Mac, I was able to correspond with Wiggy's today. Yes, Ice will form on the outermost contact layer. The insulating material is hydrophobic and will wick moisture to the contact layer vs. collecting ice in the loft itself. So basically the insulation remains at full usefullness. Icing OUTSIDE isn't that bad, since you are basically creating a seal, much as farmers will deliberately irrigate crops for a quick freeze during low temperatures. So, there it is; a vapor liner for units that do not wick liquid and the warm sauna effect or the Wiggy system which relies on a dry environment. Either system is vastly superior to the old canvas and blanket bedroll I had to crowbar my way out of in a freeze ;^)