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Old 01-10-2021, 02:01 PM   #1
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Humidity: Where does it come from?

We keep our Sonoma (Evo) 220RBS travel trailer at our home, doors, vents, windows, shut.
Since we live on the ocean coast, the humidity is about 95% or more, 95% of the time.
We have a small dehumidifier inside that we empty about twice a week. About a cup of water in about a week. Other than emptying the dehumidifier, we do not open the doors, etc. We close the door quickly when entering to empty the unit.
Solid vinyl floor, laminate exterior, carefully inspected joints.


Question: Where is this water coming from?

A) From the plumbing traps in the sinks and toilet
B) From leaks in the ‘envelope’ (windows/doors/vents/etc.)
C) Sucked through the skin of the trailer
D) From the ‘weep holes’ in the windows

Any other ideas?

Thanks in advance,
Rennie
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Old 01-10-2021, 02:18 PM   #2
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Rennie, these things are far from air tight. Moisture from outside will always get in, just like your house. Thus the need for a dehumidifier. My TT in NJ, which is covered, is always near 70% humidity inside without a dehumidifier running, with ambient humidity ranging from 99% at night, to 45% during the day during winter.
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Old 01-10-2021, 02:21 PM   #3
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All of the above, plus, since you live near the ocean, it's in the air.
Everytime you open the door to empty the dehumidifier, warm moist air will rush in.
Living in a humid climate (Houston, TX) we use a big bucket of DampRid. That eliminates having to empty a dehumidifier. We do check on it about once a month and replace when necessary.
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Old 01-10-2021, 02:39 PM   #4
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If your dehumidifier has a full timer drain option, it is very easy to install a small drain through the floor in a hidden corner and you will not have to empty it. You can use the shower drain, but most dehumidifiers are made in China and they can generate some rust in the drain water which will stain the shower floor.
As for the humidity in an RV, it is no different than your home, it is not hermetically sealed.
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Old 01-10-2021, 02:43 PM   #5
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1. Your RV is not air tight.

2. Atmospheric Pressure is 14.7 psi.

3. Your relative humidity is 95%.

4. Daily ambient heat and nightly cooling produce condensation.

5. The presence of a human being aspirating inside the RV adds to moisture in the air.

6. As soon as the door is opened an "air exchange" happens.

Your dehumidifier seems to be doing it's job. If you're concerned about humidity inside I suggest you get a weather station with a remote temp/humidity sensor and place the sensor inside to track the actual relative humidity inside the RV.
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Old 01-10-2021, 03:03 PM   #6
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Whatever you do, don't buy those Eva Dry things, total waste of money. Two big ones I bought make no dent on inside humidity. You plug them in when the get saturated to dry them out. I've done several before and after weigh-ins of units. I've calculated they removed about 4 tablespoons of water from air.


Here, it is too cold to run dehumidifier now, so you just reminded me to open door and air it out. No ocean humidity here at present, and 44% R.H. Already fell from 67% to 57% in 15 min inside the TT.
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Old 01-10-2021, 03:12 PM   #7
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I don't get concerned about humidity in the camper based on my experience with my boats which sit in the water or on cradles within feet of the water 24/7 their entire lives. Ventilation is a must, not sealing. I use solar vents and louvered companionway hatches to keep air moving thru the boat. The stainless steel fittings on the boats in salt water need some attention but that's about it. I know guys who've used those buckets of damp-rid stuff with no more success than mine.

I'm not storing my camper in the same conditions but I still keep it ventilated with the covered roof hatches open and the cabinets open.

I ran a dehumidifier in my last house which drained directly into a floor drain. No reason you can't run one thru the floor of the camper -- heck, just drill a hole thru the floor where you need it. Plug it when not in use. Easy peasy.

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Old 01-10-2021, 03:22 PM   #8
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Quite simply your RV breaths. Like others have said your RV is not air tight. This is very good thing. If it were air tight it would expand out like a ballon when it warmed up and collapse when it cooled down.

