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.

4 thoughts on “Vintage Airstream Insulation, Wiring, and Subfloor

  1. Renita

    hi there,

    I’m so happy to have found the instructions and pictures of how you insulated your subfloor. I have a few questions for you if you don’t mind.

    1) What is the exact kind of Reflectix did you use for your subfloor? There’s so many different products in their website.
    2) Also, what type of adhesive spray did you use laying the Reflectix on the metal joist? I will be using marine grade plywood instead of applying the epoxy of the regular plywood.
    3) For your insulation, you used the rock wool all over correct?
    I’ll be using that for the floors just like you did.
    4) For the ceiling and walls, I’ve already ordered Havelock wool. what type of adhesive did you spray on the ceiling to help keep the wool in place?
    5) Did you use the same Reflectix on your ceiling and walls? If so, did you use the same adhesive as you did on the joist?

    Thank you in advance.

    1. Douglas Camin Post author

      Renita –

      Sure, no problem.
      1. We used this Reflectix:
      2. I bought some stuff off the shelf at my local hardware store. It was IPG AC50 Spray Adhesive. It’s just what they stocked, it wasn’t something special. 3M makes one that is commonly available and would work well.
      3. Yes – we use 2×4 sized batts and cut them in half, which is roughly the correct size for the bays. This one specifically:
      4. Wool I bet is going to be real nice – it has qualifies similar to the rock wool. I used the same adhesive in the places. On the sides it often friction fit, but as you move up to the overhead you need to glue it. So the reflectix is glued up and then the mineral wool was glued to the reflection. Note I only did reflectix on the top part (tops of windows upward.)
      5. Yes, same Reflectix everywhere. The flooring is reflectix holding up mineral wool batts and the walls are reflectix on the top with mineral wool.

      Good luck on your project!

  2. Aaron r

    This is really awesome! Thanks for posting. How did you get the subfloor back into the c channel? How did you get bolts through c channel into subfloor?

    1. Douglas Camin Post author

      Aaron –


      In my method I did not drop the belly pan or remove the shell, so I had to carefully plan how to install new bolts with each successive piece so I could access both sides of the bolt to fit on the nuts.

      I installed the boards landing in the same places as the originals but cut them into two halves to ease installation into the channel with the shell still on – you can see those cut lines in the pictures. Some folks have flexed the sides to put in whole boards, but I did not try that method. You have to be careful not to cut all old the bolts off or your shell will flex outward and it becomes much more complex to pull it back in. Fitting the board into the channel was a trial and error session with the saw. You’ll need to get a block to hammer against the board end to squeeze it in and sometimes use a pry bar or other tool to open the channel a bit as it will be bent and squeezed slightly. A scrap piece to fit into the channel and check the gap is useful.

      In my method I would cut the elevator bolts for the board I was about to install and then once that board was set, install fresh elevator bolts. Using this method the bolts would be installed at the ends of each board segment. In the front curve the bolts were good and I left them and in the back I had to replace the very back section of belly pan so I had easy access to the underside.

      In the end I replaced 90% of the existing bolts and managed to leave in and reuse the remaining 10%.

      Hope that helps!


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