I recently discovered that our garage ceiling has no insulation in it. The house is a raised ranch with three bedrooms and two bathrooms above it. Although the garage has a register for heat(no return), at best it is kept to 50 -55 F in the winter. That end of the house is always hot in summer, colder in winter. I am sure insulating is a good idea, but it is a finished ceiling over the garage (5/8 in. drywall). The question is do you blow-in insulation and hope for adequate coverage, or do you rip out the drywall and insulate with fiberglass bats, then replacing the drywall?