7.3 Vented Enclosed Exposures

Examples of vented enclosed exposures are attics, which must be vented to release excess heat and moisture, and rafter and floor cavities if vents are installed.

Corrosion of metal connectors and fasteners in vented enclosed exposures depends on the location of the metal connectors in the enclosed space. Corrosion rates near vents, where outside airflow is concentrated, are often similar to the rates in partially sheltered exterior exposures (see Section 7.1). Corrosion rates for metal connectors that are not near vents or that are covered by insulation are expected to be much lower.

Some vented enclosed areas can be hard to access, complicating inspections to evaluate the condition of the metal connectors and replace them when needed. In these locations, it is worth considering a more corrosion-resistant metal connector since its condition will rarely be evaluated.