Condensation on the van ceiling?

[One Awesome Inch]

So when I go into my van to work on it there are big droplets of water and lots of condensation on the bare metal ceiling of my van. The van is empty and I am not spending hardly any time in it, maybe two to four hrs a week max.

I am concerned that when I go to put insulation on my ceiling, the water / condensation still might form there. I intend to put heavy plastic sheeting on all metal (roof and walls) in my van before I put in the foamboard. I will also put another layer of heavy plastic sheeting on top of the foamboard before I put on the final wood panelling.

Once I put all that plastic sheeting and insulation in, is the condensation and water droplets still going to form on the metal underneath the plastic sheeting?

 

[gypsychic]

My (very limited) understanding of dew points is that unless the temperature is above the dew point then yes the water droplets are still going to form. We are in basically the same climate (PNW) and I have researched this a lot since it is a big concern for me also. It is the reason why I was of the opinion to NOT put the vapor barrier next to the van sheetmetal as that just traps the water next to the metal. Again, my understanding is only from reading about it here and other places, but that is why ventilation is so important as well. It seems to be a 2 prong approach-keep temperature inside van above dew point and use fans/ventilation to move moist air out of van.

A question I was going to pose as I got farther along was if the issue at hand is rust-the water droplets being around the metal, then why not paint the inside metal surfaces with rustoleum or something of the like before doing anything else? I've only seen 1 van mod do this and it was a thicker substance but accomplished the same thing. The mod was done to not only help rustproof the metal but also help with sound dampening.

Others with a much better understanding and some practical experience will most undoubtable chime in. It seems that moisture issues are always a problem for any small space living situation, but combining many days/weeks/months in a row of heavy air moisture climate with the cooler (but not freezing) temperatures of winter in the PNW presents a unique challenge for this climate. But maybe not. Luckily there are many vandwellers/tiny house enthusiasts in this climate. check out blogs and YT for these issues.

 

[akrvbob]

The simple answer is that insulation and a vapor barrier will solve the problem.With the insulation directly against the metal, no warm moist air can get to the metal to condense. So buy Polyiso with a vapor barrier on both sides and then cover the joints/gaps with metal tape. All the warm moist air will be prevented from ever reaching the metal. Some heat might get through, but none of the moisture will.

No moisture=no condensation

On the other hand, if any outside air can reach the metal, it will condense if it's the right tempratures.
Bob

Bob

 

[One Awesome Inch]

Thanks for the info guys.

---

Two questions:

1. I assume I can just wrap the polysio in the heavy plastic sheet? I ask because I already bought the plastic and my local HD doesn't have polysio with a vapor barrier on it.

2. Instead of 'metal tape' can Tuck tape be used to cover all the gaps, joints etc? I ask because the previous owner left a bunch of construction materials in the van I bought and I got like 8 rolls of the stuff.

 

[One Awesome Inch]

 

[nowhhs]

When I built my house many years ago, the building inspector got very annoyed with me for putting a vapor barrier on the outside of the insulation and made me tear it out. At least in houses, the vapor barrier has to be between the living space and the insulation, and can't be on both sides of the insulation. After a lot of thinking about it, it probably makes sense, you don't want moisture trapped in your insulation which could allow mold to take hold, so if any were to get in, the lack of a vapor barrier on the outside would allow it to escape (eventually). I would agree with coating the sheet metal with something like spray undercoating before installing the insulation though.

 

[gypsychic]

The simple answer is that insulation and a vapor barrier will solve the problem.With the insulation directly against the metal, no warm moist air can get to the metal to condense. So buy Polyiso with a vapor barrier on both sides and then cover the joints/gaps with metal tape. All the warm moist air will be prevented from ever reaching the metal. Some heat might get through, but none of the moisture will.

No moisture=no condensation

On the other hand, if any outside air can reach the metal, it will condense if it's the right tempratures.
Bob

Bob

My questions about this are:

1)I have seen several places (do not know where now) that said there is no way to completely seal a van from moisture. some methods work better than others but there will always be moisture/air that reaches through insulation/vapor barrier. This seems pretty reasonable assumption to me, at least from not yet doing a van build.

