Interior condensation

darth_linux

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Hi all

I've got my '66 Newport parked (outdoors) for the winter. It has one of those grey car covers on it, can't remember the make. It's been pretty damp out lately, and it just started getting below freezing last week, and today we had our first actual snow.

Last night, while putting snow tires on my daughters car, I needed a tool out of the trunk of the S.S. Anderson, so I removed the car cover, opened the trunk lid, and discovered a LOT of frozen condensation on the underside of the trunk. Like, it was literally covered in frozen water droplets!

I've never seen frozen condensation on the underside of a trunk lid before in my life - what could be the cause? Is the car cover not letting moisture evaporate out of the interior of the car? If so, should I remove the car cover and just let it sit, covered in the snow for the winter?

Thanks in advance for your tips and suggestions.
 
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If the condensation is on the inside of the deck lid, no place for it to escape, so it stays there. Same for the hard rubber trunk mat, if it's still there. If the car has sat since the formerly warmer weather, that could be the cause. Perhaps, on non-snow days when the humidity is low, you could raise the deck lid and let things air out? Might check the floor carpet inside, too.

Most quality car covers will resist moisture intrusion, but also allow any moisture under them to evaporate out, typically. Otherwise, having the vehicle covered would cause other issues due to the retained moisture.

Just some thoughts,
CBODY67
 
Normally do you have any leaks in the car? If you are getting that much moisture in the trunk, I don't think removing the cover is going to fix that. We cover one of our cars during the winter months and it stays nice and dry inside. The cover was designed to let it breath. We have been doing it for years with excellent results. There are more than a few opinions on outdoor car covers. A lot of people do not like them. We have always bought quality ones and had good results.
 
I think interior compartment condensation is what kills most cars outside of arid areas like the desert south-west US and high plains.

The air that was trapped in your trunk when you last had it open might have been 50% humidity at 70 F but when the temp dropped the water vapor that was still in that air had to condense on the cold surface that was your trunk lid.

I posted this pic maybe a week ago in another thread. This is what I'm doing for the past year or two since I've had these cars outside (300m's):

car-cover.jpg


Wrapped under and over with 6-mil vapor barrier. Under that is an indoor-quality car cover (non-woven polyethelene fabric). My goal here is to keep rain / snow from touching the car, and to keep the ground-level humid air from attacking the undercarriage.

But here's another trick: Silica gel beads. Those little beads you see in packaging, pill bottles, etc. You can buy it in big 5 and 10 lb bags - there is a brand of cat litter that is actually silica gel beads. Lay some out on a piece of cardboard or make a cardboard tray, put it in the trunk, inside the car cabin, under the car if you wrap the car up like I did. The beads will soak up water vapor in the air, lowering the humidity. You can re-use the beads later by putting them in the oven at low heat - they'll give up the water and dry out and you can use them again.
 
my '66 Newport parked for the winter.
Where exactly? If stored outdoors even under a cover, there is your answer. One of my cars is parked in an unheated garage and I've had the same issue particularly in the spring and fall. If I notice a drastic change in temperature I try to remember to plug in a small fan and put it on the floor under the dash for a few hours right after the temperature change to keep the air moving. Consider cracking your hood and trunk lid open under the car cover to aid air circulation. Another issue for winter storage is mice. Although we have 2 cats, my insurance is dryer sheets tucked in various nooks and crannies where there is wiring.
 
The cars only been parked for a month. No water intrusion in the cabin at all. I’m just a little skeptical that the trunk would be so airtight that moisture couldn’t evaporate out … I might bust out the shop vac when it warms up next week and suck out the water. No rubber mat anymore, just a utility carpet cut to fit.
 
