Airborne moisture movement in occupied dwellings. A case study approach.

This paper reports the results of humidity and ventilation measurements in occupied residential buildings to study the effect of airborne moisture movement on condensation risks. The dwellings have been fitted with a cooker hood and an extractor fan (both with variable speed control) in the kitchen and an extractor fan in the bathroom. The investigation of each case-study included monitoring the temperature and humidity at four locations in the house for a number of weeks during the heating season in order to examine the water vapour cycles in each room as affected by moisture production in the space and moisture migration from adjacent rooms and outside. Detailed short time measurements have been also taken to study the effect on the humidity in one room of water produced in other rooms, and the efficiency of the variable flow-rate extract devices for the local removal of moisture before it becomes well mixed. In this way the efficiency of each ventilation device, in isolation and in combination with the others, in removing moisture from the rooms in which it is produced, has been examined as well as its effect in reducing the rate of moisture migration to the rest of the house. It has been possible to find relationships between the moisture loads in the rooms in each case-study, thus describing the effects of interzonal moisture flows in situations typical of those found in dwellings at risk of condensation.