| Author |
Message |
Jim Stewart (H3jim)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 11:42 am: | |
As I'm finally starting to put up some sheathing, it occurs to me that perhaps a vappor barrier might be helpful. Its been hot here, with really cool nights. This am, there was even a puddle of dew on my tailgate. The bus ceiling ribs are all moist.
What have others done? After I get the ceiling covering over the plywood, is it pretty much a non issue?
I'm using marine grade plywood, I have 2" of foam on the ceiling, and I am putting the plywood directly over the stainless ribs.
Thanks |
gusc
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 2:15 pm: | |
Jim,
In a house the vapor barrier goes just under the wallboard to keep moisture inside the house from condensing in the fiberglass mat insulation. Water in mats tends to stay there a very long time. I don't think buses use fiberglas mats anymore but not sure.
The theory is that outside air will keep the insulaton dry if there is no constant condensation from inside but don't know if this theory works with buses.
Metal house windows are famous for condensation dripping onto the window sills and since a bus is metal I'm interested in seeing the responses you get to this.
If you use sprayed or solid insulation it may be a non-issue, I hope so because I don't even know what insulation my 4104 has! |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 22, 2005 - 9:47 pm: | |
If u have sprayed or real tight fit bloc, it's probably not necessary. However, as an added measure, add a blanket of plastic sheathing over the foam and framing that will be just under the ply sheating. Cheap, thin mil stuff from HD will do just fine. This also helps to prevent secondary air from seaping thru the ply at seams and leaving dirt streaks in carpeted headliners.
It only needs hung up good enough to keep it in place until the sheating is put on. |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 26, 2005 - 12:36 pm: | |
Hello
Vapour barrier is a tricky thing inside a bus.
The humidity and temperature variables inside a parked bus swing wildly up and down, far more than inside our homes. Leave your bus manuals on the table in the bus for a few weeks and the open pages will be wrinkled.
Also, one must be concerned with the sources of moisture, and how that moisture will be able to leave the insulation, once it gets wet.
Because wet insulation isn't a good insulator anymore.
Leaking through seams, or the cool skins sweating on the inside? Many of us have found soaking wet stock insulation contributing to the rotting behind the panels.
GM put cut-to-size fibreglass insulation into plastic bags, and then into the various cavities, ensuring that the insulation would not get wet from either inside or outside.
Closed cell spray foam is certainly a popular choice, as it doesn't soak up anything from either direction.
happy coaching!
buswarrior |
niles steckbauer (Niles500)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 26, 2005 - 1:01 pm: | |
This product has been used in construction for years - although it only protects against 'bulk' moisture and air transmission - the benefit is that it allows for moisture to 'escape' from the walls, which should help protect against trapped moisture in your insulation and the resulting corrosion problems - Niles
http://construction.tyvek.com/en/scienceConst/index.shtml |
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