According to :
The contractor said the cost difference between R38 and R30 is minimal
compare to the cost of the job, so I am just going to go max and
install R38.

Ask your contractor if he can do rockwool (eg: Roxul).

Generally it's the same price as fiberglass, but is slightly
superior in all respects. Particularly that it's a lot less
picky and less likely to blow around. Can be blown or used as batts.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.