CONDENSATION on windows in winter

[Skinny_D]

When camping in the snow in winter, we obviously get a lot of condensation on the windows. We prepared for this by getting a nice dehumidifier and making sure we have inverter and battery capacity to run it. However, the windows themselves are a cold condensing surface and seem to do much of the dehumidification of the indoor environment.

What then is the best way to remove the moisture from the window AND the trough where the drips collect? I've tried sponges and paper towels but they don't seem to do a good job. Any thoughts on this?


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[pianotuna]

Skinny D wrote:


That's a great example with some good data. So, opening a window might help dry things out even if it's snowing outside! Crazy.

Absolutely.

vent and farthest window--electric heater near the window if possible. Adjust the vent/window until no more sweating.

[Monaramblee]

Have you tried drinking more?

[Skinny_D]

smthbros wrote:
If the air inside an RV is 60°F with 50% RH, then the dew point is near 40° and the specific humidity is near 39 grains per pound. If the outdoor conditions are 20° with 100% RH (ie it is snowing), then the dew point is near 20° and the SH is near 15.5 gr/lb. As indoor air is exchanged with outdoor air, the indoor air will become drier.
FYI, there are online psychrometric calculators for any one interested doing their own.

That's a great example with some good data. So, opening a window might help dry things out even if it's snowing outside! Crazy.

[smthbros]

If the air inside an RV is 60°F with 50% RH, then the dew point is near 40° and the specific humidity is near 39 grains per pound. If the outdoor conditions are 20° with 100% RH (ie it is snowing), then the dew point is near 20° and the SH is near 15.5 gr/lb. As indoor air is exchanged with outdoor air, the indoor air will become drier.
FYI, there are online psychrometric calculators for any one interested doing their own.

[Gdetrailer]

Skinny D wrote:

Gdetrailer wrote:

As I mentioned, there is built in "drains" in the windows, they are hidden from view, moisture collects on the window surface then rolls down to the bottom.. At the bottom of the window there is a couple of well hidden drains that send the moisture to the outside of the frame.

Take a close look at the outside of the window frame, you should see two plastic "covers" at the bottom of the frames.. Those are the drain points.

You should not have to "mop" the moisture at the bottom of the window frame unless the drains are clogged..

Drains are there to help redirect any moisture that gets past the window slide gaskets in heavy rains..

Won't hurt to mop it but not really needed..

That's some info that I needed! I was wondering about that... whether there was some weep holes in the window. Of course, that sacrifices insulation but helps get rid of the moisture. See pic below. I went right out and inspected and that's what I found. I presume that's the weep hole.

In that case, I'll just get one of those little bathroom squeegees and squeegee the moisture straight down toward the trough at the bottom. Then it can go out the holes and the cold window is primed to condense additional moisture. I'll run the dehumidifier when convenient as well.

As a side note, I'm not sure that heating up the air actually dries the air (in pretty sure it doesn't), but it does help the dehumidifier work more efficiently. Hotter air has a large capacity for holding moisture in vapor form. So the meter reads a lower %RH just because the capacity of the air to hold moisture went up... not because there is less moisture in the air.


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Yes, that is a weep hole or drain, they used to put a little plastic cover over those.. Cover often got sun baked and fall off over time..

Some windows which are designed to be able to be flipped so the opening window opens the opposite direction will have additional weep holes on the top of window.. Those top holes should have a plug or at least the same style cover.. Otherwise rain water can run right into the top of the window..

[Skinny_D]

Gdetrailer wrote:

As I mentioned, there is built in "drains" in the windows, they are hidden from view, moisture collects on the window surface then rolls down to the bottom.. At the bottom of the window there is a couple of well hidden drains that send the moisture to the outside of the frame.

Take a close look at the outside of the window frame, you should see two plastic "covers" at the bottom of the frames.. Those are the drain points.

You should not have to "mop" the moisture at the bottom of the window frame unless the drains are clogged..

Drains are there to help redirect any moisture that gets past the window slide gaskets in heavy rains..

Won't hurt to mop it but not really needed..

That's some info that I needed! I was wondering about that... whether there was some weep holes in the window. Of course, that sacrifices insulation but helps get rid of the moisture. See pic below. I went right out and inspected and that's what I found. I presume that's the weep hole.

In that case, I'll just get one of those little bathroom squeegees and squeegee the moisture straight down toward the trough at the bottom. Then it can go out the holes and the cold window is primed to condense additional moisture. I'll run the dehumidifier when convenient as well.

As a side note, I'm not sure that heating up the air actually dries the air (in pretty sure it doesn't), but it does help the dehumidifier work more efficiently. Hotter air has a large capacity for holding moisture in vapor form. So the meter reads a lower %RH just because the capacity of the air to hold moisture went up... not because there is less moisture in the air.


Click For Full-Size Image.

[ktmrfs]

our solution in winter coast camping in high humidity is to have a 30+ pint 120V compressor driven dehumidifier running. It will usually pull about 5 gallons of water out in the first 12hrs the 3-5 gallons/day. Keeps the condensation minimal. The other thing we have done is go to tap plastic and have them cut some plastic to put over the non opening windows to make them a poor man's double pane. More expensive than plastic film which also works, but holds up better and helps in the summer for mimimizing heat gain.

[JBarca]

Skinny D wrote:

snip...

The indoor humidity is about 48% to 62%, but I don't have a meter that gives the 24 hr high/ low.

I should clarify the reason that I care. It's not the cosmetics of beads on the window and it's not concern for damage to the TT. We are in the snowy mountains for skiing, and we have lots of wet gear at the end of the day that needs to dry out before the next morning. I'm concerned that the accumulated moisture on the window will just be eventually returned to the air and my clothes/boots won't dry as well (starting a ski day in wet gear is not ideal). So, I'd like that window moisture to be discarded somehow or redirected to the dehumidifier.

