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Old 02-17-2020, 05:34 PM   #1
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Insulation, XPS

Has anyone ever put XPS over the pre-existing métal in the walls and let it sit right on top of the ridge the seats usually rest on? Seems like that would be the easiest and create the best r value even you’re losing 2 inches of width?
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Old 02-17-2020, 06:20 PM   #2
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Has anyone ever put XPS over the pre-existing métal in the walls and let it sit right on top of the ridge the seats usually rest on? Seems like that would be the easiest and create the best r value even you’re losing 2 inches of width?
The insulation behind those metal walls was pretty worthless in my bus. I'm glad I took them out. Just now filling those cavities with XPS and wondering about adding more to be flush with that rail or not.
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Old 02-17-2020, 07:34 PM   #3
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I'm leaving the cavities between ribs in my walls empty and putting 2" XPS all the way from the floor to the bottom of the windows. This will cost me some width, but I'm doing a center-aisle layout so it won't be a big deal. The lip only sticks out about 1.5", so I'm going to either cut a notch in the XPS to fit over it or cut that lip off first (after calling International and finding out if it's structurally sound to do that - something I've been putting off doing forever).

I agree that this is both easiest and best for R-value. However, you still probably want to remove your wall panels and remove the fiberglass insulation. The inside of your walls is where all your leaking windows will be revealed to you.
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Old 02-17-2020, 10:00 PM   #4
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I'm leaving the cavities between ribs in my walls empty and putting 2" XPS all the way from the floor to the bottom of the windows. This will cost me some width, but I'm doing a center-aisle layout so it won't be a big deal. The lip only sticks out about 1.5", so I'm going to either cut a notch in the XPS to fit over it or cut that lip off first (after calling International and finding out if it's structurally sound to do that - something I've been putting off doing forever).

I agree that this is both easiest and best for R-value. However, you still probably want to remove your wall panels and remove the fiberglass insulation. The inside of your walls is where all your leaking windows will be revealed to you.
What's the purpose of leaving that gap in there? I I'm just about done filling mine in with 1 1/2 inch XPS. My lip is only 1 inch thick and I plan on doing the same, running 1" XPS above that rail to the bottom of the window. Below the rail I plan on running my Romex in some sort of chase, and probably fill around it.
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Old 02-17-2020, 11:05 PM   #5
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What's the purpose of leaving that gap in there?
I just don't want to go to the trouble (and expense) of filling it in, since I'll already have 2" of insulation in my walls.
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Old 02-18-2020, 07:01 AM   #6
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I just don't want to go to the trouble (and expense) of filling it in, since I'll already have 2" of insulation in my walls.
Gotcha. Lol ten character minimum.
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Old 02-18-2020, 09:45 AM   #7
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Has anyone just used regular home insulation and compressed it in to fit?
Saw a couple do that on you tube.
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Old 02-18-2020, 09:53 AM   #8
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Originally Posted by BusZen2003 View Post
Has anyone just used regular home insulation and compressed it in to fit?
Saw a couple do that on you tube.
Once you compress insulation you negate most of the insulating effect.

Youtube is full of fails.
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Old 02-18-2020, 02:02 PM   #9
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I would not use fiberglass batts. More tendency to absorb moisture. I put 1.5 between wall and ceiling ribs. And on metal floor. Have been very pleased.
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Old 03-15-2020, 03:55 PM   #10
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Hello, I'm about to insulate my walls with xps.
A question to the strengthening in the walls, can i remove them? Or will the bus be unstable without them?
It will be much easier without them to get the insulation in there.

Greetings
Mirko
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Old 03-15-2020, 06:58 PM   #11
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Hello, I'm about to insulate my walls with xps.
A question to the strengthening in the walls, can i remove them? Or will the bus be unstable without them?
It will be much easier without them to get the insulation in there.

Greetings
Mirko
Your bus won't collapse or deform without them, but they likely provide resistance to deformation in case of an accident by spreading the energy of a collision over a wider area (this is also something provided by the rub rails on the sides of buses). If you're not going to have people riding in the back near these, it's not a big deal to remove them - and even if you do, you'd still be stronger and safer than any RV.

That being said, I think it would still be pretty easy to put XPS in with these things still there. If you cut the piece and press it in partway, the edges of those things will leave indentations in the XPS and then you can cut partial grooves with a saw. The pieces should push right in then.
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Old 03-16-2020, 03:28 AM   #12
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If you use the method described above and make the cuts slightly narrower than the grooves, they will hold the XPS in place as a bonus.
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Old 03-16-2020, 07:49 AM   #13
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If you use the method described above and make the cuts slightly narrower than the grooves, they will hold the XPS in place as a bonus.
Yeah, just a mat knife cut would be better than a saw cut, good idea.
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