Condensation - how bad is it really ?

[leefl]

Originally Posted by BamaBob

Absolutely the best solution to humidity issues I have found in all my years RVing!


amazon Eva Dry

And the best part? no sloppy dessicant to spill (don's ask me how I know about that )

Hmmm, interesting.
So you just plug it in to 'renew' which presumably heats the crystals to release the moisture.
I guess I'd need spares to allow for swapping out the full ones, but does seem tempting.
I could probably just plug them in outside on an extension cord to renew while camping.
Where do you keep them ? Do you just leave them free-standing, or do you have some other setup ?

[leefl]

"Works in areas up to 333 cubic feet"

Well our 5er is 8 feet wide (without slides), 32 feet long, and has an average ceiling height of I guess 8 feet, so even without the slide area that's 2048 cubic feet.
adding just the sofa/dinette and bunk slides, that's another 280 cubic feet at least (likely plenty more), so total over 2300 cubic feet

so they're saying I'd need 7 of them !
At least for the equivalent of me leaving the 2 damp-rid containers in the open.

I am tempted to see if one of these performs similarly to a container of damp-rid.
If I did get some I'd likely get the larger Eva-Dry E-500 and leave one in the bathroom (when not showering), one in the bedroom, and at least one in main slide-out area, both when camping and when in storage.

[Hclarkx]

Originally Posted by rockfordroo

............ Note that contrary to popular belief, running the furnace will NOT increase moisture in the TT. While the combustion of propane does create water, this is vented outside of the TT.

While running the furnace does not increase or decrease moisture in the TT, it does warm the inside air so it can hold more moisture in suspension, at least until there are nearby cold surfaces (windows) for it to condense on as happens at night. We've found that when the air inside the TT is warm due to sun or heating from the furnace we can often circulate cooler outside air into and through the TT taking that warm moist air out. This only works were the cooler outside air is dry and does take some timing, but has served us well. Judiciously using the exhaust hood when cooking and wiping the shower down (and putting that towel outside to dry) also help.

Interestingly, I was changing failed LED ceiling lights and found copious moisture behind two of them. It was on the thin plywood sheathing that is between the styrafoam filler and the roof skin. There was as yet no mold (the TT was less than a year old). Apparently the cool roof was attracting this moisture through holes in the light fixture because I could find no roof leaks. This happened with no signs of excess moisture anywhere else in the TT. I got very concerned and have since been even more diligent about keeping moisture out. I've removed those light fixtures to check for moisture twice since and found none.

[Rwgrigg]

I bought one of the cheap solar panels and connected it to one of the computer type 12vdc 6" muffin fans which I set in my trailer. These don't draw much current and doesn't take much of a solar panel to power it. Because of cloudy days, the fan did not run everyday. But it running every other day or so seemed to help keep the condensation down and the mildew out. I used this in my boat which has a cuddy cabin and was closed up in the wintertime when the condensation seemed to be greatest considering the weather here in Southeastern Virginia. You could use one of the small 12 motorcycle or lawnmower batteries and use the panel keep a "trickle charge" on it with the panel if you needed the fan to run more. Just remember to mount the solar panel facing South to get the most exposure from the sun (when its out). I did also put a container of Damp-Rid in the boat for added measure. Don't seem to need it in the trailer. On the trailer I keep the roof vents cracked to help vent the air out.

35' Heritage Glen Camper Trailer

[BamaBob]

Originally Posted by leefl

Hmmm, interesting.
So you just plug it in to 'renew' which presumably heats the crystals to release the moisture.
I guess I'd need spares to allow for swapping out the full ones, but does seem tempting.
I could probably just plug them in outside on an extension cord to renew while camping.
Where do you keep them ? Do you just leave them free-standing, or do you have some other setup ?

Yep it works great (and if your rig has a washer and dryer get one dedicated to set inside your washer (just remove before use )

One in the Bathroom will take care of that area + the bedroom if you leave the doors open. One more up near the front of the coach and you are more than covered! We also keep one in the basement as well.