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Where exactly? If stored outdoors even under a cover, there is your answer. One of my cars is parked in an unheated garage and I've had the same issue particularly in the spring and fall. If I notice a drastic change in temperature I try to remember to plug in a small fan and put it on the floor under the dash for a few hours right after the temperature change to keep the air moving. Consider cracking your hood and trunk lid open under the car cover to aid air circulation. Another issue for winter storage is mice. Although we have 2 cats, my insurance is dryer sheets tucked in various nooks and crannies where there is wiring.
It’s parked outside but not under a car park, just the cloth car cover. Thanks for the tips!
 
There is quite a bit of water vapor that comes from the ground under your garage floor and straight through the concrete slab and into your garage. Rolling under your car a cheap remnant of linoleum flooring that you can buy from a carpet / flooring store can help keep that mosture UNDER the linoleum when it condenses into a liquid instead of it condensing on the underside of your car. Or you can lay out that vapor barrier on the floor, corner to corner and drive over it, let the water vapor condense under it and keep it from reaching your car.
 
Have a look at this chart: Dew Point Chart (Degrees) - Simple & Fast

It only goes down to 10 C (same as 50 F). So let's say it's a miserable few days, cloudy, rainy, 50F outside, humidity is really high, 80 to 100%. No, your car is not air tight. Your trunk is not air tight. Maybe it will take 3 days, but at some point the inside of your trunk will also be 50F and 80% humidity. On the chart, where 10C and 80% meet, it says 6.7. That's degrees C, which is 44 F. So outside it stops raining, but it gets cold. It drops to 40F. It might take an hour or so, but your trunk lid will also eventually be 40F. Once the inside surface of the lid reaches 44, the water vapor inside the trunk will start condensing on it. If the outside air temp goes below freezing (below 32) and stays there for a while, then eventually the water beads that are condensing on the inside of the trunk lid will freeze there.

The thing is, if outside temperature and humidity changes are gradual, very gradual and slow, then the air in the trunk will follow those changes (with a huge delay, maybe a few days) and you won't actually ever get condensation. Now think of other compartments in the car, in the doors, the roof, the frame. Some of these might have open pathways to the outside air, some might be closed off. They will all have different tendencies to condense water vapor in response to changes in the weather.
 
Have a look at this chart: Dew Point Chart (Degrees) - Simple & Fast

It only goes down to 10 C (same as 50 F). So let's say it's a miserable few days, cloudy, rainy, 50F outside, humidity is really high, 80 to 100%. No, your car is not air tight. Your trunk is not air tight. Maybe it will take 3 days, but at some point the inside of your trunk will also be 50F and 80% humidity. On the chart, where 10C and 80% meet, it says 6.7. That's degrees C, which is 44 F. So outside it stops raining, but it gets cold. It drops to 40F. It might take an hour or so, but your trunk lid will also eventually be 40F. Once the inside surface of the lid reaches 44, the water vapor inside the trunk will start condensing on it. If the outside air temp goes below freezing (below 32) and stays there for a while, then eventually the water beads that are condensing on the inside of the trunk lid will freeze there.

The thing is, if outside temperature and humidity changes are gradual, very gradual and slow, then the air in the trunk will follow those changes (with a huge delay, maybe a few days) and you won't actually ever get condensation. Now think of other compartments in the car, in the doors, the roof, the frame. Some of these might have open pathways to the outside air, some might be closed off. They will all have different tendencies to condense water vapor in response to changes in the weather.
Great explanation, thank you. We had a rapid cold spell, going from about 40 to 25 in just 2 days. That must be the cause. I’m gonna pop the trunk, shop vac the water beads, and maybe put in a small fan to keep the air moving, just as soon as it warms up (next week).
 
If the deck lid is closed, where's the "evaporated out" moisture going to collect? The bottom of the deck lid and the rear package tray are the highest points in the rear of that car. Which is where the condensate would collect, as those pieces of sheet metal are in direct contact with the cooling ambient air.

The silica gel cat litter is an interesting option. Just need a shoe box lid to spread it in.

Take care,
CBODY67
 
You can’t let snow sit on a car for any period of time, it will condense like crazy. I brush ALL the snow off DAILY. It will condense inside the roof also, but under the headliner and you won’t know the condensation is there, but it is. Same condensation under the hood, but it has some airflow.

