What these guys already said is good information......just going to add, I helped a few people blow in insulation in the attics. In our region they say you need r49-60 so r60 is around 18-20 inches with little or no base......just helped someone 3 weeks ago with cold drafty house with 3000 dollar propane bill a year. I blew in 48 bags in a 1700sq ft home, you need 3 people..... 2 to feed and 1 on top, about 20 bags an hour we put down....for a total cost of around 380.00 and she said already can feel huge difference in closets and back bedrooms with the cold drafty feel and furnace isn't running as much! you can use a temp guns to measure the walls when its cold out to pin point uninsulated area in the walls.....hope this helps