https://www.bobvila.com/articles/expanding-foam-insulation/
Great Stuff Fireblock for a quick solution. Not the cheapest but will keep the pests out and might still be technically within code.
Home Improvement
https://www.bobvila.com/articles/expanding-foam-insulation/
Great Stuff Fireblock for a quick solution. Not the cheapest but will keep the pests out and might still be technically within code.