Monitoring indoor relative humidity fluctuations associated with intermittent operation of air conditioners.

In residential buildings, air-conditioners are usually operated in intermittent mode. Thisintermittent mode may complicate many aspects of indoor environments. Indoor humidityexcess is a major problem, since humidity excess is associated with biological pollution andformaldehyde emission. This paper reports our monitoring of indoor air temperature andrelative humidity in a real life building in the hot humid Hong Kong climate. These monitoredresults indicate that, in residential buildings, occupants habits in using windows for naturalventilation exacerbate indoor relative humidity excess. The outdoor air moisture is the majormoisture source, and when this air encounters the pre-cooled thermal masses within thebuilding at off-hours, indoor relative humidity is raised. For residential buildings, a constantventilation rate at the on-time of air-conditioner is desirable, while it is not desirable to havehigh natural ventilation rate at off-time. These monitoring results also validated oursimulation results reported in an earlier publication.