re: Attic Insulation Questions

The theory behind it is that closed cell is impermeable, therefore if a roof leak occurs it will collect between the roof deck and insulation and rot the roof deck without you ever knowing.

Open cell is more water permeable and will at least show a waterspot in the event of a roof leak. That waterspot may show up "down stream" and not at the actual leak, but at least you know something is wrong.

Also, closed cell is a much harder product and will be a mess if you have to replace any roof decking. Open cell is a softer product and easier to remove in that situation.

Lastly, your homeowners insurance may not cover you in that scenario above with the closed cell. Just a thought. I am not an insurance agent, just giving my opinion.

ETA: I agree with the above comments about sealing your walls and eaves. You need to treat that attic as part of your house to prevent a domino affect of issues ranging from humidity, mold, inefficient HVAC