Headliner keep or remove?

[HamSkoolie]

The problem with injecting foam expanding foam into enclosed spaces is that IT WILL cause problems. Expansion will spread sheets causing ripples or buckles. Areas will not have sufficient room to expand and so will give far less insulation than the same thickness properly expanded....remember the expansion causes gas filled bubbles and it's those gaseous voids in the bubbles that insulate, not that material forming the bubbles. There may also be cure issues if insufficient expansion is allowed.
I've read the issues about the panels fitting back up. I'll be working largely alone myself. I will get help to lift a few panels up and secured with a couple of screws in the panels, likely the ones in the front to rear stringers, along with the ones in the ribs on the side that the factory used to hold the panels. Then it should be a simple matter of working from the inside to the outside without tightening anything until all screws are in a particular panel.

 

[musigenesis]

I thought about cutting a slot into each 'bay' that needed insulation, pulling the batting out throught that slot then spraying in foam. I think it would have worked but I also think it would have taken just as long that way and I probably couldn't have gotten all the batting. It would have been hit or miss. If you didn't remove the batting, all you'd do is end up with blobs of foam around each hole and not even distribution.

Whatever structural stiffening you're deriving from the headliner is gone as soon as you cut it like that (unless you weld it back up, which would burn away the foam underneath). Might as well just remove it at that point.

 

[LargeMarge-TC]

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[edited for brevity]
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...If you didn't remove the batting, all you'd do is end up with blobs of foam around each hole and not even distribution.

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re -- uneven distribution
Based on my experience, I am amazed at the enthusiasm of expanding spray-foam insulation.
It expands to fill, nothing stands a chance after it gets up a good head o' steam.
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re -- voids
I tap to locate unfilled areas.
A new hole drilled, a quick squirt, and that seems to be the ticket.
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re -- remove batting
I think removing insulation so I can add insulation is... counter-productive.
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On our rig, part of the insulation 'package' is our photovoltaic system above the roof.
(On a stand-still house, eaves can contribute to slowing the air-change against the exterior walls.)
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I think of the entire vehicle as a holistic environment.
I think parts of systems need to contribute to that complete system, just as all the systems flow symbiotically.
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A home-built rig can be simpler, because we do not need to park it on the revolving pedestal at the dealer, impressing tire-kickers with fancy decals, chandeliers, or frighteningly-complex electric systems.
Or holes in the roof [spit].

 

[HamSkoolie]

I'm with OldYeller on this one.
Not removing batting and trying to ad expanding foam is a bad idea.