We are enclosing a pre-existing carport and have laid the floor, hung drywall, etc. However, there are gaps (up to 3/4" at some places) between the pre-existing plywood ceiling and the new drywall. My question is how "should" these areas be sealed? Can the crown molding that we are installing be used to seal these gaps or is crown simply for decorative "cosmetic" purposes?

There are also gaps (up to 1/2" at some places) between the sub-floor and walls. Will the pergo type floor being laid on top of the sub-floor, as well as the floor board trim be enough to "seal" these gaps?

If we use the crown molding and floor boards to seal these, should we first caulk or use the foam to fill the gap in? My concern is both energy efficiency as well as pest intrusion.

Thank you for any assistance/guidance you can provide.
MP1