Not an expert but have read a bit on the subject. If you have felt under
the
siding now it may be as good as the housewrap depending on your locale.
If
you have nothing adding housewrap will offer some benefits. I don't have
a
clue as to what a $ payback might be. Comfort might be a bigger factor.

Thanks, already have tar paper so I won't bother. I think airsealing the
attic and interior walls will have a greater impact.