condensation

[druidwood]

Ugh, just found at about roof condensation and have just read every article on this site. So while I understand about wanting to have a thermal barrier, the reality of trying to remove the roof panels which are all riveted is just too daunting (the lower walls were hard enough). My metal ceiling is not solid, but full of tiny holes, which I thought decorative until I painted - but they go right through. I am using electric heat and will be putting in a small wood stove for heat. It is VERY moist in the valley where I live. I do not mind the window condensation (original, single pane), but dripping on my head and belongings is no good. The floor has 3" of rock insulation and the lower walls have 1.5" so did all that part right in terms of having insulation and a thermal break.

SO does anyone have experience dealing with leaving the metal ceiling in place? How I can seal my porous ceiling so that the moisture on the inside of the outer skin cannot leak through? Using perhaps a paint on sealer for the ribs in particular? Attaching some sort of thin, and non-metal ceiling material over the current ceiling? Cut out sections of roof to replace insulation? Ideas? Thanks.

 

[Robin97396]

Those thousands of tiny holes are perforated ceiling panels. Yes you could cover those so water doesn't drip on you, but then you've got to ask where the water is going and what kind of problems can it cause, including health issues. As long as moist air can contact the outer skin of the bus, from the inside, you're going to have condensation issues. There needs to be some kind of filler that keeps moist air away from contacting the interior skin surfaces. That's why so many of us use spray foam after removing the interior ceiling panels. Rigid styrofoam insulation panels cut to fit tightly against the interior of the roof are about the second choice. Others use combinations of various kinds of insulation.

So to answer your question, most of us only put up with the dripping ceiling the first year before we're convinced we need to remove those ceiling panels and insulate.

 

[Jolly Roger bus 223]

You can leave the panel's up and spray foam inside the panel's in place because the foam does expand and with the many holes you have you can see exactly how much it expands and after a few practice shots then you will know exactly where to drill the hole for the next shot.
Then cover with a LUAN,birch ply or tongue and groove?
If you want to keep the metal ceiling look you could skim coat it with bondo?
None of it is a cheap option .

 

[EastCoastCB]

I can have your ceilings de-riveted and out in less than a day. Come on over!

Seriously, I'll do it. Just a wee bit of a drive.

I did a whole bluebird 30 footer's ceiling panels in two or three hours once. Its really not bad once you get the proper tools and get a rhythm going.

 

[druidwood]

I wish I could pay you to do it EastCoastCB, but yes Florida is a long drive. I would have to hire it out, as I have neither the right tools or the physical stamina anymore for such an endeavor, it is finding someone that really knows what they are doing that would be tricky. I also raised my floor 3" more than most people because I wanted the floor warm, so adding a new ceiling will bring my clearance down pretty low. I keep thinking the hard part is over, when a new problem appears. Not for the faint of heart doing a skoolie.

 

[Robin97396]

The problem with leaving the ceiling panels in is they will continue to conduct heat/cold to the interior of the bus. Naturally when it's cold I'd expect to see condensation at least where the ribs contact the metal interior ceiling panels.

It's certainly a personal choice dependent on where you live and what you want from your bus. Beyond the condensation issues of cold weather, I didn't want to be sweltering in this bus during the summer either. I already attempted AC before I insulated and was unable to cool this big metal box during the summer heat. As I've said, I'd make different choices if I was doing this again by using rigid insulation rather than spray foam.

It took me closer to a month to remove my interior ceiling panels.

 

[druidwood]

Thanks Robin. I will probably come to the conclusion I have to do this, just like with the floor, then the lower walls. I am going to have to live in the bus for several years so it should be comfortable. I have seen people use the rigid insulation, but how did you cover the ribs, which is where most of the water is coming from? I have a height issue so don't want the ceiling down much lower than the ribs. Also can I ask what did you use for ceiling material?

 

[Rusty-SKO]

Hang-in there Druid ! It is a long road, but dotting the T's and crossing the I's will pay-off in the end.

Some of you on this Board live in some cool areas ! I googled Sheet Metal near Gold Bar and found these: call them, tell them what you have, if they decline the job, ask for a direction/suggestion to go next. Maybe a trade school. Maybe a Prison work program.

Sound professional- they don't want to deal with no-shows or flakes.

I got a school bus here- I need the sheet metal ceiling inner skin pulled, about a 1000 rivets- is that something your guys can get done for me?


Good Luck !

 

[druidwood]

Thanks Rusty. I didn't even know what kind of business did this kind of work. I will make some calls to get idea of cost.

 

[family wagon]

ECCB isn't exaggerating, though he is experienced in the art of rivet removal. An air chisel maintained with a good edge will shear the rivets off in a jiffy. (I don't recall if that's his preferred method.. but anyway, it's at least one quick method.)

Here's the thing about condensation: it's what happens when the temperature on a surface drops below the dew point of the surrounding air. That's all there is to it. We're accustomed to seeing condensation on metal and glass surfaces, but it's not limited to those. To keep condensation at bay there's just one thing to do. Don't let surface temperature get below the dew point. There can be all kinds of devil in the details of how that's accomplished, but don't lose sight of this principle. You can prevent condensation by controlling surface temperatures and dew point (in other words, humidity or the amount of water vapor in the air).

Insulation alone isn't the whole answer. That slows heat transfer so we can have one side of a wall assembly warm while the other side is cold. Insulation doesn't necessarily prevent the flow of water vapor. If water vapor can permeate through the insulation then it'll do so. That leads to condensation happening somewhere within the wall assembly (the interior side of the outer cladding, or even somewhere within the insulation).

