The 2nd floor of my 50-year old Cape varies wildly in temperature from
the 1st floor during the winter and summer months. I was investigating
ways to minimze heat loss though the attic and exterior walls/sloped
ceilings of finshed rooms on the 2nd floor.

Are far as I can tell, there is minimal insulation in the 2 side attics
which I have access to. Any that is there is about one inch thick and
is prob the original insulation. There is some additional space behind
the kneewalls of the 2nd floor. I don't have access behind the walls
but expect that there is little or no insulation. This area is maybe 3
feet deep and runs almost the enire length of the 2nd floor.

For the areas I can access, fiberglass batts seem easy enough but the
blown fiberglass contrarctor I spoke with was against using blown for
any cavities that we could not access such as behind the knee walls,
exterior walls and sloped ceiling. He was concerned with blockages
that could not be seen and any old insulation that might become a
blockage. Now I thought the whole point of blown-in was so you could
retrofit old houses and not worry about tearing down drywall/plaster.

Is cellulose a better solution in dealing with blockages?

Also would this upgrade in insulation solve my sweltering upsairs/cool
downstairs problem in the summer?

Any information would be greatly appreciated.