Two possibilities
Foam board glued to the door panels
or fiberglass bats held in place by Vinyl ( e.g. garbage bags and staples.

"SamL" wrote in message
...
We have a finished attic. Typical kind, I think, side walls slope down to
about 3-4 feet from the floor, then become vertical.

Behind the vertical part of the walls is storage space. There is a door on
each wall giving access to that space. The walls have fiberglass
insulation on them, but the doors don't.

Since the door feel noticably warmer than the walls on a hot day, I'd like
to put some insulation on the door. Any suggestions on how I might attach
the insulation?

Thanks,

Sam