I am converting a school bus into a home.  I have four questions I need assistance with.  The two things I’m trying to achieve is reduce thermal bridging between the exterior metal skin and the interior building materials, which will reduce condensation buildup.

It will be impossible to stop all thermal bridging, as the windows are aluminum framed and single pane.  Yet, I will have a wood stove and this should help with humidity levels.

I also am planning on staying in mild climates, because I don’t like the heat, and to avoid battling the condensation issue in cold climates as much as possible.

1a) I have insulated the floor with 7/8″ rigid insulation with 3/4″ plywood subfloor.  The floor insulation is to be taped at all seams, yet, I’m not sure of the best tape for that use.  I was thinking aluminium tape?

1b) While the floor could not have an airspace between the metal floor and insulation, should I put some type of reflective barrier between the insulation panels and the subflooring?

2) On the majority of my walls and ceiling, I will attach thin battens with offset air channels against the inside of the exterior metal.  Then, I will adhere rigid insulation to the battens.  The insulation will have a reflective side facing towards the interior of the bus.  I will then cover the insulation with something like a lexan flexible panel material.  A) Does this sound correct?  B) Should I also have an air gap between the reflective side and the interior panel covering? 

3) There are a few areas I cannot insulate as I described in #2.  These areas are not visible or accessible to me, so I’m trying to think of how to best insulate them. 

My first thought was spray foam (one step), yet my understanding is that it can be acidic to the metal, breaks down over time and can retain water.  Also, it needs to cure, and so I’d have to put a small amount in, let it cure.  Add another layer, and so on. 

I then thought of a two step foam, but the amount of areas are very small (20″ x 12″ x 1″), and the product is very expensive.

I can’t stuff anything in, so I’m almost wondering if I should simply leave the air space between the outside skin and the inside, then insulate the inside portion of the inside skin.  Laughing at me trying to clearly write this and you visualizing it.  Again, it’s not a large amount of space, but it happens to in the bedroom part of the bus, and one area is the wall next to my bed .

4) The bus walls and ceilings are lined with metal “U” shaped ribs.  I plan on applying some type of wood strips (either to the sides of the ribs, or like battens on the interior side of the ribs.  Yet, the latter takes headroom away) to attach the ceiling panels too.  Either way, this would create an air space between the metal ribs, and allow me to screw the ceiling panels into wood, not metal.  Should I cover the inside facing part of the ribs with a thin reflective material?  

Summary: I’m happy to say that I’m going as green as I can by using used or excess construction material I found on craigslist to be as green as I can in converting my bus.   Your help in making my “home” as mold and moisture free and warm/cool is greatly appreciated.

If you want pictures, please let me know and I’ll send them.

Steve Foreaker
[email protected]