How to Stop Condensation From Fogging Up RV Windows

Anyone that has gone RVing or camping in a trailer in the cooler months knows that condensation can be a huge problem. If you’ve got it really bad, you’ll see water dripping off your windows and walls. Unfortunately, condensation like that can damage your RV–and it can encourage mold to grow, which can be a health concern.

water dew on glass

It is surprisingly easy to reduce, or even stop, condensation from forming in your RV. Turning on your RV’s defrosters, turning on a dehumidifier, or even using moisture absorbers are all great options for RVers.

Of course, there are pros and cons to each of the above methods. For instance, you might have to turn on your RV to turn on your defroster. You’ll need electricity to run a dehumidifier. Moisture absorbers will need replaced, and that can be a cost that really stacks up!

Personally, I find that dehumidifiers are the all-around best option for RVs (and even cars, as I’ve used them in cars before as well).

Read on to see why I’ve come to that conclusion and to see why the other options aren’t nearly as good.

Additionally, I will go over other ways you can reduce humidity in your RV, share some helpful tips on humidity levels, and a whole lot more. So, without further ado, strap on in and come along for the ride!

Why Are Dehumidifiers the Best Option for Getting Rid of Condensation in RVs?

I know that most people who have blogs don’t like jumping straight to the essence of their pieces, but I’m here to help As such, I’m giving you guys the best answer to your condensation problem right now.

And, as you know, that answer is a dehumidifier.

Dehumidifier on a window sill overlooking a forest

No, a dehumidifier isn’t going to be your end-all solution, but it will really help in the long run and it will do a ton of the heavy lifting for you. And it will do all of that work with a very small cost to you, when compared to the other two options you have.

A dehumidifier like the one I have a picture of here (the Seavon one) is more than ample for an RV. I just got turned onto this particular brand this past year and have thoroughly enjoyed it.

You can buy this Seavon dehumidifier on Amazon here. You can get a cheaper one from Amazon here, but it’s a smaller model. Or, if those doesn’t interest you, you can check out the rest of my site for the other great dehumidifiers I’ve checked out. (But trust me, this Seavon one will be your best call for an RV!)

Alright, now that you know which dehumidifier I recommend, odds are you’re wondering why I chose this particular one and (if you’re like me), you’re probably still wondering why and how a dehumidifier is what you need and will help you.

So, let’s dive into things!

How Does a Dehumidifier Reduce Condensation?

Dehumidifiers are machines that are used to reduce the amount of humidity in the air. Higher levels of humidity paired with low outside temperatures cause condensation to form on the windows and walls of RVs and trailers.

So, if you simply reduce the amount of humidity, you reduce the level of condensation that can form.

It really is that simple.

Now, there are lots of less simple things that you might want to consider, but most people will be able to get along fine with just knowing that high humidity levels are their RVing dream’s enemy. It’s all that humidity that can cause rot, mold, and warp the wood in your RV. Killing that humidity can save you the headache.

Now, if you’re interested in the science of how dehumidifiers reduce humidity then you’re out of luck. There isn’t enough time today for me to fully explain that. But I can try and summarize things. In short, dehumidifiers use electricity to power a system (there are several systems and methods) which will be able to cause the humidity in the air to precipitate out of the air and fall into a collection basin for all the water your dehumidifier pulls out of the air.

Now, for my astute readers, you probably are thinking about something important about humidity right now. That’s the fact that there is usually more humidity out there when it’s warmer than when it’s cold.

And yes, that is true.

The only reason why you’re more apt to have a condensation (and humidity) problem in the winter is because it is only during the cooler months that the temperature difference between the outside and inside is great enough to cause condensation to form.

That’s a big old rabbit trail for later on in this article, so I’ll just finish here and say that it could be wise to have and use your dehumidifier during the rest of the year as well–not just during the winters.

(Also, pro tip here, run your dehumidifier during your rainy season. I’m from Oregon, so the whole year is basically a rainy season, but most people will have a few months that see more rain than others. That rain generally causes humidity levels to rise, and that can harm your RV–whether you’re in it or not. A dehumidifier can save you the headache of walking into your RV to see a bunch of rot, mold, or other moisture issues after a long time in storage!)

Why is a Dehumidifier the Best Choice for RVs?

white and blue bus on road during daytime

From a cost perspective, dehumidifiers will be your best choice in the long run for reducing the amount of condensation and humidity in your RV. There are several reasons why that’s the case and I’ll explain that as we read on.

Right off the bat, let’s compare the cost of a dehumidifier to the cost of running your RV all night on defrost or you buying a bunch of moisture absorbers for the rest of eternity.

