Insulation, Radiant and Vapor Barriers - Recommendations for insulating attic

My house is an old (built in 1910) victorian house in NJ that has no insulation as far as I can tell. The attic has plank flooring but during a recent project to install ceiling lights/fans in the 2nd floor (under the attic) bedrooms, I noticed that there is no insulation at all in the attic. The floor joists are true 2"x8"s on 16" centers (bays 14" wide). I only use the attic as storage space but it is 9' tall in the ceiling so I might eventually consider converting it to living space. Also, like some other old homes I have read about on this forum, the rafters are only true 2"x4"s so I'm not sure that insulating the roof instead of the floor of the attic is much of an option.

I was planning to pull up the floor boards then install 8" of high density fiberglass insulation batts. The only problem is that the floorboards in the attic extend under 2"x4"s that run around the perimeter of the attic and the rafters are notched around these perimeter 2"x4"s. It looks like the flooring was put on before the roof was built... is this possible? I considered using a circular saw (set to the flooring depth) to cut through around the perimeter to remove the floor planks, but thought this might be a bad idea. Is anyone familiar with this type of construction/carpentry and would it be a problem to cut the flooring? Also, more generally, is it even worth it to do all this to add only 8" of insulation? I can post/send a picture is my description was not clear enough. Thanks!

Your only realistic (and best) option is to take up the attic floor by cutting around the plates or whatever framing is in the way with a sawzall or circular saw, installing R-25 fiberglass insulation with vapor barrier towards the heated side, and re-installing the attic floor you removed-or even better- put down a layer of 3/4" underlayment or CDX especially if you are planning to finish the attic space down the road.

What you could also do, which is much better than ANY fiberglass is to install cellulose instead. You can either remoe the floor boards and install a fabric barrier over the joist and blow it in or just drill holes in your floor and fill it that way. Removing the floor and putting down a fabric barrier would be your best option.

As for the vapor barrier, some people install them and some don't(on the ceiling on the floor below). The problem with trying to install a barrier now from above is that it won't be air tight so the moisture will move through anyway so it isn't worth the hassle. If your attic is ventilated, then don't worry about the barrier.

Cellulose will also give you a higher R-value, make it more air tight and is rodent/insect resistant. Its also fire resistant.