Vintage Airstream Insulation, Wiring, and Subfloor

We’ve been making steady progress on our Airstream renovation project. In the last update, we had put all of the exterior bits back on, water tested and replaced a bad piece of belly pan aluminum. I did forget to note that I moved the power inlet port, replacing it with a SmartPlug 30A connector (big upgrade from original), added an exterior cable\antenna jack, and moved the city water inlet onto the street side of the trailer from the underside.

Next comes the subfloor, wiring and insulation install. Airstreams of this vintage used pink fiberglass insulation underneath the floor – they would lay a long batt across the frame and then sandwich it between the wood and the frame member to hold it up off the belly pan. This falls into the category of “seemed like a good idea at the time.” Fiberglass insulation wicks water, is faced with a paper vapor barrier, and it just so happens that rodents absolutely love it as nesting material. Needless to say, it led to lots of problems. Their competitors, like Avion, used polyiso foam board, which is much better.

A brand new Airstream coming off the factory today uses only reflective foil insulation under the floor. This is plastic bubble wrap coated with aluminum on each side. It provides some insulation value and most of its power comes from being a radiant energy barrier – it prevents heat from passing through effectively. I wanted to go one better than this, so in addition to reflectix (the common name of that insulation), we would add batts of rock wool insulation at the same thickness as the walls – this assembly has an insulation value of about R8 or 9 and provides a radiant barrier. I did some trial and error with placement and, once satisfied, we began to put in the flooring. Each piece received a coating of TotalBoat Penetrating Epoxy, and the cut edges got a coating just before installation as well. This will help minimize any wicking of moisture into the wood as well.

To install the flooring, we start at the ends. We have chosen to do a “shell on” renovation, meaning we did not detach the upper shell from the trailer frame and separate them. Doing shell off allows you to replace the flooring in full sheets just like the factory, but it creates a lot of additional work re-attaching the two parts together, particularly if your trailer is, overall, in good repair. So for our project, we put each sheet in as two parts, and made all of the joints line up with existing trailer beams. The curves were by far the hardest part, taking a lot of trial and error to get correct. Overall it took about a week working in the evenings to get all of the floor pieces cut and installed. As I went along I re-installed the various elevator bolts that secure the frame through the floor and to the shell. I did hold out the last piece for awhile to allow easy access to the waste tanks while I was still re-installing the valves and making sure they were sealed.

After the flooring was installed the next step was making sure the interior wiring was completed. I saved all of the low-voltage (12V) wiring, which was in good repair, but replaced the 120V city power wiring, in part because we were adding several receptacles and I wanted to upgrade this wiring from regular household Romex-style wiring to “boat cable.” Boat cable is upgraded power cable made for, as the same implies, boats…which are basically always wet. Instead of solid wire, it is stranded and tinned (the copper wire is coated with tin.) This makes it much more flexible, resistant to breakage from flexing, and resistant to corrosion from moisture. Stephen helped me tear out all of the existing wiring, then I spent the better part of a week working through all of the existing wiring. This meant taking out wiring that was no longer needed, such as the tank monitoring wires (replaced by a single wire system), and relocating certain components to the new locations in our layout (ie, pump switches, light switches, etc.) I also took this time to review all of the connections in the 12V panel and, using the owner’s manual wiring diagrams, ensured everything was correctly installed. I added two solar panel ports as well – a front-mounted port for a portable system and a roof port (fed by 6 gauge wire) in the event we ever want to add panels in the future. Along with this, I installed the rear monitoring\backup camera and the antenna for the cellular booster.

With wiring all cleaned up and ready, insulation came next. I have been a big fan of rock wool\mineral wool for many years now. It is vastly superior to fiberglass insulation in basically every way and in a project like this it makes a lot of sense to use. It repels water, is fire resistant, and is rot\mold resistant. It is easier to handle and install – you can cut it with a serrated knife like a loaf of bread and it is dimensionally stable, so it will friction fit into many openings without additional tools. To install it in an Airstream, you have to cut it down – the walls are only a bit more than 1.5″ thick. So you take a standard 2×4 insulation batt (nominal thickness about 3.5 inches) and slice it in half. On the upper portions of the shell I also installed reflectix against the aluminum skin – this should act as a moderate thermal break, reducing how quickly heat from the sun transfers into the interior side.

Installing the insulation is time consuming, but really satisfying. You see a lot of real progress as you work, and overall its like putting together a puzzle to get everything to fit. On the upper portions I did have to use a light spray adhesive (similar to the factory) so the insulation would stick until the interior panels are put back in.

Next up, re-installation of the interior panels and beginning to work on all of the inside bits.

1 thought on “Vintage Airstream Insulation, Wiring, and Subfloor

  1. Pingback: Airstream Electric, Exterior Patches, Screens | The House on Rynkus Hill

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