Cost of Running Your RV All Day:

Assuming your engine burns about a half gallon of gas an hour as it idles (your engine will have to idle as you have your defrosters on), that equates to 12 gallons of gas burned a day. (AAA says that it takes between a quarter to a half-gallon an hour, depending on the engine. Since RV engines are larger than normal car engines, we’ll conservatively go for the half-gallon burn rate.)

According to AAA, current gas prices are $3.53 a gallon. At that cost, you’ll end up burning through $42.36 a day just to keep the condensation and humidity at bay.

If you want to run the numbers yourself on the cost to idle, here’s an easy equation you can plug into a calculator:

(Cost of Fuel) x (Number of Hours Idling) x (How Much Fuel Your RV Burns in Idle) = (Cost to Run)

If you think about how much that adds up to after a whole week of RVing, then you might get worried. (Here’s a hint, it’d cost just shy of $300 at current gas prices.)

Now, if we compare that to the cost to purchase a dehumidifier, which is around 40 dollars, then you see why that option is superior.

Hold up, stop what you’re thinking! I know someone out there is like, “Well, won’t I end up burning gas to run the dehumidifier?”

Well, you’re right. You might have to burn some gas to run a dehumidifier. However, if you have a battery, a generator, or a campsite that provides electricity, then you’re golden! Your dehumidifier will be a lot more energy efficient than your RV’s defroster.

Cost of Moisture Absorbers for Your RV

RV moisture absorbers can be pretty affordable and can definitely be a good choice for RVers, but their cost does add up after a few years. For my family, when we use these, we have to replace them every one to three months, depending on the weather.

When you’re buying RV moisture absorbers in bulk, you can get a pretty good price on them too. For six, it’s about 20 bucks. (Here’s a link to the ones that my family uses on Amazon.)

Running off the numbers I already mentioned, those six will last my family a year or so. Odds are it would do the same for most RVers too.

But there’s an issue there, after two or so years, you’ve spent more money replacing moisture absorbers than it would have cost to buy the dehumidifier I recommended. Extrapolate that out a few more years and you’ll end up spending hundreds of dollars.

And that’s why I recommend a dehumidifier over a moisture absorber.

But I will admit that there is a place for moisture absorbers. That’s why my family uses them! They are the perfect fit for any application that you don’t have access to any power. Depending on your circumstances, that might be you! So, I won’t say that moisture absorbers should be avoided. They are really neat and helpful!

Other Ways to Reduce Humidity and Condensation in Your RV

Alright, so let’s say you bought a dehumidifier. Now what? Can you just do whatever? Can you dump a thousand gallons of water in your RV and not have any problems?

Well, I hate to break it to you, but a dehumidifier can’t do everything. There will still be things that you’ll want to do to reduce the chances of your RV rotting away or becoming a mold farm. While the dehumidifier will be able to cut down on how much humidity there is in your RV and cut down how much condensation you get, it isn’t the end of your journey.

In fact, there are two courses of action for RVers that will help them reduce the level of humidity in their RV.

  1. (Prevention) They can reduce how much moisture is introduced to their RV.
  2. (Mitigation) They can reduce the amount of humidity that’s already in their RV.

Of course, you’ll probably be better off doing things from both action plans, but, again, just getting a dehumidifier will be a HUGE step in the right direction.

To save us all time, I’m just going to make a table with a lot of different things that RVers can do to cut down on the humidity levels in their camper. One side will before prevention (keeping the moisture out of the RV in the first place), and the other for mitigation (cutting down how much humidity is already in the RV).

Keep Moisture Out of Your RV or Trailer
Deal With the Moisture That’s Already in Your RV or Trailer
-Park your RV or trailer in a covered area. (Rain can seep in and you won’t notice how wet things are until too late!
-Remove wet clothing prior to entering the RV.
-Use camp showers instead of your RV’s shower.
-Don’t wear your wet shoes inside your RV.
-Cook outside. Cooking can release a lot of humidity!
-Get a dehumidifier or moisture absorber. (As we’ve already gone over.)
-Open some windows or vents when it’s dry out. Winter air is usually not humid, so you can use it to dry out the air in your RV.
-Run your RV’s defrosters.
-Open up for cupboards and cabinets when your RV is stored/parked to let them air out and get rid of any residual moisture/humidity.
Table explaining several methods to reduce the amount of humidity in your RV.

Now, there are sure to be a million other things that you can do to limit how much humidity your RV has, but that table is a good start. You don’t have to do everything on the list, but doing as many as you can will go a long way.

Of course, do what works best for you. While I personally recommend air dehumidifiers and moisture absorbers, they aren’t required! They’re just really helpful tools that can help you fend off humidity and condensation.

How Do I Know if My RV Has Too Much Humidity?

I’m tossing this section in just because I know some people will be wondering it. Before you read into this section too much, just know that if you have a lot of condensation in your RV, then you have too much humidity. That’s a great indicator. However, there are more technical ways to be more sure, so that’s what I’ll get into with this section.

