[malconium]

I was finally able to spend several hours today finishing the installation of reflective foil insulation in the walls of my 1973 31' unit. I am now ready to start re-installing the rest of the skins. Actually I have already re-installed the skins and end caps at both ends of the trailer. At any rate I thought that it would be a good time to pass on some observations that I have made along the way and to offer some suggestions to other who want to install reflective foil.

The main target of the installation was to fill each part of the wall cavity with reflective foil insulation in such a way as to keep an air gap on each side of the foil as much as possible. Foil insulation works more effectively if there can be an air gap on each side. So I bought some sheets of 1/2" and 1" thick styrofoam insulation board that I cut into 1" wide strips on my table saw. I had wanted 3/4" thick panels but for some reason that thickness was not availabe at Lowes or Home Depot at the time. Of course not it is.

I glued strips of the foam around the edges of each cavity and sometimes in the middle of larger cavities or ones that were especially curved. Initially I was installing the 1" strips first, glueing the foil to the 1" strips and then adding 1/2" strips on top of the foil in the same places where I put the 1" strips. Since the foil does have some thickness this means that the foam will have to compress a bit when I put my skins back in. This was not a problem when I installed the skins at the ends of my unit.

Somewhere along the line in one of the discussions that we have had here on the forums about foil insulation someone (I am sorry but I don't remember who) suggested that they were going to just glue the foam to the outer skin and glue the foil to it. There idea was to make sure and use glue that stuck well enough that the inner strips were not needed. I have since decided that this approach makes a lot of sense. So that is the approach that I have taken for about the last 40% of my installation.

So here is what I suggest as a good approach based on the experimenting that I did during my own installation:

1.) Use 1/2" or 3/4" foam cut into strips about 1" wide. Lowes has started carrying the foam board in 2' x 4' pieces which are much easier to handle than the 4' x 8' pieces I started with. The funny thing is that 4 - 2' x 4' sheets of 1/2" foam was actually a little cheaper than a 4' x 8' sheet when I bought the last of my foam. You can also cut it as you need it and return any unused sheets if you over estimate.

2.) Pick glue that sticks well to metal. I started using Liquid Nails which did seem to work OK but when I needed more I found another product at Lowes that was about 1/2 the price and works at least as well. The produc name is "Nail Power". It says that it is recommended for gluing drywall to wood and metal studs. I think I paid less than $1.50 per tube for it. It is kind of smelly though so make sure you have good ventilation. Liquid nails is not as smelly but I think I paid over $3 per tube and it does not seem to work any better.

3.) Just put strips on the outside skin and glue the foil to it. At first I tired to put the foam strips as tight to the sides of each cavity as possible. That is a little hard since some of the framing bulges here and there. I finally concluded that it was better to go for nice flat areas even if they were an inch or so inboard of the cavity edges. The foam is there to holf the foil away from the outer and inner skins. As long as it does that all is OK.

4.) There are some really odd shaped pieces of foil that have to be cut to fit around things like windows and etc. At first I tried holding a piece of foil up against the wall and used a razor knife to cut around the window frame. Right neart the end of my installation I found a much better approach. It turns out that if you hold the foil in the place where you want it that you can press the foil down around the edges of the obstacle. The back side of the foil now has a very nice line pressed into it that you can easily follow with scissors.

5.) I also discovered (late) that I could cut larger pieces for more than one cavity and mark as above. I cut then slit the foil so that it would clear things like cross members in the cavities.

I hope some of these ideas help. I would be happy to answer any questions that anyone has. I could also add some photos if it is not obvious enough what I am talking about. Also feel free to chime in with good ideas that you have discovered doing the same thing.

Malcolm