When i have took out all of the interior and capret ther is a sort of "underlay" beneath the carpet.

Most of this has came off dry and in 1 piece, however underneath where the dash is, it has all just snapped off and was pretty wet and soggy.

I know this isn't a good sign, but im getting the cars floor all sorted out within 2 weeks, welding etc.

What could i use as a replacement for this material under the carpet, is is more of a heat insulater or a sound proofer...