Flat-Tire
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Post by Flat-Tire on Dec 29, 2013 17:07:12 GMT -8
On my Cree (now renamed Da-Vid), the moisture barrier was originally installed directly after the 1/8 birch ceiling, then the insulation, then the tin. I have noticed that most install the insulation first then the barrier, then tin. Which method should I use? Is the barrier next to the tin or the birch?
I also noticed while watching mobiltech's videos, that the ceiling support ribs (ripped from 2 X 4s) are tapered at the ends where they meet the sides. Mine were 3/4" X 3" and not tapered. Is the taper to push out the tin? Should I follow that method or stick to the original design?
Thanks
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mobiltec
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Post by mobiltec on Dec 29, 2013 18:21:52 GMT -8
Hi Flat Tire...
The Forester I did in CO was the one with the one inch thick ribs. Those were tapered at the ends to keep the heads of the nails from rubbing through the metal skin.
Follow what is already there on your framing. I use 1x3s in the Shasta I just finished. You can go look at the 57 Shasta videos for your framing and vapor/moisture/condensation barrier.
There has been some discussion on the differences between vapor, moisture and condensation barriers and where they need to be. As seen, I put mine next to the metal on top of the insulation but you may wish to talk to others about this. What I am trying to prevent is condensation forming on the under side of the skin from getting to the insulation...
Welcome to the board...
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61 Shasta
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Post by 61 Shasta on Dec 30, 2013 19:37:16 GMT -8
Flat-Tire, when I did my Shasta I did a bunch of reading on this issue. However, I am now no smarter on the issue than I was at the beginning. Generally they talk about vapor barrier and air barrier. The short version is the vapor barrier goes on the inside and the air barrier goes on the outside. However, you need to be sure and not create an area where moisture can collect between. So, I kicked the can and used rigid foam with the vapor barrier on the side next to the trailer. I can tell you though, as Mobiltec says, there are more questions out there than there are answers. Even the experts can't really agree on the issue. As an example I offer this from one source: An interior vapor retarder is useful in heating-dominated climates while an exterior vapor retarder is useful in cooling-dominated climates. In most climates it is often better to have a vapor-open building assembly, meaning that walls and roofs should be designed to dry:[6] either to the inside, the outside, or both, so the ventilation of water vapor should be taken into consideration. A vapor barrier on the warm side of the envelope must be combined with a venting path on the cold side of the insulation. This is because no vapor barrier is perfect, and because water may get into the structure, typically from rain. In general, the better the vapor barrier and the drier the conditions, the less venting is required.Now if that don't get your motor started I don't know what will. I have come to the conclusion, albeit, too late for my unit, that simply installing fiberglass insulation in the voids with the vapor barrier side to the inside would be as effective on these units as any you can provide. My opinion. So, here is a picture of what I did to mine. If you want more info simpy google vapor or moisture or air barriers. I augmented that search with metal buildings to get that view.
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mobiltec
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Post by mobiltec on Dec 30, 2013 21:12:23 GMT -8
I love those photos Bill...
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Nomad95336
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Post by Nomad95336 on Dec 31, 2013 4:27:34 GMT -8
As an example I offer this from one source: An interior vapor retarder is useful in heating-dominated climates while an exterior vapor retarder is useful in cooling-dominated climates. In most climates it is often better to have a vapor-open building assembly, meaning that walls and roofs should be designed to dry:[6] either to the inside, the outside, or both, so the ventilation of water vapor should be taken into consideration. A vapor barrier on the warm side of the envelope must be combined with a venting path on the cold side of the insulation. This is because no vapor barrier is perfect, and because water may get into the structure, typically from rain. In general, the better the vapor barrier and the drier the conditions, the less venting is required. I take that to read as "condensation will occur when warm air contacts a cold surface", ie: the outside of your soda can on a warm day. Gotta Keep 'em Separated www.youtube.com/watch?v=XN32lLUOBzQ
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Post by bigbill on Dec 31, 2013 5:46:04 GMT -8
Owens-Corning research says to install the vapor barrier on the winter heated side. The reason is in cold weather the moisture will pass through the walls and condense in the insulation rendering it useless. Normally in warm weather the moisture in insulation has little or no effect on the insulation. Any time you add a vapor barrier you are trying to stop the flow of moisture. Over the years insulation has been made with vapor barriers one side, both sides, and believe it or not in the center. The general thought today is on the winter heated side. This is for the best insulation performance, but vapor barriers have been installed for other reasons than protecting the insulation. So with that said you have to decide what you wish to accomplish with your vapor barrier then install to please yourself. The ideal Vapor barrier would be located on the outside of both surfaces with no cracks that would allow moisture to enter walls, this isn't possible at a reasonable expense so we have to do the next best thing. The ventilation practices stated above are right but in a wall cavity they are not obtainable so that is why vapor barriers are installed. By now I probably have everyone totally confused, so I will close by saying good luck.
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Post by bigbill on Dec 31, 2013 6:02:22 GMT -8
One more thought. On these trailers the sealing methods we use along with the alum. skin we probably have created one of the best vapor barriers on the outside that you can have. When you compare our trailers to a residential construction our trailers are very well sealed. With that said I add an inside vapor barrier and say the heck with it. With all the design problems these units have a vapor barrier is the least of my concerns.
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mobiltec
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Post by mobiltec on Dec 31, 2013 7:48:39 GMT -8
I like the "Puff Factor" that I get from using flooring underlayment as a condensation barrier over the fiberglass insulation. It doesn't have anything to do with insulation other than the fact that it may increase the R factor a bit. But it sure gives a nice "Puff Factor"...
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Post by bigbill on Dec 31, 2013 9:56:22 GMT -8
Yes your trailers are beautiful when you get them completed, both inside and out.
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mobiltec
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Post by mobiltec on Dec 31, 2013 16:35:43 GMT -8
Well thanks Bill. That's a great compliment coming from you. Happy New Year!
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Post by bigbill on Dec 31, 2013 16:44:32 GMT -8
A compliment well deserved. Happy New Year to you also.
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