This project is the conclusion of a study begun in 1982 to investigate some aspects of the development and collection of moisture in exterior walls. The purpose of this project is to monitor the behavior of the test walls through their dry-out of moisture collected during the winter of 1982-83. These walls had been installed in the exterior wall of the materials testing laboratory at Forintek's Eastern Laboratory. The test walls which have been included in this study consist of variations on conventional walls, some of which have had particular problems in electrically heated houses in Newfoundland and other areas. The main research goal in this study has been to demonstrate the effect of minimizing air exfiltration into walls. The indoor environmental conditions are reasonably severe while the exterior conditions have the advantage of being produced by natural conditions. The benefits of this study are that a better understanding of the causes and cures to the problems will be attained. It may be possible to subbest how the problems may be avoided in future construction, and how they may be corrected in already-built housing. It may also be possible to help some building products recover and maintain markets for their use. One such product is hardboard siding which has suffered much criticism and loss of acceptability for reasons that are probably not related to the product or to the way it was used.