Originally Posted by EricW
I will be getting my ceiling spray foamed and have tongue and groove ceiling to finish. I have double wall black pipe and need to figure out how to get through the ceiling. Is the triple wall insulated enough to just go straight through and insulate up to that? If I leave space or use one of the metal thimbles will I end up with condensation in the summer when running AC? I was thinking of trying to do some sort of thimble or air box around it where it goes through the roof and cut some insulation to cover it in the summer? I may be over thinking again
The only safe way to run a solid fuel chimney through a wall or roof penetration is going to be similar to what Nat described above. To meet pipe manufacturer's spec, though, you need to support the chimney structure at the roof or wall penetration with a part made by the chimney pipe manufacturer for that purpose. I'll post specifics separately.
People manage to burn their homes down due to inadequate clearances despite all the room they have for proper installations. In vehicles, we are dealing with much tighter spaces than in homes. Here are some general rules:
1) Use only double wall connector pipe between the stove and the roof jack. (Double wall connector requires only 6" clearance to combustibles, while single wall requires 12" to 18" depending on heat shielding.)
If you're using a modern EPA approved stove (and you should be, for the higher efficiency, cleaner burning, cleaner/safer chimneys and the reduced pollutants in the air right outside your door!) then it is often counterproductive to use a single wall pipe anyway. You need some heat in the exhaust just to maintain a good draft and a clean chimney. These certified stoves are efficient enough that you're not losing anything with double wall pipe.
2) Use Class A packed pipe for all roof or wall penetrations, and for any portion of the chimney that is outside the vehicle. Class A pipe requires 2" clearance to combustibles.
3) A metal wall/roof panel - or heat shield - is not considered non-combustible if there is a combustible material (like insulation) behind it. You still need to measure all the way TO the combustible material for proper clearance.
4) The old saw that "heat rises" only applies to convection. Radiant heat moves in every direction including sideways and straight down until it hits something. Be sure that what it hits either meets the non-combustibility test in #3 or, if not, that it is far enough away to be safe according to the stove manufacturer's tested clearances.
One of the better sources of installation information for skoolies is Marine stove manufacturers. They do beautiful and safe installations in tight spaces all the time. They make some nice stoves, too!