Moisture risk when air sealing rim joists in cold climates – GreenBuildingAdvisor

I’m planning to air seal and insulate my rim joists in a cold climate (Zone 5/6) and want to make sure I’m not creating a long-term moisture problem.

The house is older (1970s), currently has fiberglass batts in the rim joist bays, and no obvious signs of rot or mold. My plan is to remove the fiberglass and install either closed-cell spray foam or rigid foam sealed with spray foam around the edges.

My concern is about drying potential and trapped moisture, especially during winter when indoor humidity is higher.

How do I balance airtightness, insulation value, and moisture safety in this situation?

Is there a preferred approach for older homes where exterior conditions and bulk water control are not perfect?

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