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The intent of this brief is to provide code-related information about controlling moisture in unvented attics by installing a vapor diffusion port/vent that would convey water vapor from an unvented attic to the outside when air-permeable insulation materials are installed and can be verified as being in compliance with the related codes and standards for residential construction. Providing consistent information to document compliance with codes and standards to all relevant parties responsible for verifying compliance (e.g., code officials, builders, contractors, designers, etc.) is expected to result in increased compliance and more timely, less challenging and more uniform plan review and field inspections.

The intent of this brief is to provide code-related information about sealing and insulating existing vented attics to help ensure that the measure will be accepted as being in compliance with the code. Providing the same information to all interested parties (e.g., code officials, builders, contractors, designers, etc.) is expected to result in increased compliance and fewer innovations being questioned at the time of plan review and/or field inspection.

From a model code perspective, submittal of construction documentation, permitting, plan review, and field inspection may be required depending upon the specific details of renovating the floor above an unconditioned space (e.g., floor over a vented crawl space). Several different approaches can be taken to seal and insulate existing floors during a renovation project.