Air is the best insulation,, but, it has to be not moving.
Insulating material that fills the gap between the pot and outer layer should be as "fluffy" as possible.
If you compress the insulating material too much, all the air is compressed out,
that causes the insulating material to return to being a "conductive material".
So, you want loose, to insulate well, but, you also do not want the insulating material to fall off,,
so, you get to decide,, how tight should it be? ~ `