Originally Posted by indigocenter
Then what did you use????
For starters, what worked in our situation may not be suitable for you. I had previously researched everything with the idea of converting an Eagle coach. I had looked into spray foam. In our case, it was not practical and it was cost prohibitive. Time passed and the cost has dropped a bit, but other aspects of foam have not changed. The only spray foam in the bus is Great Foam.
Despite what some on this forum will say, there is is no single way of doing this.
Double walls have been used for a long time. The oldest house David worked on that had double wall construction was built in the early 1800's (the Talley House started out a log cabin and morphed into a colonial mansion over the years double walls allowed it to be insulated for modern living). David and I had to convert the bus while we were living in it. I'm still living in it and still working on it. We basically built a house inside a metal shell. We were capable of building a house inside of almost any shell. And we build using the same principles we used in building or remodeling any building. Foundation must be sound. Roof must be sound. Walls must be sound. Windows must be leak free. Then we would start upgrading and replacing.
For the Blue Bird, we kept the original walls and insulation. We simply added another layer to the existing walls. Double walls are used primarily to boost insulation. Exactly what we used ours for. 1X2 and 1X3 furring strips were shimmed out to 1". Then 1" thick rigid foam sheathing was added between the shimmed out furring strips. The foam sheathing we used happened to have a radiant barrier (facing the interior). Our first choice would have been either the pink (Owens-Corning brand) or blue (Dow brand) but it was not available in this town. The furring strips gave us a thermal break (we were careful to not screw wall coverings and cabinets thru the furring strips and into the sheet metal which would create a thermal bridge). It does make a huge difference.
Buses, even within the same brand, are not built the same. Our particular bus has 2" fiberglass insulation that from what we can tell it's all in good condition and is more like the insulation they put in residential ranges & ovens. Very dense and effective, except for the two million rivets. I think Blue Bird pays their riveters by the pound. It does not matter what kind of insulation you put in your bus, if you don't put thermal breaks in as well then you are just wasting your money.
Our floor is rubber on metal. No plywood was in our floor. We put roofing/subfloor grade OSB (made with exterior glue) on top of the rubber flooring (screwed down). I am not worried about the OSB "falling apart". A piece has been setting outside in the NM weather for well over a year. Other than being grey from the sun, it looks just like the new stuff. Trafficmaster Ceramica tile was glued (PL375) to the OSB. Under the floor, David stuff some fiberglass batt insulation as a temporary insulation. He was going to replace it with rigid foam sheathing after he built the waste tanks and added another fresh water tank. Now it's up to me. The fiberglass insulation will get removed this summer so I can travel in the bus. The insulation will not be replaced until closer to Dec. I know what was planned. I can do the work. Just takes me longer to do it. Only the center strip between the two beams will get insulation. The sides next to the walls get various boxes hung under them so insulation gets iffy. Some boxes, like the fresh tank box and the water bay will be insulated and heated.
If I decide I need more insulation in the ceiling, I will use George Myers method of Super Insulating the Roof
. I have conversed with George for many years via coach forums and private emails. I trust him on a great deal of things far more than I trust a great many on this forum. As an electrical engineer, he helped a lot the electrical side of a hydronic heat system I had designed for the Eagle (shelved the plans when we scrapped the Eagle). The coach forums folks helped me a lot. Much of which, adjusted and refined, has found it's way into the Blue Bird.
In NM, yearly temps range from single digits (have experienced lows of below 0F) to triple digits (110F). Insulation and thermal breaks help with the extreme temps.
You need to do your own research. Read what others have done but before you do anything someone else has done (or theorized about), you need to read up to see if it will really work for you (or if it is even doable without it falling apart). I have seen posters espouse methods that elicit response from laughter to horror. There is a reason I put the thread for the Noshockzone.org on this forum.