I just modified my attic scuttle, which is now framed between three joists. However, I've got a small gap in the middle joist that's about 6 inches by 3 feet and lacks insulation. What would be the best way to insulate these gaps? Should I cut up a fiberglass batt, use spray foam for the whole area, or create some solid foam pieces to fit?
2 Answers
I'd recommend going with spray foam for those gaps. It'll provide some extra rigidity to the joists and seal up any drafts effectively.
If you can get to it easily, consider using mineral wool insulation instead of fiberglass. Fiberglass can absorb moisture, sag over time, and isn't as good against pests. While spray foam is an option, I’d be cautious since it can sometimes trap moisture and lead to mold issues if it delaminates.