The window covering option seems best (creating double pane windows) but this seems permanent? Do you remove and re-apply it each year for the different seasons? Is there no "super sponge" option for wiping windows and collecting that condensate?

If you go the shrink wrap option on the windows, yes, you do remove it annually "if" you want those particular windows to open.

We leave ours on for as long as we can. The weather in the mid-west is totally unpredictable. The plastic film helps on spring campouts, so leave it on. Come summer, the weather can go super hot, high humidity overnight it seems. If the film is still on by then, and we use the AC, we leave the film on. It helps keep the AC air in and not let so much heat in. When we go boondocking under tree cover in the summer, then we want the windows open so the film comes off which is quick to do. It does take time later to clean off the little left over tape residue. If you never want to open a window, you can leave it on as long as you want. That said, after about 3 years the tape may start coming loose or you knocked it and it broke loose.

The plastic film greatly helps keep the heat in, during the cooler weather, and it stops the sweat. If you do a lot of cool weather camping, the heat savings and dry windows makes it worth it for us. The cost of the film, is about $13.00 for our 32 ft camper. And we do not use all of it from the 2 kits. It does take time to put it on though.

High humidity does create mold and rusted screws/metal in the camper attic. It is something to be concerned about if you plan on keeping the camper a long time. Just 2 people camping in those conditions is enough of an issue for the attic molding/rusting problem to be there as the years go by. Adding attic vents, does help this and lowers the camper inside humidity. Trying to dry out wet heavy cloths makes it harder to keep the humidity down. For sure, try and help the problem with high humidly.

On the window frame drains, not all camper windows have drains. If the window opens, then yes odds are high it has drains from leaking water from the seals on the opening window. If you have windows that do not open, like a big picture window, entry door windows or some slide room end wall windows, odds are high, that style window does not have drains.

Good luck and let us know what you come up with.

John

[spoon059]

OP, sounds like you don't have electricity but if you do I might suggest electric heaters. They will dry the air as they heat, helping with condensation. We don't cold weather camp as often now tat we have small kids, but used to winter camp all the time. Our little 22' camper only needed a single 1500 watt heater to keep cozy and dry.

[time2roll]

JIMNLIN wrote:
...so I bough a 2nd bigger one and finally after 4 months we had finally fixed the sweat issue for this particular rig.

Possibly we underestimate the size of the problem in this small enclosed space. Easiest to justify purchasing the smaller less expensive model and see how it goes. Apparently it is best to go a bit larger with more features.

[JIMNLIN]

The window covering option seems best (creating double pane windows) but this seems permanent? Do you remove and re-apply it each year for the different seasons? Is there no "super sponge" option for wiping windows and collecting that condensate?

The wife would wipe a window but a hour later she would have to do it again.
I made mine removable with 1/4" X 3/4" long hex head screws and stored them in the big closet across the front of the trailer.
Never used them again as we had our belly full of winter issues in a camper. This is COE lake country around here so not much winter camping with most good campgrounds closed.

Also open flame with LP like the stove/oven creates more moisture in the air.

AS I stated above their is no single silver bullet that kills condensation in a RV trailer. Now if they were all the same as my unit was and had the same work everyday schedule...then what I did would work for all.
Like everyone else your gonna' have to try different scenarios and see what works for your unit at that location. Good luck 🙂

[Gdetrailer]

Skinny D wrote:
Thanks for all the experienced folk who weighed in here.

The indoor humidity is about 48% to 62%, but I don't have a meter that gives the 24 hr high/ low.

I should clarify the reason that I care. It's not the cosmetics of beads on the window and it's not concern for damage to the TT. We are in the snowy mountains for skiing, and we have lots of wet gear at the end of the day that needs to dry out before the next morning. I'm concerned that the accumulated moisture on the window will just be eventually returned to the air and my clothes/boots won't dry as well (starting a ski day in wet gear is not ideal). So, I'd like that window moisture to be discarded somehow or redirected to the dehumidifier.

The window covering option seems best (creating double pane windows) but this seems permanent? Do you remove and re-apply it each year for the different seasons? Is there no "super sponge" option for wiping windows and collecting that condensate?

As I mentioned, there is built in "drains" in the windows, they are hidden from view, moisture collects on the window surface then rolls down to the bottom.. At the bottom of the window there is a couple of well hidden drains that send the moisture to the outside of the frame.

Take a close look at the outside of the window frame, you should see two plastic "covers" at the bottom of the frames.. Those are the drain points.

You should not have to "mop" the moisture at the bottom of the window frame unless the drains are clogged..

Drains are there to help redirect any moisture that gets past the window slide gaskets in heavy rains..

Won't hurt to mop it but not really needed..

Damp clothing/gear however can be an issue and makes the inside humidity more of a problem to deal with.

Keep in mind, if it wasn't for the windows collecting moisture, EVERYTHING ELSE would condense and collect the moisture.. It is not unheard of to have moisture dripping from ceiling or running down the walls and that is what you want to avoid.

Dehumidifiers can only help so much and they tend to not work effectively once the ambient air temps drop below 70F due to freeze ups of the condensing coils.. Granted most expensive dehumidifiers have a freeze sensor but when that trips it is too late and you end up with a solid block of ice on the coils blocking the fan. That ice has to melt so the compressor turns off and the fan runs until the ice melts and falls off the coils.. Wasting a lot of time and electricity..

To myself, it seems if the clothing and gear is the big issue then you need a way to dry those items before putting into the RV for the night.. RVs typically are not designed to cope with huge amounts of moisture. RV washer/driers tend to be pretty small and inefficient for drying..

[pianotuna]

JIMNLIN,

Sweating is because the surface is below the dew point temperature.

[Guy_Roan]

I