The need for reduced energy consumption has led to an overall decrease of air infiltration rates in buildings. particularly in dwellings. Unfortunately. this has given rise to a significant number of problems involving condensation. with resulting damage to the structure and contents of affected buildings. Various means of condensation control are available. The use of a passive ventilation system to achieve this aim has several attractions. not the least of which is that the occupants of houses fitted with such a system need little. if any, knowledge of the principles involved. or instruction in its use. to derive maximum benefit. This paper describes a program of work which compares the performance of a passive ventilation system, installed in the kitchen and bathroom of a house of timber framed construction. in comparison with the use of mechanical extraction, window head ventilators. and opening of windows, as alternative means of ventilation. Particular emphasis is placed upon the influences of wind speed and wind direction. Using the ventilation rate measurements in conjunction with dry and wet bulb temperature data. rates of moisture extraction due to the four different means of ventilation are calculated, and the effects upon condensation risks are assessed in the light of predicted minimum ventilation rates required to avoid condensation. Comparison of predicted minimum and measured ventilation rates leads to the estimation of the effect of each type of ventilation upon space heating energy consumption.