Checking the insulation on a second hand conversion

[radfraz]

I'm looking at a second hand build. What's the easiest way to check how well the vehicle has been insulated?

 

[nomislotsirb]

I'm sure others will provide a more comprehensive answer, but as a starter for 10 I'd tap on the panels from the outside which would give an indication as to whether acoustic insulation has been added. Thermal insulation is possibly harder to identify without removal of a panel.