In this question, I asked about the best type of insulation to use on a hinged metal attic door, when one is also concerned about heat entering around the edges of the door when closed.
The answer I received is a good one (and provides an answer to that question as it was asked), but adds an extra step to entering the attic. If I may, I would also like to ask the separate question of when one is not concerned about the edges of the door, but just concerned about the lack of insulation of the door itself. So...
What is the best type of insulation to use on a hinged metal attic door (no integrated ladder)?
Only concerned about heat entry through the door when closed.
Would like something that does not cause a mess when the door is opened, and does not add extra steps to entering the attic. I'm thinking along the lines of something added to the metal door itself. There are a number of choices, and I'm wondering what type of product is best.