I have a question regarding the best way to insulate an 80 year old house. I live on Cape Cod, Masachusetts. The house was built w/ balloon construction. The interior walls are plaster w/ wooden lath. I plan on replacing the windows and reshingling and installing Tyvec. Do I need to install blocking at the bottom of each bay before blowing insulation in. Do I need blocking at the top of the partition in the attic also (to act as a fire block)? Thanks for any help/ suggestions.