Condensation in campers and how to avoid it!

[Victorian]

Every year I'm getting calls from customers asking for advice on how to prevent condensation in a DIY / custom camper in winter condition.

I experienced this too on my personal camper. This is of course a WTH moment first, but when you start looking closer into thermal dynamics and understand how condensation forms, it all makes sense and can easily be avoided.

1. it's important to remember that any type of "insulation" that is in direct contact with the outside walls (cold surface) will act as an insulated barrier not giving the camper walls a chance to warm up. Key is to have air flow between the cushions/mattress. Ideally, although not easy to accomplish, is getting warm air flow from the heating system behind the "insulating" layers. At the same time, it's also important to avoid "dead air pockets" where moisture is trapped (storage hatches,behind cabinets etc). With all of this in place there will be no condensation on the panels or the pultrusions. This means, if the bed mattress is tightly fitting and won’t allow air flow around the edges and underneath, you will see condensation and a wet mattress for sure. The mattress acts like an insulating layer. The Goodside Bedslat system by Expedition Upfitter would be an excellent choice to help with this.

1. • Heating source: We had great success with diesel heaters. These recirculate the interior air and produce a “dry “ heat. The air flow of these can be guided into the “right” places with ducting (storage hatches, entry ways etc).
   • Ventilation: I’m not a big fan of any forced ventilation contraption that is mounted on the roof… Not only do they ad a lot of overall height, most of them also don’t have the track record in reliability… Instead, I would rather open the windows for cross airflow and work with small efficient and quiet portable fans.

1. • Another important detail to know when it comes to condensation: Because campers/RV's are such a small space with relatively minimal materials to absorb moisture (through breathing,cooking,showering etc) it is more likely that water droplets form on surfaces that are cold. For example: we have a huge walkthrough between the camper and drivers cab in our Ford Transit. We have never seen condensation anywhere inside the camper (except on the window frames), the drivers cab on the other hand gets hammered with water! What I want to say: the moisture will also find the weakest point to collect. In our case we can't avoid it, just minimize it with a heavy curtain. Bottom line is: warm air flow and avoiding cold dead air spaces. You can never have enough warm airflow!

1. • Here is another thing I learned right in the beginning on my first TC camper 8 years ago. Back then, I only could afford a mister buddy gas heater. I had a window cracked at night and used a warm winter sleeping bag. I was very comfy that night. In the morning I had condensation in that camper you wouldn't believe. It was dripping of the ceiling! Needless to say how disapointed I was. Shortly after, I installed a diesel heater. What a difference!!!! I also learned that condensation forms at the dew point . This means your camper is most likely to form condensation if it gets too cold inside. When we go out in our camper, we only use summer blankets (year around). This forces us to turn the heater on instead of "bundling up".

Take away:
Allow for plenty of warm air circulation between seat cushions/mattresses. Remember the dew point and keep the interior warm with circulating air flow.

Hope this will be useful to some of you. Cheers

 

[simple]

I've had good luck controlling condensation in my camper taking a cue from the automotive and marine industry. In a nutshell, I lined my walls with a fuzzy fabric.

The fuzz holds really small water droplets (can't be seen compared to condensed water that pools together like the inside of a cold window) that evaporate quickly when warmed air passes over the surface.

If when I build out a composite camper, I might try making removable interior panels with fuzzy material on the surface. If the fuzzy material gets dirty / mildewed I'll swap them out.

The other thing that helps is to not store water absorbent material in the camper in the winter when not in use. We remove our camping pad mattresses, bedding, clothes etc when we return from a trip and run the heat for a while to make sure the interior is really dry.

Regarding condensation and air flow, when cold incoming air warms up, it now has the capacity to hold more moisture like a sponge. The warm air will absorb moisture and then when it exits the space it takes moisture out with it and so continues the cycle of heating and drying.

 

[AbleGuy]

He’s definitely right about the preference for a diesel fuel heater

It’s well known that, if you’re using propane for heat and cooking, you’re going to be generating quite a bit of moisture as a byproduct

But also, if there are any large mammals hanging out inside your small camp box, their exhalations also are unavoidably going to generate moisture

In the past in our campers we’ve used those super absorbent camping bath towels to wipe down wet surfaces in the morning (and then dried them out by putting them on the dashboard while driving)… also (a bit more old school) used school blackboard erasers for wipe downs!

 

[Gravelette]

Yes, the carpet like material on the walls and ceiling of my small Casita travel trailer does a great job of keeping condensation at bay. It somehow doesn't retain moisture, never has had mildew, etc. I do like having the ability to crack open the overhead fan cover. In my mind I see it letting warm, moisture heavy air escape. Of course like most of us I'm not qualified to talk about thermodynamics so it could be imaginary. The windows are another thing and don't need much encouragement to drip. I have both propane and electric heat. The propane combustion is entirely separate from the interior air so it doesn't increase condensation.

 

[rruff]

I do like having the ability to crack open the overhead fan cover. In my mind I see it letting warm, moisture heavy air escape.

True, humid air is lighter than dry air.

Having an unvented heat source (Buddy, Camco, stove, etc) is the biggest culprit, with 1 lb of propane combustion creating 1.6 pounds of water... no joke. Human respiration creates ~0.10 lbs/hr, so that can get significant also.

Diesel heaters are always vented and decent ones are quite cheap, so that seems like a good way to go. I don't use any heat at all, but I don't camp in "real winter" either... in winter I head to the southern CO river valley.

Another thing to note is that resting humans give off about 100W of heat, and a well insulated camper will warm up ~20 F just from that.