Deciding upon the best insulation for vintage Airstream trailers is quite a tricky task – do you go for the widely accepted approach of using foil bubble insulation, do you go more traditional rock wool, maybe sheep’s wool, or something a bit more high tech?
If you read all the marketing blurb about foil bubble insulation products, and the quite incredible R-values (the measure of heat resistivity) they have achieved in tests, it’s really a no-brainer. HOWEVER, when you delve a bit deeper into how these results were achieved, you might begin to have your doubts. As quite a few pieces of research online into these ‘miracle’ products highlight, the insulation rating is measured when the insulation layer is contained in an airtight box with a significant air gap on either side of it, which is naturally making its own significant contribution to the insulation properties achieved. In real life, and in the case of insulating a vintage trailer, the foil insulation doesn’t have such a significant air gap on both sides of it, and actually is likely to be in contact with at least one surface of the aluminium.
Unfortunately there have (to our knowledge) been no tests done on how well the insulation performs in this scenario, but since it comprises shiny, heat-reflecting foil and trapped air, it must surely be doing something to keep the heat in!
So, we’ve decided to go for that as an outer layer, but to supplement it with something which we do know works, as we’ve got coats and gloves which use it – 3M Thinsulate Sheet Insulation. Compared with a supposed R-Value of 1.5 or so for the foil insulation, a 25mm thickness of Thinsulate achieves an R-Value of around 4.5, so around three times as effective as the bubble insulation on its own. In the top photo, you can see the silver Airtek bubble insulation in situ, with the black patches being the thinsulate wadding which are glued to it; the photo below gives a better close-up of this.
A little way still to go, but once that’s all done, time to put back on the internal skin, and we’ve then hopefully got an extremely well-insulated trailer that’s going to cope with even very low temperatures, in spite of just having underfloor heating. Time will tell!!