You could create a vapor barrier on the interior side of the perforated metal. That would significantly cut down the water vapor that gets inside the ceiling and condenses (though if the ceiling surface is cold enough, water will just condense on that vapor barrier surface). Despite your efforts some vapor will still get inside that assembly and condense, so give a little thought to how it'll drain or dry out.

Many of us are big fans of foam whether sprayed or placed as solid boards/sheets. I count myself among that group. It's convenient that closed cell foam can be both an insulator and a vapor barrier (when it's thick enough). It's not the only answer, though; there are a variety of ways to use insulators and vapor barriers to keep moisture in check.

 

[Robin97396]

It's usually about 2000+ rivets, depending on the bus. I was surprised that some people actually counted them.

Some people have done the entire job with a hammer and chisel. I used air tools and I'm still complaining.

 

[Rusty-SKO]

Thanks Rusty. I didn't even know what kind of business did this kind of work. I will make some calls to get idea of cost.

That's the thing- most of these places won't even want the work (don't be offended), but if you ask them, they will think of someone. Trick is, just get the ball rolling.

 

[druidwood]

Yeah Rusty, I checked google and local metal places are all manufacturers, so wouldn't want this type of work. So put an ad on craigslist for someone with a power chisel and experience. Worst case scenario I can see if I can borrow a power chisel and see if that works better than drill/saw that I used to do the lower wall rivets. Have to admit that the idea of selling the bus has occurs to me of late.

 

[Twigg-SKO]

There are two issues going on here ... Insulation and Thermal Break.

Insulation has been pretty well covered.

To create a thermal break you need to ensure that nothing metal has an unbroken run from inside the bus to the exterior. As the ribs are riveted to the outer skin AND the inner skin, they form a perfect conduction route for heat transfer. In the summer, any exposed screws will become radiators, and in the winter they will produce "inside rain" ... so you have to break the path to reduce the problem.

The easy way is to screw wooden blocks to the side of the ribs, and let them protrude a little below the ribs. Then fill in the ceiling insulation, then attach your final ceiling to the wooden blocks.

That provides an air-gap between your ceiling and the insulation above it (R3 per inch value), and means that metal fasteners never connect through metal to the roof. You can add a second vapor barrier too which will keep most moisture out of the roof-space.

This is not a perfect solution, but it's pretty damned good and will reduce your roof condensation to a minimum while helping you keep cool in the summer.

The really brave, with the really high head room, could consider removing the ceiling and adding foamboard, then replacing the ceiling. Then add an unbroken run of foamboard to the entire underside of the original ceiling before finally finishing with beadboard, or similar, glued on ... or simply bury the ribs under 4" of foamboard then screw to the rib framing blocks as above.

A critical component is not adding moisture to the inside of the bus ... so no open-flame propane heating and maintain good ventilation (Fantastic Fans are fantastic for this)

 

[druidwood]

Thanks Steve. The idea of a air space between insulation and roof sounds good - might give a chance for any condensation to dry - double barrier sounds good as well. If the block just sticks down 1/2 below rib then I won't lose too much headroom. Just need to figure out a ceiling that isn't wood - my metal one is pretty nasty so not really reusable.

 

[Robin97396]

Hey, you're another one of the 28' TCs with the 22.5 wheels.

You could always use that paneling that appears to be made from plastic. Why don't you like wood?

Many of us have discussed using the metal ceiling panels for covering windows on the exterior. The panels won't fit horizontally, but vertically they'd be able to cover two or three windows each.

 

[EastCoastCB]

I wish I could pay you to do it EastCoastCB, but yes Florida is a long drive. I would have to hire it out, as I have neither the right tools or the physical stamina anymore for such an endeavor, it is finding someone that really knows what they are doing that would be tricky. I also raised my floor 3" more than most people because I wanted the floor warm, so adding a new ceiling will bring my clearance down pretty low. I keep thinking the hard part is over, when a new problem appears. Not for the faint of heart doing a skoolie.

You really don't need to "know what youre doing".
Just a cheap air compressor and a fifteen dollar air hammer with a sharpened chisel bit and you'll be shearing them off with little effort.
You don't have to lose headroom. Throw some foam board up where the batting is now, and panel back over with luan or something. Still WAY better than steel and fiberglass.

 

[plfking]

The easy way is to screw wooden blocks to the side of the ribs, and let them protrude a little below the ribs. Then fill in the ceiling insulation, then attach your final ceiling to the wooden blocks.

That provides an air-gap between your ceiling and the insulation above it (R3 per inch value), and means that metal fasteners never connect through metal to the roof. You can add a second vapor barrier too which will keep most moisture out of the roof-space.

I was planning on doing just as you describe (wood blocks protruding 1/4" lower than ribs) and affixing 1/4" thick rubber tape to ribs......but then putting my non-perforated ceiling back in place (it's in fantastic shape and I really like the look of it). As long as I'm screwing into the wood and not the ribs, and the ceiling is touching nothing but wood, foam board, and rubber-covered ribs, I should be okay condensation-wise, correct?


Don

 

[Robin97396]

It sounds reasonable when you say it like that.

Others have attempted to put their panels back after insulation. I only remember one time when they didn't give up.

 

[druidwood]

Wood is just heavy Robin and that is a concern with my 5.9L engine. As this metal is perforated not good for window replacement, but might work for the bottom of my water tank frames - so good idea to keep it.