News wrote:

snip
I always thought the shiny side reflects, so needs to be facing where
heat needs to be reflected back and there needs to be a 1" gap between
that and any other surface. Having it under floors facing down should
not be effective. Yet I have read that some makers say it does not
matter which way it goes, I find that hard to believe.


Then you need to develop an understanding of emmissivity.

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