The infiltration component of ventilation in New Zealand houses.

The air infiltration component of house ventilation is calculated and discussed in relation to winter space heat losses and rneasures necessary to control moisture. The airtightness of 80 houses sampled from three major urban areas was inspected for association with location, external cladding materials, and design features such as the shape and complexity of the building envelope. A useful correlation of airtightness with envelope complexity emerged which gives a coarse but useful way of forecasting airtightness from building design information. Winter season infiltration rates were calculated using hourly weather records, airtightness and wind exposure data and the Lawrence Berkeley Laboratory infiltration model. These infiltration rates represent the minimum ventilation rate currently achieved in New Zealand houses and are used in a discussion of the value of further improving house airtightness. Finally, results of surveying moisture problems in houses of known tightness are used to help establish the respective roles of ventilation and space heating in the control of indoor moisture in a temperate climate.