On 28 Jul, 19:37, "dennis@home" wrote:

How does a thin foil sandwich provide many stagnant layers that are more
than 6 mm thick?

They aren't (indivudally), the overall sandwich is.

There's no need for an insulating air layer to be 6mm thick. That's
one value for a _maximum_ thickness of a stagnation layer in these
circumstances. Layers thinner than this will still have nearly as
much thermal resistance.

The overall foil sandwich is much thicker than this. It has several
layers, there are several air pockets.

As I said in the first place they don't work, they are too thin to work as
claimed.

How thin do you think these foils are, when correctly installed?