Usually it means between the insulation and the interior space. For
example, if you remove the front door panels you'll find a clear (or it
once was clear) plastic sheet under the door panel and on top of the
metal frame. Insulation would go in between the interior metal frame
and the outside metal panel.

In house construction it is assumed that the insulation area can breath
to the outside (and hence allow the water vapor escape. In vehicles,
the metal panels tend to prevent water vapor from escaping...unless
there are drip holes at the bottom or some other place that allows for
passage of water or water vapor.

On vehicle doors, there are usually drip holes at the bottom seam (and
outside the weather stripping). Those big side panels on our Vanagons
don't have drip holes, which means that water that gets in there can't
readily escape...and hence it causes rust.

On Monday, August 25, 2003, at 12:16  PM, Tim Demarest wrote:

> For those of us considering similar work on their vans, can you define
> "on top of"?
>
> Does it mean:
>
>         - between the insulation and the body sheet metal.
>         - between the insulation and the interior space.
>         - both.