Both wood and straw can rot if wall moisture content rises above about 70% for extended periods of time. New information from Canada and the U.S. strongly suggests that all superinsulated homes (of which strawbale homes are only one type) must be designed to avoid moisture buildup or rotting can occur.
Some data on the degradation of wood even suggest that our past and current understanding of the dynamics of moisture and vapor barriers is incomplete, and that many newer homes with standard insulation levels which employ moisture barriers are at risk due to inappropriate installation of the barriers.
Professional straw bale builders are more knowledgeable about both the dangers of moisture and are more familiar the technques of moisture control than most builders of conventional homes. The final word regarding moisture is that it is a design problem that is shared by both timber and straw, and that buildings utilizing strawbale walls are no more prone to moisture degradation than houses built of timber.