We only have the 4. They "fill up" at variable rates and we have found setting them outside and plugging them in returns the crystals to a dry state in @ 5 hours.

[Hclarkx]

Just read in another forum on this subject .... when the RV is warm and the moisture is in the air (not on the windows), run the A/C for 15 minutes to take out a lot of moisture. I'm thinking maybe even warm the place up a bit with the forced air heat, to 70 or more, then run A/C for 15 minutes. Has anybody tried this?

[bikendan]

Just realize that many that have responded, don't own a hybrid TT and don't know the unique issues of hybrd condensation.
Using PUGs and Reflectix, along with allowing for air movement, have cured condensation in the canvas tent ends, for most owners.

[Susquatch]

Archicamper has it correct. But I feel inclined to provide more information to help everyone understand their individual issues. I'll try not to get too technical.

Air holds different amounts of water depending on the air temperature and pressure. Hot air holds way more water than cold air does.

Relative humidity is always associated with a given temperature and pressure. A measurement of 75% relative humidity simply means that air at that specific temperature is holding 75% of the water that it is capable of holding.

If you warm the air without adding or removing any water, the relative humidity will go down. If you cool it, the relative humidity will go up. If you keep cooling it, the relative humidity will keep going up until it becomes fully saturated holding 100% of the water it can hold at that temperature. This is called the dew point. It is called that because further drops in temperature will cause any water it can no longer hold to condense in the form of rain fog or dew.

Adding cold outside air to a warm enclosure usually lowers the humidity. Since the enclosure is warm, the air in it holds more water than the incoming cold air usually does. Maintaining the temperature with a furnace will automatically lower the humidity as the cold new air warms up. This is why the air in your home is usually so dry in the winter.

In the summer, the opposite happens. That warm air is cooled as it mixes in a cooler room and the humidity goes up. This is when that air conditioner kicks in to do something magic. Air conditioners that are properly set up cool the air so much as it passes through the evaporator coils that the air in the coils drops past it's dew point and the water condenses out. You can easily see this moisture dripping from window units and under your car. After leaving the airconditioning unit, the air warms back up and therefore, it's relative humidity dives. A dehumidifier works the same way but is specifically designed to remove water without lowering the overall air temperature like air conditioners do.

As other posters have mentioned, water also gets in the air and raises the humidity when we breathe, when we sweat, when we boil water, when we take a hot shower, when wet clothes dry out, and when we cook on a gas or propane stove (the fuel actually combines hydrogen in the fuel with oxygen from the air forming H20 which is water) to mention just a few sources.

Also, as some posters have mentioned, air that is holding a lot of water will cool as it passes cold surfaces (like that canvas pop-out wall folks are concerned about) and water will condense on the wall.

Trapped air under a mattress or behind insulation will also lose its water as it cools. Any insulation will result in a large temperature differential between the outside surface and the inside surface of the insulation/mattress. That's what insulation is supposed to do! But if humid air is trapped and gets colder than its dew point behind that insulation, water will condense out. The trick is to prevent significant volumes of air from being trapped in these areas. Solid (closed cell) foam is better than spongy foam.

Hopefully understanding the nature of humidity and condensation will help members understand and address their individual situations. If you hunger for more, get a good book on heating and airconditioning engineering and take some time to study a psychrometric chart.

In the meantime, here are a few tips:

If you have an electric hookup, dehumidifiers work great with well sealed enclosures, and electric heaters work especially well with a little fresh air exchange.

Furnaces with air exchangers also work well, but don't use a fuel fired standalone space heater.

Water absorbers and desiccants also help in marginal conditions, but usually can't handle extremes.

Minimize water vapour sources.

Managed air exchange (vents, windows, even air leaks) can be a great asset IF you understand the nature of "relative" humidity.

A good air conditioner can also be used to reduce humidity even when it's cold out! In fact, your car probably uses its air conditioner to dry the air out in defrost mode even in the winter!

Cheers!

