Vapor Barrier

[Classic Finn]

I was wondering if there is a need for a vapor barrier of sort between the styro and ply on the ceiling?

Should the inner ply under the aluminum be varnished or clear coated?


Classic Finn

[Keith B]

If you insulated I don't think you'll need a "vapor barrier" so to speak, not like a house, plus, if you put a plastic vapor barrier up you lose your wood glueing surface inside. Your TD is not fully climate controled like a house, vapor barrier on a house is a good thing, but on a TD I don't believe it's necessary. On sealing the ply up prior to aluminum, I would vote for yes... The aluminum is not 100% sealed, you have trim pieces, it moves around, caulking can get old a crack, shrink over time, etc, so I think some moisture, be it actual water, humidity, condensation etc. will get between the aluminum/ply - if there's any air space (floating aluminum) without a vacuum there will be "moisture"...thus why windows are vacuum sealed...... Now if you contact cement your aluminum to your TD, you probably don't need it...but that's another question of preference... Anyway....anything and everything you can do to protect your wood at this time would be in your best interest... I know many favored methods include epoxy, CPES, polyurethane, primer and paint, etc...
In short, my vote is no vapor barrier.
Seal the wood.
Install the aluminum or whatever covering you decide on.

[Classic Finn]

I have a good sealant on all wood areas... I was just wondering if anything else was necessary.... carefully forward and making good progress... since the weather has been favorable in my Open Arctic Skies Shop...

Had to ask because it was bothering me for sometime... so back to work ..

And thanks for your reply once again...

Best regards
Classic Finn of the Far North.

[Keith B]

If you want a 2nd opinion ask MadJack or Doug Hodder or someone who's built MORE than one tear...they know the downfalls or what does and/or doesn't work I'm sure... personally, I have plywood interior (1/8") and exterior (3/8"), framing/insualation (1/2') in-between, no "vapor barrier" and I'm sealing the exterior w/ Epoxy mixtures and the final coat will be primer and topside marine paint... check back with me in 10 years to see if she's rotted out

[madjack]

Heikki, I think that Keith summed it up pretty well....................................

[Classic Finn]

If you want a 2nd opinion ask MadJack or Doug Hodder or someone who's built MORE than one tear...they know the downfalls or what does and/or doesn't work I'm sure... personally, I have plywood interior (1/8") and exterior (3/8"), framing/insualation (1/2') in-between, no "vapor barrier" and I'm sealing the exterior w/ Epoxy mixtures and the final coat will be primer and topside marine paint... check back with me in 10 years to see if she's rotted out

Keith think in 10 years I wont have this anymore.. I most likely will have Voyager 2 or 3...

But yes you summed it up very well....it will be water proofed so well that I,ll be able to take it out to sea...

Look in the Headlines of The Newspaper... Crazy Finndian sails the 1st tear drop to the Americas... HAH..

Classic Finn

[Classic Finn]

Heikki, I think that Keith summed it up pretty well....................................

Yupper ... That he did...

Classic Finn

[48Rob]

Heikki,

I agree that the ply the aluminum will be laid over should be sealed...unless you choose to glue it on.
If it's glued, the glue will be the sealer.

As for vapor barriers, it is important enough to spent $3.00 for some plastic.

While teardrops are not climate controlled like a house, and don't face the constant difference in temperature and moisture levels between the living space and the outside air that allow condensation to form inside like a house, it still occurs.

In a teardrop scenario, condensation forms, generally, whenever people are inside breathing, and the exterior surface of the tear is slightly cooler than the inside.

The warmer vapor (breath) of the occupants, and any moisture present in the trailer or its furnishings, condenses on the cooler areas of the tears walls, windows, and ceilings.
The average couple exhales a litre of moisture in an 8 hour period while sleeping, more when awake.

The vapor is not stopped simply by the fact that there is a sheet of paneling and some insulation between the occupant and the roof; it will migrate around and through.
When it arrives, it will condensate and worse case it will drip, or otherwise transfer to the insulation, and or wood, and soak in wherever possible.

Agreed, the amount of condensation/damage that can occur is generally minimal since most camp in warm weather, but it still happens even in the summer.

For those who camp in cooler weather, the amount of potential condensation related problems vastly increases.


Some of you may be scratching your heads thinking what is he talking about, Condensation is never a problem here in the dry Southwest...and you may be correct, but for those in more humid and cooler climates, the issue is more than just a passing concern...condensation does a lot of damage.

Too much condensation causes many other problems besides the little drips of water that we sometimes must wipe off the windows and walls when we wake up in our tears.
Once it has taken a hold (besides mildew and mold) the dampness will cause the paint/protection to loose it's grip on the wood you so carefully sealed, so any wayward moisture would not affect it.
But now that the sealer has failed, the moisture has soaked into the wood...

Ventilation is of course a wise practice.
Most leave a window or vent open to help avoid depleting the oxygen in a tear, but on a cool/cold night, it is a balancing act between proper ventilation, and staying warm.

Most open up, or ventilate the excess moisture from a tear in the morning, and a tear that has no insulation or cavities can be ventilated pretty quickly, but one that has insulation in a fairly well sealed cavity, cannot be properly ventilated in 5 minutes.
A vapor barrier however, will contain the moisture to the open living space, where it can be quickly dissipated.

The whole point here is that if one is building a trailer from scratch, the addition of a vapor barrier is a good thing, not something to be dismissed as an impractical bother...

My thoughts...


Rob

[Classic Finn]

Rob

The reason for asking this is .... as you know we are a culture of the Famous Saunas ... Granted I hope the tear will never get that hot nor even close..

A good Sauna does have a vapor barrier for moisure and mold prevention.. vents are installed for air wether cold or hot can escape and cause no damage to the wall paneling .... be it cedar, pine or any other. and in between the walls is a special plastic film or sheeting ...

Having built a few of these "Self Inflicted Torture Bins" I had the same in mind for the teardrop...However never built such nor even camped in one I didnt know... so I wanted to get the question out and get important opinions as I have received and for which Im very thankful..

Sounds maybe a bit ridiculous but .... here many of the builders had the same advice... as to add that extra few cents or dollars to install it..

Plus we have the windows on both doors in addition to the Finn Tastic Vent ... and if need be there are plenty of tiny extra fans available for a few dollars...

Thanks everyone for your replies.. I dont take these replies for granted.

Classic Finn

PS Maybe was thinking it will be a Sauna on Wheels...