... from the website of the Vinyl Siding Institute.   Reactions?
Posted by Christopher Gray

9. Allegation: Vinyl siding causes moisture and rot.

Response: Vinyl siding does not cause moisture damage. Moisture from the
inside is caused by inadequate ventilation and should be addressed by a
qualified engineer. Insofar as moisture from the outside is concerned, vinyl
siding systems are designed to allow for ventilation behind the siding and
experience has shown that the design is effective. Weepholes are punched at
intervals along the bottom butt edge of the siding to allow any condensation
to drain out. The locks and lap joints in conjunction with the open ends of
the siding, although hidden from view in J-channel or corner posts, still
allow for the dissipation of water vapor from behind the siding to the
outside. If moisture is presently being trapped in the walls of the
structure, obviously the installation of vinyl siding will not cure the
problem. However, it will not make it worse. Painting the old wood siding is
not an answer. In fact, a couple of coats of oil paint make an excellent
vapor barrier. That is why blistering is so often observed on painted clap
board - the moisture is trapped behind the paint.
END