The wall of an Airstream is composed of an exterior shell, the ribs that form the "frame" of the shell that keeps it in shape, the interior skins, and the insulation that lives between the interior skin and the exterior shell. The interior skins are made of aluminum, just like the exterior shell.
The new Airstreams often have shiny interior walls, and the look has become so popular that many people with vintage Airstreams either replace their interior skins with new, shiny aluminum panels, or strip off whatever paint, vinyl, or material is on them so that they are shiny. Nobody removes their interior skins permanently so that the inside of the exterior shell is permanently visible. With no insulation in an AS wall, the trailer is not inhabitable--believe me, I used mine as an "aluminum tent" a few times last fall. The walls are only ~1.5" thick, and there is a running debate what insulation is "best," but I can promise you that no insulation at all is not the way anyone would willingly go.
So, with insulation in the walls, and the interior shiny skins in place, you may see slightly more heat transfer than you would with a vinyl layer, or a layer of paint on the inside, but it would probably not be measureable. The biggest problems reported by most people who retro-fit interior shiny aluminum is that it is uncoated, so every finger print becomes a blemish and has to be rubbed out. The factory uses a plasticoated aluminum sheet for their interiors (and it its obscenely expensive)