> The reason is that insulation is actually a
> medium to isolate dead air, which is the actual insulator (air is a
> poor conducter of heat.) Therefore, given other factors, more
> effective insulation requires a thicker wall. You may, however, want
> to consider adding a vapor barrier if none presently exists. This
> would hedge against future problems.

Most "dead air"-based insulation have an R-value of 3.5-4 per inch.
However, you can enclose other gases than air, and achieve roughly
twice as good insulation value per inch. Two examples are isocyanate
and expanded polystyrene. These also work as vapor barriers.
Main difficulty would be to fit them securely inside the body
cavities, since they are (semi) rigid boards.

Note however that improvement is limited by the ratio of glass
area to insulated area in the Vanagon, unless you start covering
also the glass. Single pane glass is approx R=1. Heat "resistance"
in parallel circuits calculates just like in electrical circuits.

/Martin
--
Martin Jagersand                 email: jag@cs.rochester.edu
Computer Science Department             jag@cs.chalmers.se
University of Rochester

        Slow down and visit the VW diesel Westy page:
          WWW: http://www.cs.rochester.edu/u/jag/vw
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