to account for variations in space temperature and humidity levels. At temperatures much above 30degC, the latent component can start to dominate and and at even higher temperatures the sensible gain reduces to almost zero as most of the metabolic gain is dissipated through latent heat. In everyday terms, humans cool themselves entirely through sweating as the ambient air temperature rises towards the internal body temperature (37degC).