So, heat up = exhale, cool down = inhale. When it inhales it sucks in damp/humid air. Some of that humidity hangs out in the air inside the RV while some of it is absorbed into the RV soft surfaces such as bedding, carpets, towels, mattresses, etc.

Which, BTW, is why when you put your RV up for the season you should lift your mattresses (use soccer balls, etc) so air can circulate and hopefully get rid of more of that pesky moisture. Hint, mold loves living in 50% or more relative humidity.
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Old 01-10-2021, 03:43 PM   #9
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Quote:
So, heat up = exhale, cool down = inhale. When it inhales it sucks in damp/humid air.
Good analogy.
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Old 01-10-2021, 03:44 PM   #10
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Originally Posted by NJKris View Post
Whatever you do, don't buy those Eva Dry things, total waste of money. Two big ones I bought make no dent on inside humidity. You plug them in when the get saturated to dry them out. I've done several before and after weigh-ins of units. I've calculated they removed about 4 tablespoons of water from air.

Those "things" are designed for small spaces and fairly well sealed. I use one in a safe where I keep my "unmentionables" (at least unmentionable here)

Works pretty good to keep humidity low enough to prevent rust and mildew.

Unfortunately it takes almost 48 hours to really dry them out while plugged in.
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Old 01-10-2021, 03:50 PM   #11
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Dang, now you’re on the list...right after me.
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Old 01-10-2021, 03:50 PM   #12
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I imagine they would be fine for a safe or something, but their 'up to 500 cubic feet' claims are absurd. I bought 2, as my trailer is much less than 1000 cubic feet. And yes, they have to be dried out over a couple 12-16 hour periods.
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Old 01-10-2021, 03:51 PM   #13
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Originally Posted by Chuck_S View Post
I don't get concerned about humidity in the camper based on my experience with my boats which sit in the water or on cradles within feet of the water 24/7 their entire lives. Ventilation is a must, not sealing.
Ventilation is definitely a must.

RV's are often a lot different than boats however as boats often live in temperature moderated environments. Water tends to keep temps close to it warmer than if one is miles from the nearest water body.

If the humidity rises in an RV then the outside temp drops severely (like below freezing, the humidity condenses on the walls and wherever it has permeated the insulation. Venting can often just provide a fresh batch of humidity.

Every situation has it's own issues with humidity.

When I run my humidifier I just place it in the shower with the door open. A short hose extends from the tank drain into the open shower drain (stopper removed). I then leave gray tank valve open and remove the garden hose adapter cover from the Valterra cap that covers the 3" drain connection. Only water running out at this point will be condensate.
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Old 01-11-2021, 01:44 PM   #14
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I have Maxx Air vent covers on my trailer. I leave the vents cracked open year round. Keeps the humidity down to whatever is ambient.
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Old 01-11-2021, 01:58 PM   #15
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[QUOTE=MendocinoExplorer;2477991]We keep our Sonoma (Evo) 220RBS travel trailer at our home, doors, vents, windows, shut.
Since we live on the ocean coast, the humidity is about 95% or more, 95% of the time.
We have a small dehumidifier inside that we empty about twice a week. About a cup of water in about a week. Other than emptying the dehumidifier, we do not open the doors, etc. We close the door quickly when entering to empty the unit.
Solid vinyl floor, laminate exterior, carefully inspected joints.


Question: Where is this water coming from?

A) From the plumbing traps in the sinks and toilet
B) From leaks in the ‘envelope’ (windows/doors/vents/etc.)
C) Sucked through the skin of the trailer
D) From the ‘weep holes’ in the windows

[Edit]:
E) Slide Out seals

Thanks all for your feedback.

[Background]: My DW is VERY sensitive to molds, vapors, etc.. When we purchase our TT new, it took 3 months of outgassing (omitting the details here) to get it to the condition that she could enter without breathing difficulties.
[/Background]



I really like the 'breathing' analogy – makes sense.

We do have a remote AcuRite sensor that monitors Temperature (F.) and Humidity:
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Tried DampRid and EvaDry (very familiar with these products), and no joy...

