Hi Anna
Hi Anna
Yes, take the existing boards off. Keep to one side.
It’s fine to glue (spray adhesive or liquid contact adhesive) the Kingspan to the van walls.
Fill the smaller gaps with recycled plastic insulation, which is like rockwool, but safe to breath around.
Then refit the ply boarding.
This is assuming that your existing boarding is good quality and fits well.
When you stick the carpet on, any gaps or poor fitting boards might be visible.
So make sure the boards fit really well, or fill the gaps in before carpeting.