"dnoyeB"

I agree. Its what makes gas 'gas'. That it moves around so freely. I
can assume Argon has lower specific heat than average air. Which means
it holds less heat.

Heat is transferred by conduction and convection (in this case). Perhaps
argon is better on both counts, but it would be nice if the whole mechanism
was translated into R values, so you'd know what it costs for an additional
R unit.

In addition, I wonder how long the gas stays trapped between the two sheets
of glass. And how do you know when it escapes.

It all adds up to a bit of hocus-pocus, for a price.

Rich