Somehow, I doubt it.

The whole point of insulation is to keep the warmth of your body near you. Air isn't the greatest of insulating mediums, since there's problems with radiant heat loss, right, and convection too if you talk about air moving within the garmet. Instead, by wearing clothes of different varieties, we keep the air around us "trapped" and thus slow the rate of heat lost to the environment. I can't envision how changing one gas (ie, air around our body) and wrapping it in another gas (in this case, argon) would help. I wonder if, instead, the jacket material is trapping the heat the same way a plastic bag would.

After all, think about a mountain top, say something in the Rockies. You'd think that being 10'000 feet up, you'd be 2 miles closer to the sun, and a bit warmer, right? Yeah, not happening.