I just purchased a 101 year old Victorian and in all of those years no one has ever put any insulation in the rafters of the roof. Is there a reason why this would not be done? What is the best insulation to use?. I have looked at batts and this is what I want to use but the only R value that I can find that will fit is R19. The rood rafters are 24" on center and made out of 2 X 6. Any suggestions???

I need to clean up my attic and put new insulation. I have an old colonial house and the roof has 4 gable sides. There is one window for each gable side. My attic is 1/3 finished (paneling and carpeted). The other space is just the rafters and the insulation underneath it. The current insulation looks to be partially rip out, maybe by squirrels, and I obviously want to replace that. The space between the floor rafters is 8- 10” wide (old construction), and is covered with 2 X 8 wood beams. The wood beams make up the floor in the attic. I can easily lift the wood beams. Once I clean and disinfect I will lay the new insulation between the rafters, and underneath the wood beams. I found some dead animals and some droppings in the unfinished area. I want to cleanup, vacuum and reinstall new insulation between the floor rafters underneath the wood beams. What type of insulation is appropriate? I checked home improvement stores; it seems that the standard is 15” wide rolls. Can I use these rolls by cutting them by half? Is there functionality in the plastic where the insulation is contained? Is this plastic the vapor barrier? If so, how will it work if I cut open the insulation from the plastic? I will greatly appreciate if you can advice me on how to take care of this project in my home. Thank you for your consideration.