Condensation / Humidity Woes!

[Zigidachs]

Condensation and Humidity! The scourge of Airstreams.

How to control condensation and humidity in this beautiful aluminum cocoon?

In storage, we use Damp Rid units. On the road we use an electric powered dehumidifier. We rarely shower in our unit. However when the temps dip outside--only into the 40's e.g., we always experience window condensation which we perceive as a threat because of the volume of accumulated moisture and where it might drain! ....behind the insulation!

When we have camped in much lower temps, the condensation / moisture problems are compounded. How do winter campers handle these problems?

Thanks to all who can enlighten us. Zigi

[dkottum]

Any Rv that has a watertight shell will have condensation problems, as well as many stick built houses. Modern houses solve the problem with air exchangers, which may not be practical for small RV's such as Airstream

But you must ventilate, even though there will be heat loss. Ventilate according to the activity and number of people. For example cooking produces lots of moisture, showers some, and of course breathing some.

We find by cracking the bedroom roof vent an inch at night and opening the shower and toilet vents, we have no moisture problems (in the dry Southwest). Using the range vent whenever cooking, plus a roof vent or two will do the trick.

Experiment, but ventilation is the answer.

doug k

[Protagonist]

Originally Posted by Zigidachs

When we have camped in much lower temps, the condensation / moisture problems are compounded. How do winter campers handle these problems?

Low-tech, low-cost method… Catch any condensation that forms before it drips where you don't want it. Roll up a towel and place it against the bottom edge of the window frame. When the towel gets too wet from dripping condensation, wring it out in the galley sink and replace it. If the window frames are too narrow to hold a towel, you can do the same with paper towels, except throw them away (in a bucket) and replace them with dry paper towels when they get too saturated.

[perryg114]

Condensation is an issue but in most trailers, more moisture gets in from leaks than anything else. Ventilation is important as the others have said. De-Humidifiers are an excellent idea. Running the furnance with some ventilation is a good idea. The other day I ran the furnace and the AC for a while to dry things out. I will probably get a dehumidifier and drain it into the shower at some point.

Perry

[Protagonist]

Originally Posted by perryg114

Condensation is an issue but in most trailers, more moisture gets in from leaks than anything else. Ventilation is important as the others have said. De-Humidifiers are an excellent idea. Running the furnance with some ventilation is a good idea. The other day I ran the furnace and the AC for a while to dry things out. I will probably get a dehumidifier and drain it into the shower at some point.

Condensation happens when the temperature of a surface is lower than the dew point of the surrounding air. You can:
1 - heat the glass surface so it's warmer than the air's dew point;
2 - dry the air to lower the air's dew point;
3 - move the air so that individual water vapor molecules don't stay in contact with the glass for water to condense.

Interesting point, heating the air doesn't lower the dew point of the air, and you'll still get condensation as long as the outside of the trailer is cold, even if the inside air temperature is sweltering hot. Look at a glass of iced tea in the summer; same principle, hot air plus cold glass equals condensation. My previous suggestion was the same as putting down a coaster under a glass of iced tea; if you can't stop the condensation, catch it.

[dkottum]

Trouble with catching condensation as a solution, is that in will form inside the shell due to all the penetrations for fixtures, window frames, vents, plumbing/electrical runs, and such.

It is most important to ventilate the moist air to the outside before it has a chance to collect on exposed and hidden surfaces.

doug k

[Protagonist]

Originally Posted by dkottum

Trouble with catching condensation as a solution, is that in will form inside the shell due to all the penetrations for fixtures, window frames, vents, plumbing/electrical runs, and such.

It is most important to ventilate the moist air to the outside before it has a chance to collect on exposed and hidden surfaces.

doug k

True, as long as the air coming in to replace it is drier than what he's venting out. But I figured there would already be plenty of responders saying, "Ventilate, ventilate, ventilate" and not too many others giving other alternatives.

[Smartstream]

Sopping up condensation dripping off the windows is kind of like putting a bucket under a leak. Ventilation will "fix" the leak before it drips in the bucket. We lived on our boat for ten years and vents open at sea in the rain will keep the boat dry inside.

[Protagonist]

Originally Posted by Smartstream

Sopping up condensation dripping off the windows is kind of like putting a bucket under a leak. Ventilation will "fix" the leak before it drips in the bucket. We lived on our boat for ten years and vents open at sea in the rain will keep the boat dry inside.

But when I lived in a trailer in northern Maine 50 years ago as a kid, no amount of ventilation would stop the condensation when the temperature inside was above freezing and the temperature outside was below freezing.

Under those conditions, ventilation alone is not enough.

[perryg114]

You are correct. Heating the air in the trailer just allows water to evaporate and get it hot enough in there so the compressor on the AC runs to get rid of the water vapor. Also the furnance was right below where I just repaired a leak and I knew the insulation was wet there. Running the furnance helped dry the soaked insulation above it. I also had the bathroom vent fan running. The stove vent was the source of the recent leak and it has been removed for the time being.

Perry

Originally Posted by Protagonist

Condensation happens when the temperature of a surface is lower than the dew point of the surrounding air. You can:
1 - heat the glass surface so it's warmer than the air's dew point;
2 - dry the air to lower the air's dew point;
3 - move the air so that individual water vapor molecules don't stay in contact with the glass for water to condense.

Interesting point, heating the air doesn't lower the dew point of the air, and you'll still get condensation as long as the outside of the trailer is cold, even if the inside air temperature is sweltering hot. Look at a glass of iced tea in the summer; same principle, hot air plus cold glass equals condensation. My previous suggestion was the same as putting down a coaster under a glass of iced tea; if you can't stop the condensation, catch it.