Euromodder,
that is a reasonable cautionary note.
FWIW, the foil-single bubble layer-foil laminate I've used as a radiant heat
barrier on my Prius is going on its second season with no evidence of
damage/deterioration from under-hood temps. It is loosely draped around the
top, front and back of the ICE.
(Granted it would better serve its intended purpose it fit the ICE tightly, on all
sides and the bottom. But, I just don't have the patience or flexibility to pull
that off.
)
The laminate came from a local Lowes chain hardware store, so I doubt the
aluminum foil is special in any way.