I live in a 2 story home that I purchased about 5 years ago in Florida that was built about 15 years ago. I was recently in the attic area and noticed it has blown in insulation that has settled to about 4 to 5 inches thick, not much higher than the 2X4 trusses. Would it be worth the investment to blow in another 10" on top of existing insulation? What should the minimum thickness be?