I have rock wool insulation stapled to the rafters of my cape cod
built in 1952. It's in pretty good shape but I'm not sure if it should
be replaced or augmented. My 2nd floor is always a degree or two
colder than my 1st floor in the winter so I decided I'm in need of
some insulation. I checked and noticed that where the dormers were
added there is a lack of insulation. A handyman I had doing other work
on my house said that the wool insulation is better than the
fiberglass and I should keep it and just add some insulation to the
knee joints near the dormers where it is lacking and that should be
enough. I'd like to take care of this correctly so I'm wondering what
the conventional wisdom of rock wool insulation is. Is there an R
value for it?