Collins bus ceiling insulation questions

[farok]

I have a 6-window Collins which I'm converting to a weekend camper. I've ripped out the ceiling, insulation, and fixed the leaks. I'm planning on XPS foam board in roof. I'm 6'2" without shoes and the roof ribs are about 6'3" off my new floor right now, so headroom is at a premium. For the ceiling, I plan to install 1/4" plywood, so nothing fancy. The ribs in the bus walls and ceiling are 1 1/4" deep, but foam board comes in 1" and 1 1/2". Would it be best to just put 1" in the ceiling and screw the plywood to the ribs? I know I'm not eliminating thermal bridging this way, but for my use and desire to not lose headroom, I think this is fine, especially given the original bus windows and door are staying for now.

Any thoughts on how I could improve the ceiling insulation/bridging situation, without losing much headroom? Would 1 1/2" foam board be any more helpful? Is it worth the hassle given the rib height of 1 1/4"? Any alternative ways to attach the ceiling panels to avoid the bridging, especially if I were to go with 1 1/2" insulation?

Thanks!
Chris

[o1marc]

Where are you finding rigid insulation in 1-1/2"?

[farok]

The Home Depot in town sells it in 1/2", 1", 1 1/2", and 2" (or at least their web site says they do). Lowes only sells 1" and 2".

Maybe I should make sure the local Home Depot actually stocks what their web site says they should... haha

[o1marc]

Originally Posted by farok

The Home Depot in town sells it in 1/2", 1", 1 1/2", and 2" (or at least their web site says they do). Lowes only sells 1" and 2".

Maybe I should make sure the local Home Depot actually stocks what their web site says they should... haha

I think you are mistaken. Formular Rigid Pink comes in 4 thickness', starting at 1/4" and doubling in size up to 2" (1/4", 1/2", 1", 2"). I would have used 1-1/2" instead of layering 1" and 1/2" to get to 1-1/2". It's not on their website.

[ak91th]

1 1/2 Foam board



https://www.homedepot.com/p/R-Tech-1...0817/202532855

[ak91th]

Formular 1 1/2" pink


https://www.homedepot.com/p/Owens-Co...88WD/202085958

[o1marc]

Originally Posted by ak91th

1 1/2 Foam board



https://www.homedepot.com/p/R-Tech-1...0817/202532855

Be nice if they actually had some somewhere.

[farok]

I'll have to check my local store, but back to the original question, any concerns with just putting 1" foam into my 1 1/4" cavity, and screwing the ceiling panels to the roof ribs? Better ways to do it? Thanks.

Chris

[EastCoastCB]

Originally Posted by farok

I'll have to check my local store, but back to the original question, any concerns with just putting 1" foam into my 1 1/4" cavity, and screwing the ceiling panels to the roof ribs? Better ways to do it? Thanks.

Chris

Seems like a good compromise to me, man. Better than nothing and you won't be losing any headroom.

[farok]

Thanks for the insight!

[o1marc]

You can actually get 1-1/2" inbetween the ribs, fill that space if it's in the budget.
Where are you located?

[farok]

While I'd like to, unless the 1 1/2" foam is actually 1 1/4", then I'll probably stick with the 1". I may get out to Home Depot later this evening or tomorrow to double-check... I'm ready to get some and start filling. That and reseal the windows, and then I think I'll be nearly ready to start building again!

Chris

[o1marc]

You'll be happy with 1", no need for more.

[farok]

Thanks. I forgot to answer your other question. I'm in New Jersey, but don't plan to be in the bus when it's frigid outside. I'm expecting between the roof paint and the insulation that we'll be OK in the summer. We'll have a MaxxAir fan as well to help keep the inside cool if it collects too much heat.

Chris