Demand Controlled Ventilation in a Bathroom

In residential buildings moisture is adominant pollution source removed by theventilation system. The Danish buildingcode requires a minimum air change rate of0.5h-1 in residential buildings to avoidmoisture related problems. However aconstant ventilation rate results inunnecessary energy consumption duringperiods where the demand for ventilation islow and poor indoor climate during periodswhere the demand for ventilation is high.Controlling the ventilation rate by demandcan improve the energy performance of theventilation system and the indoor climate.This paper compares the indoor climateand energy consumption of a Constant AirVolume (CAV) system and a DemandControlled Ventilation (DCV) system fortwo different bathroom designs. The airchange rate of the CAV systemcorresponded to 0.5h-1. The ventilation rateof the DCV system was controlled byoccupancy and by the relative humidity inthe bathroom. The two designs differed bythe construction of the shower cubicle whichin one case was sealed and in the other caseunsealed. The construction influenced therelative humidity within the bathroomduring a shower, i.e. the pollution source theventilation rate was controlled by. Theindoor climate and the energy consumptionwere estimated based on a simplifiedcalculation of the variation of the watercontent within the bathroom during a day.The results showed that the DCV systemcontrolled by occupancy and relativehumidity had an improved energyperformance and an improved indoorclimate compared to the ventilation systemwith a constant air change rate of 0.5h-1.Moreover it was found that the bathroomwith a sealed shower cubicle reduced theperiod where the relative humidity exceeded70% by approximately half and in both theCAV and DCV system. Moreover theenergy performance of the DCV system wasslightly improved in the case with the sealedshower cubicle compared to the unsealedcubicle. The study indicated that indoorclimate and energy optimizations of DCVsystems should not be limited toconsiderations of the control system, butshould also include considerations of thedesign of the ventilated rooms.