Bus renovation damp prob.

On behalf of neighbour.His ceiling panels are buckling while renovating.Origional melamie type panels .About 3 mil thick.The insulation [batts] in ceiling feels damp on touch. The cavity is about 50 mil.In my opinion he needs to get air circulating through the roof by using vents.Is there another option.

whats stopping the condensation from dripping into the batts ?

He has water leaking in. Water will creep through the smallest cracks, if you can see it or find it water will get in. Until every leak is sorted nothing else will be a cure.

This inner ceiling is in its origional coach built condition.Now that they have just shifted up into the wet zone up in the hills,
this problem has emerged.Its not leaks as exterior looks really good.So its got to be condensation.Nothing stopping it dripping. Its happening right through the bus.I can see now that to fix this potential continious problem he will have to remove inner lining,remove the insulation and replace it with sheet polystyrene stuck to the ceiling.Maybe even prepaint/seal the panels before putting them back on as well.

the other thing is melamine panels will hold the moisture in. need a material that breathes so the condensation will dry out or put some drainage in. polystyrene won't hold water and it can drain down to the walls.
somewhere you need the water to drain out or evaporate out.

Just been ova for a look and chat.Problem is worsening by the day.Plan now is to remove all the ceiling panels.Remove the old batts etc,Cut and glue in poly directly to ceiling.50mil deep cavities.And your right.Water that does accumulate needs access out so provision for this is required.Prepainting all the ply panels will be done as well.I can see myself helping out quite a bit here.Ive done 2 housebus,s in my time.Never had this problem in them.

*3 is correct. Start on the outside first, reseal any vents and roof seams. you will seldom, IF EVER, SEE where water is getting in and if this problem is getting worse by the day, he has a leak!
You may see inside if it is an old leak but this sounds as if it is just starting.
Was the bus in one position for a period of time before moving next to you. If so more than likely settled seams have opened up a little to start letting water in.
I have countless vans that sit on site for say two to three years, as dry as a bone, when I pick them up and move them 99.9999% will develop leaks irrespective of age of van. You can crawl over them with a magnifying glass but seldom actually see where the ingress is. Once inside it will track in the weirdest ways and even capilliary uphill sometimes. The only solution is to reseal everything.
To get condensation that is enough to buckle the ceiling you would have to have, a totally sealed bus, about five people huffing and puffing 24/7 and a couple of unflued gas heaters going all day.