Another indicator that your RV has too much humidity is if you can smell mustiness, mold, or mildew. If you can see some mold taking over or see/feel any rot, then that’s yet another indicator. If things have gotten that far (so that you have mold or rot), then there is a big problem that will cost a lot of money though.

So, is there a way you can tell if you have too much humidity before then?


That comes in the form of a humidity sensor.

Humidity sensors are sure to break the bank–they can cost a whole 5 dollars! (I’m kidding about that breaking the bank. But I am quite serious about them being around five bucks!)

The little sensor that I’m holding in the picture to the right cost me $4.90 when I picked it up. You can check out its current price and pick it up at Amazon here, if you’d like it.

Not going to lie, I’ve had a little too much fun with it, which makes me quite nerdy, I know. Hahaha However, let me remind you that I’m the one with an air purifier blog, so I have to be a nerd for this stuff!

What is a Good Humidity Level?

Once you buy a humidity sensor, you will have to let it run for a few minutes. I find that it usually takes around five minutes for the sensor to give out a good reading of the room it is in.

But what number should we be looking for?

So, if you buy the super cheap humidity sensor I recommend and have, then you’re going to be looking at the number on the left, which is a percentage. That number, according to the EPA, should be between 30 and 50 percent. If that number is above 60%, then you have a problem. (And you’ll need a dehumidifier in order to ensure you can get that number down consistently.)

The humidity level in your RV or trailer will constantly fluctuate. Even the air in my house goes up and down 20-some percent in a week! As such, you will need to keep the sensor on hand and either write down the readings, or just keep a mental note on things. If the levels are consistently high, then you will need to take action to remove some humidity. Otherwise, rot, mold, and condensation will always be a problem.

Another thing of note is that humidity levels will usually be higher in the spring, summer, and fall. I know that sounds weird, since you’re just now seeing the condensation now in the winter months (probably), but it’s true.

The reason why that is the case is because warmer air carries more moisture with it.

And, if you think about it, you living in your RV during the winter will mean that it’ll be pretty warm. You’ll be cooking in, living in, and heating your RV, which means it’s the perfect place for humidity levels to rise. The only reason why the condensation shows up in winter is because of the large temperature difference between the air in your RV and the cold outside.

When Should I Run a Dehumidifier in My RV?

Depending on where you live, you might want to run your dehumidifier all year.

I know that sounds like a lot, but, as I already mentioned, humidity levels are higher in the spring to fall times and, if you’re camping during the winter months, then that will keep humidity levels higher in your RV then too.

While the cost of electricity to run a dehumidifier will be easy to overlook, there is one big thing that you will have to keep in mind–emptying the dehumidifier.

All the water your dehumidifier pulls out of the air has to go somewhere, for most air purifiers out there that you might want in an RV, that will be a storage tank. For the dehumidifier I recommended, I have to empty it once a week when things are really humid, sometimes more.

However, if your RV is just sitting outside and it isn’t too wet, then odds are you won’t have to worry too much about the dehumidifier. Maybe check on it every other week or something. It really varies depending on where you live, so you’ll have to figure out what works best for you.

Also, a lot of dehumidifiers (including the one I recommend) automatically shut off when their tanks are full. That way you don’t have to worry about a spill! If you decide to shop around, be sure to find a dehumidifier with that capability.

Frequently Asked Questions:

What is Condensation?

Condensation is the accumulation of water that comes from the atmosphere and collects on cool surfaces, such as mirrors, windows, and glasses of cold drinks. It can be a good indicator of a high humidity issue in your home or RV.

What Do I Need to Look for in a Dehumidifier for My RV?

Look for a dehumidifier that has an automatic shut-off when it is full, you don’t want any spills. Also find one that is made for an RV of your size. Most RVs are between 250 and 350 square feet, so find a dehumidifier made for around that much area.

Thanks for reading up on why I think dehumidifiers are your best bet for limiting the humidity and condensation in your RV! I hope I was able to help you all out and maybe make your next RV trip a lot better! (And drier.)

If you’d like to continue reading what I’ve got, check out some of the articles below, which I think might interest some of you!

How Do I Know if I Need a Dehumidifier or a Humidifier? | What’s the Right Humidity for My Home?

What’s the Best Air Purifier for Someone with Pets?

My Dehumidifier Freezing Experience | Can A Dehumidifier Freeze During the Winter? Yes. Does a Dehumidifier Break if it Freezes? Maybe.

Do I Need an Air Purifier in My Bathroom? | 6 Reasons Why You Should Get an Air Purifier for Your Bathroom

Jonathon Silva

Jonathan Silva is our longtime Air Purifier Essentials author. He has been writing on air purification technologies for his entire professional career.

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