"The Natural Philosopher" wrote in message
...
The very best insulator is polyisocyanurate board. Its precisely twice
as good as polystyrene and costs about 4 times as much.

Not quite. The best insulator is a vacuum. It's just nobody has found a
way of encasing a building in it yet, though I'm sure Doctor Dickhead/IMM
will detail some place where it's been done.