2)If placing polyiso directly against metal doesn't that negate radiant barrier by leaving no air space?

Can't remember if 1AI is going to put a radiant barrier in. I was planning on it because although it doesn't get very hot for very long in PNW if I ever want to travel out of the area the radiant barrier would be helpful. Also it would be helpful during that 1 month of 80-95 days and all that insulation to battle the cold holding the warmth in for longer than an uninsulated van would.

1AI-not sure about the tape you are looking at but I have been looking at tape and realizing that there are temperature ratings on the glue. I'd look at temp rating of this particular tape to see if it will hold up in cold-hot temp ranges you expect. Remember that inside the van may get to hotter than ambient temps if you forget to block windows one day or are parked in the sun. I've purchased electrical tape that can be used in the hot environment of the engine. I've also purchased high temperature duct tape in addition to foil tape. I'd rather pay a little more and not have to redo something than obtain/buy cheap (or not the right application) materials and have to redo. My time, effort and frustration are worth something too.

Thanks,

GypsyChic

 

[flying kurbmaster]

I am curious 1AO what do you heat your van with when you are working on it and what work have you last done on it to get that kind of moisture inside. do you have wood stored inside your van is there some other source of moisture stored inside. I have owned vans in the pnw and don't remember droplets forming unless I was boiling water or using a propane stove. if this were normal every single vehicle would have this issue and all cars and trucks would rust from the roof down and have mold issues, there has to be a source of moist air somewhere. I would think??:huh:
that red tuck tape is used on vapour barriers, as a vapour barrier on windows, on foam insulation between house and siding, not sure if it will stick to this plastic sheeting you have as sometimes that stuff has a layer or film of sorts, where did you get the idea of using plastic sheeting from and for what purpose?? isn't that stuff expensive?? what do you hope to accomplish with the two layers, what is the thinking/benefits behind this? just curious

 

[highdesertranger]

here's my experience. on my last truck I had a fiberglass cap. in cold weather when we had it closed up condensation was terrible. we would only sleep in it except on a few occasions when I had to cook inside because of weather. still the condensation was terrible. so I insulated it with closed cell foam, like the old backpack sleeping pads, it was called insolite. then I carpeted over that. what a difference. before above 32 degrees the condensation would build up until it started to rain inside the cap, by morning I would be soaked. after the carpet would be wet, but it would hold it and not rain. during the day it would dry out. not sure if this would work in humid climates. below 32 the condensation would freeze on the bare fiberglass at night. in the morning you had to get out before the thaw or watch out chunks of ice would fall on you. after the insulation and carpet you could hardly tell there was condensation. the carpet would be cold but the carpet would hold the moisture. again during the day it would dry out. on a side note the cap was noticeably warmer in winter and cooler in summer. the condensation is going to form on the first layer it comes in contact with. a fuzzy surface has a lot more surface area are to hold moister. not sure if all this really helps anyone, but it is my experience. highdesertranger

 

[One Awesome Inch]

My questions about this are:

1)I have seen several places (do not know where now) that said there is no way to completely seal a van from moisture. some methods work better than others but there will always be moisture/air that reaches through insulation/vapor barrier. This seems pretty reasonable assumption to me, at least from not yet doing a van build.

2)If placing polyiso directly against metal doesn't that negate radiant barrier by leaving no air space?

Can't remember if 1AI is going to put a radiant barrier in. I was planning on it because although it doesn't get very hot for very long in PNW if I ever want to travel out of the area the radiant barrier would be helpful. Also it would be helpful during that 1 month of 80-95 days and all that insulation to battle the cold holding the warmth in for longer than an uninsulated van would.

1AI-not sure about the tape you are looking at but I have been looking at tape and realizing that there are temperature ratings on the glue. I'd look at temp rating of this particular tape to see if it will hold up in cold-hot temp ranges you expect. Remember that inside the van may get to hotter than ambient temps if you forget to block windows one day or are parked in the sun. I've purchased electrical tape that can be used in the hot environment of the engine. I've also purchased high temperature duct tape in addition to foil tape. I'd rather pay a little more and not have to redo something than obtain/buy cheap (or not the right application) materials and have to redo. My time, effort and frustration are worth something too.