A cloth car cover won’t do much. Any moisture under deck lid just wipe out with a towel first. Must open up the car when dry outside to let the car dry. Open doors or lower windows to let air circulate.

I have some good cars out under the stars. I cover with plastic when raining or snowing and take it off when dry or excessively windy.

Yes good condensation ideas above. Know the same thing happens inside the fuel tank so full that up on a car stored outside.
 
unless you are in a controlled stable climate you will get condensation as the temperature changes. Try a couple of boxes of Damprid it may help reduce the internal condensation.

IMG_7703.png
IMG_7703.png
 
Just FYI, damprid is almost 100% calcium chloride, which is cheaper if you buy it in the form of outdoor ice melter. You have to suspend or place the granules in a tray over a plastic tray or bucket to catch the slurry that results as water it taken out of the air. The slurry is very corrosive. The truck drivers that spread calcuim chloride on roads say that everything that touches the CaCl (pumps and even the pump motors) only lasts a year and turns to a pile of rust.
 
I didn't read every post, so I'm sorry if some of this is a repeat. If water can't get in, humidity can't get out. The same thing can happen under your car cover to a degree as well. The moisture from the ground and air can get trapped under it and it just sits there. Car covers are just dust covers really. They are best used in a garage. There are some SUPER expensive ones that work really well. The Damp Rid and silica beads are great ideas too. Might not be a bad idea to take the cover off and let it breathe after a rain or snow. Or even a warm day.
 
Just FYI, damprid is almost 100% calcium chloride, which is cheaper if you buy it in the form of outdoor ice melter. You have to suspend or place the granules in a tray over a plastic tray or bucket to catch the slurry that results as water it taken out of the air. The slurry is very corrosive. The truck drivers that spread calcuim chloride on roads say that everything that touches the CaCl (pumps and even the pump motors) only lasts a year and turns to a pile of rust.
Another decent, low cost option. I am going to investigate the silica cat litter choice. I am unsure of its corrosiveness.
 
For $380 you can buy a "car bag" - a weatherproof zippered bag that totally encloses your car. It comes with a desiccant packet of unknown material.

car_storing_step2.gif


About the only other thing you could do after the car is in the bag is flood the bag with nitrogen before you close it up.

While on the subject of outdoor car storage, I have been curious about these retractable / foldable car shelters, their availability seems limited, those that are available are expensive ($3k to $5k on amazon). If anyone here has one of these I'd like to know more about it.

foldable-garage-retractable-folding-car-garage-canopy-tent-213652.jpg
 
For $380 you can buy a "car bag" - a weatherproof zippered bag that totally encloses your car. It comes with a desiccant packet of unknown material.

View attachment 630490

About the only other thing you could do after the car is in the bag is flood the bag with nitrogen before you close it up.

While on the subject of outdoor car storage, I have been curious about these retractable / foldable car shelters, their availability seems limited, those that are available are expensive ($3k to $5k on amazon). If anyone here has one of these I'd like to know more about it.

View attachment 630491
Considering the increase in wind speed and increased possibilities of large of hail, not to mention tornadoes, I'd be wondering about the resistance of that covering to such? Plus how firmly it is anchored into the ground. I'm sure it would work well in some upscale venues, but weather "knows no boundaries".

Just some thoughts,
CBODY67
 
I looked at those clam shell units. The price was so low on what I saw it can’t be good quality. And the bigger it gets for a large car the stronger in needs to be to stay intact.

Were @darth_linux lives they get big amounts of snow, it would collapse that thing in no time with that flat roof design. Where he lives they have already had snow and been in the teens overnight. Real winter.
 
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Thank you everyone for the tips and advice. It's too late at this point to fill the gas tank, as the snowy hill I live on is impossible to navigate without snow tires and the gas station is at the bottom of said hill. I'm wondering if I should just remove the fuel filler cap to let it "breathe."
 
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