We do keep all the doors, drawers, etc. open, but the under-the-mattress idea is helpful. Thanks again on this one.


'WanderMore' said that mold issues can start at around 50% H..
We do have a $250 big-deal dehumidifier that can suck the paint off the walls.

Should I be using big one instead of the little one?
What is the 'ideal-yet-practical' percentage to shoot for?

Thanks again for all your feedback so far,

Rennie
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Old 01-11-2021, 02:25 PM   #16
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Rennie, I have perfect site for you that relates RH, dewpoint, and humidity. You enter 2 of the known measurements (temp and humidity in your case), and see how that affects dewpoint. Although this site is focused on preservation of materials, such as museums and libraries, it is still relevant.


Dew Point Calculator


**as you can see by clicking on solve for dew point, then moving RH slider to 50%, there is no temperature at that level which would contribute to mold growth.
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Old 01-11-2021, 04:39 PM   #17
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Quote:
Originally Posted by MendocinoExplorer View Post
We keep our Sonoma (Evo) 220RBS travel trailer at our home, doors, vents, windows, shut.
Since we live on the ocean coast, the humidity is about 95% or more, 95% of the time.
We have a small dehumidifier inside that we empty about twice a week. About a cup of water in about a week. Other than emptying the dehumidifier, we do not open the doors, etc. We close the door quickly when entering to empty the unit.
Solid vinyl floor, laminate exterior, carefully inspected joints.


Question: Where is this water coming from?

A) From the plumbing traps in the sinks and toilet
B) From leaks in the ‘envelope’ (windows/doors/vents/etc.)
C) Sucked through the skin of the trailer
D) From the ‘weep holes’ in the windows

Any other ideas?

Thanks in advance,
Rennie

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Old 01-11-2021, 06:57 PM   #18
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Thanks Kris!

Using the Dew Point Calculator involved reading the explanations (and a bit of head-scratching), but it is VERY useful in figuring out the next thing I needed to know ( the target Relative Humidity for the interior of my travel trailer ).

For some of the other Forum members that may not have the time to delve into this, below are the values that make most sense to me to share with others. The goal is to keep the humidity low enough to prevent the mold spores from 'hatching' (expressed in this chart as 'Days to Mold'). When the Relative Humidity ( RH ) increases from the left RH column to the right RH column, the calculator indicates the possibility of mold growth ( expressed in 'days' ).

Click image for larger version

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Here is a screenshot of the Dew Point Calculator interface:

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So, I think that I learned that (for me), I should use a target of 65% Relative Humidity as my 'keep-it-there-and-don't-have-to-think-about-it' target. 65% is easy enough to reach with my small dehumidifier. The temperature swings where I live allow for this percentage to be low enough that I can keep on top of any mold beginning to start in the trailer. In my case, the worst situation would be an unusually hot day (inside the trailer), and I still have almost 2 weeks to become aware of this and do something about it. Note: I do have an 'alarm'/'alert' set on my remote monitor that warns me when the relative humidity goes above 65%.
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Old 01-11-2021, 07:10 PM   #19
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Rennie, I agree there was some figuring out to do first time I used it. That's why I private messaged you my phone number to answer any questions, lol. Make sure you play around with the sliders, like what your trailer temps normally are. Then as you slide the RH slider up or down, you'll see values on the smaller 'Preservation Values' table change. At some point you will see 'Risk' pop up for mold.
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Old 01-12-2021, 04:39 AM   #20
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The humidity is in the air, evaporated off that great huge bathtub called the ocean.. The warmer the air the more distance between the gas molecules for water molecules to be held in suspension.

As the air cools the gas molecules get closer together, "squeezing" the water molecules out of solution............causing, you guessed it,,,,,,,, condensation. It may be in the air forming a cloud, it may be on the inside of your windows.

Your camper breathes constantly. As the air warms it expands and it is forced out of every minute hole, and when it cools, it shrinks and more is pulled back in from outside. You can't stop it, just live with it and your de-humidifier.
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