Thanks,

GypsyChic

I don't plan on putting reflectex in or any other thermal barrier as it does not get hot enough for long enough up in Vancouver to bother me. I have a career and family where I live so I will not be travelling outside my area.

I will spend the money on the foil/metal tape if it indeed does reduce the condensation / moisture more than the Tuct tape. I don't quite understand how the metal tape would be better though. If one could please illuminate me on that matter it would be appreciated.

---

I am curious 1AO what do you heat your van with when you are working on it and what work have you last done on it to get that kind of moisture inside. do you have wood stored inside your van is there some other source of moisture stored inside. I have owned vans in the pnw and don't remember droplets forming unless I was boiling water or using a propane stove. if this were normal every single vehicle would have this issue and all cars and trucks would rust from the roof down and have mold issues, there has to be a source of moist air somewhere. I would think??:huh:
that red tuck tape is used on vapour barriers, as a vapour barrier on windows, on foam insulation between house and siding, not sure if it will stick to this plastic sheeting you have as sometimes that stuff has a layer or film of sorts, where did you get the idea of using plastic sheeting from and for what purpose?? isn't that stuff expensive?? what do you hope to accomplish with the two layers, what is the thinking/benefits behind this? just curious

Currently there is no heater or any kind of source of heat in the van whatsover. Its just an empty van with no human activity other than being in it a few hours a week. I do agree that it seems strange that there is so much condensation forming on the roof. Its almost always above 80% humidity here... usually 85 or so. Maybe, as Bob was indicating, the air is just so moist that when it hits the colder metal roof it condensates. So the question is if that happens to a metal roof in a van why does it not happen in a regular car? I think its because the roof of a car is covered in a "felt" material, not cold metal. The question is what about between the felt material and the metal roof? I think its because the moist air does not reach the cold metal therefore condensation does not occur. Pretty much what Bob stated.

To answer your questions...
The purpose of the roll of plastic sheeting is to prevent moisture from reaching the metal of the van's roof and walls. It was $30cdn for a 60ft roll and much cheaper than reflectix

My thinking is to cover every square inch with plastic sheeting to block the moisture from reaching the cold metal of the van.

The second layer of plastic sheeting would aim to prevent the moisture from reaching inside the walls' insulation... like a sandwich. Metal wall >plastic>2 inches of foamboard> plastic> wood panelling.

My main concern/question is if condensation will form between the first layer of plastic and the van's metal shell.

In fact what I am going to do is a little experiment with a piece of metal wrapped in the same plastic, and make sure its all sealed up and then leave it in the van taped to the roof and see if condensation forms inside... between the metal and inner side of the plastic.

 

[One Awesome Inch]

Here is a pic of the condensation I am talking about. Keep in mind this pic is taken shortly after I got into the van.

What I have done here is to dry (as best I could without a towel) a section of the roof and tape up a small piece of plastic sheeting. I placed a piece of newspaper under it as I figured it might be easier to tell if moisture is forming on the metal roof and still getting under the plastic as the newpaper would be wet... and quite obvious.

This last pic was taken after a couple hours of me working in the van. You can see the finger marks I left as I wiped the plastic. There was lots of condensation on the outside of the plastic, but the newspaper on the inside still appears to be dry and I cannot see condensation under the plastic.

This whole thing may be a no brainer but I really needed to be sure I am not going to get condensation (and therefore water, mold/rust) under my vapor barrier.

 

[gypsychic]

I love experiments. I plan on doing a few of my own. Sounds like yours had the same results HDR mentioned was his experience a few posts ago in this thread. The moisture condenses on the inner-most material. Still not quite sure why it's happening in your van in your area but not your car if no heat & no sleeping in van yet. Seems weird. Maybe it does actually happen in cars but it goes unnoticed because the moisture is within the fabric thread and dries out during the day, like HDR said. I'll have to start paying closer attention to moisture in cars in my area.

 

[LeeRevell]

This is why vehicles have headliners. I saw this same thing occur when I removed the headliner from two of my old cars. Put some kind of decent headliner up, problem solved. Insulation is simply a bonus.