[leefl]

Excellent post susquatch

[Disa]

Originally Posted by howie70

When I had my hybrid I didn't have a lot of condensation on the bunk ends above the beds, mine was under the mattress. I tried a lot of different things and the only thing that stopped it was cutting the 1" foam insulation (like you get from Lowes in 4'x8' sheets) and putting it under the mattress.

Thanks for this. I made a cover with two space blankets (till I buy a Pug) which fixed the condensation on the roof of the tent ends, but very wet underneath the bed.
So we bought reflectix and I put it underneath the bed, but that didn't not fix the problem. The next idea was to try and put the reflectix under the outside of the platform...
I was not too excited about this method, and so, I am happy to hear about the foam underneath the bed. Perhaps the reflectix was just not thick enough. Right now I am lifting and drying the mattress every other day with the fan. A pain for sure.
Thanks again.

[ROCAMPER]

Just wondering. Do the heated mattresses help with keeping condensation down under the mattress? We camped in very cold weather last October and had lots of condensation on the tent ends. I didn't notice under the mattress, but I never really looked. We did have the heated mattresses on though.

[Archicamper]

If the mattress heater raises the temperature above the dew point there will be no condensation.


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[sherman12]

Though I have a class A, DW and I always burn a candle in the rig, even during warm summer days to help prevent the damp feeling the can set into a RV, especially at dusk. Leave one burning all night to for the exact reason of burning up the dampness during cool summer nights while sleeping with the windows open. Since there is only the two of us we don't fear a fire or anything dangerous with the candle burning.

[howie70]

Originally Posted by Archicamper

If the mattress heater raises the temperature above the dew point there will be no condensation.


Sent from my iPhone using Forest River Forums

Wouldn't the heat of the mattress meeting the coldness of the bunk end platform cause more condensation? We always had the condensation right under where we was laying. Nothing around the edges of the mattress, just where our body heat was.

[howie70]

Originally Posted by Disa

Thanks for this. I made a cover with two space blankets (till I buy a Pug) which fixed the condensation on the roof of the tent ends, but very wet underneath the bed.
So we bought reflectix and I put it underneath the bed, but that didn't not fix the problem. The next idea was to try and put the reflectix under the outside of the platform...
I was not too excited about this method, and so, I am happy to hear about the foam underneath the bed. Perhaps the reflectix was just not thick enough. Right now I am lifting and drying the mattress every other day with the fan. A pain for sure.
Thanks again.

You're welcome! Hope it helps. The rigid 1" foam can be a little bit of a pain to store when traveling, but it was the only thing that worked for us to stop the condensation.

[Flybob]

The condensation on the bed platform surface ( which then wets the bottom of the mattress) comes from the moisture from your body penetrating the mattress and condensing on the cold platform. The best way to prevent it from occurring is to have a moisture and temp barrier between the mattress and the cold bed platform. A sheet of foam insulation will keep the moisture from reaching the cold bed platform and keep the bottom of the mattress warm enough not to allow the moisture to condense. This can happen in a pop-up, hybrid and even in a larger TT or 5er with an unheated basement beneath the bed. Many times this moisture goes unnoticed until mold forms and starts to smell. You can also get moisture between the head of the bed and the RV wall if the mattress touches the wall. The easiest way to cure this is to place a small pool noodle between the mattress and the wall to allow for circulation.

[Archicamper]

Originally Posted by howie70

Wouldn't the heat of the mattress meeting the coldness of the bunk end platform cause more condensation? We always had the condensation right under where we was laying. Nothing around the edges of the mattress, just where our body heat was.

I don't think this is the case. Heat typically is your friend. I would venture to say that the center of the mattress is the coolest spot. The mattress does a pretty good job of insulating you from the outside which is pretty much right underneath you. The edges stay warmer from the air inside the camper. Also there is some air movement around the edges of the mattress that will also have a drying effect.

[bitNine]

I remember the first time I was awaken after a cold night in the tent camper, thinking I was being peed on.

[doc73]

That's what happens when you assume the kids walked the dog when he was crying at the door.... OH YEAH.... Right, condensation!