Something I always thought of using is Dupont Tyvek.
It's a high performance vapor barrier for homes, installs under the
sheathing.
Suppose to let moisture out of the walls but keeps water from entering.  So
it breathes but doesn't leak.  It's also very durable.  Some mailing
envelopes are made of this stuff, doesn't rip or tear.
Installs with a regular looking tape available at lowes/home depot etc.

I'm gonna try it next time the need arises.

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David Beierl
Sent: Thursday, April 08, 2010 1:57 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Was: Stereo Upgrade Project Now: Vapor Barrier

At 01:27 PM 4/8/2010, Peter DiFalco wrote:
>So... what should I use as a vapor barrier? Any online sources for that?

The original is polyethylene film, I'm guessing ten mil.  Regular
household Saran Wrap is the best easy-to-hand vapor barrier I know,
much better than polyethylene for equal thickness.  That and tinfoil,
which is harder to handle but a perfect barrier.

Yours,
David