Tuesday, March 21, 2023


How do I reduce condensation on RV’s windows in cold weather?

Hey, Dave,
When camping in cold weather and heating with the unit’s propane heater, a lot of condensation collects on all the windows. Is there a dehumidifier that runs off its own battery power or that can be connected to the unit’s 12v system to effectively remove/reduce the excess moisture? —Tim, 2021 r-pod 192

Hi, Tim,
In an RV with a typical propane heater, liquid propane (LP) is combined with air/oxygen and as it is burned, creates moisture in the air. When this moisture contacts a cold surface, it creates condensation. This shows up on and around windows and inside cabinets and closest as there is very little air circulation in these closed spaces and it gets colder than the rest of the unit.

Get better airflow

The first thing I would recommend is to open a few of the overhead cabinet doors and closets and place a few fans around the inside to get better airflow. Periodically open a roof vent slightly to pull out some of the warm, moist air that rises to the ceiling. If you do not have dual pane windows, it would be good to install a plastic barrier or shrink wrap.

There are several dehumidifiers on the market ;however, I have not tried any of the wireless models as of yet. I have tried DampRid, which works fairly well when placed in strategic places. Recently I came across a product called H2Out. I got samples from the company which I have placed in a Class A storage unit to test. After one month of testing I have found no condensation and the units are still working as designed. It uses silica beads that absorb the moisture and turn color when saturated. Then you place them in an oven for an hour to dry the beads out and you can reuse them. The RV Doctor, Gary Bunzer, did a test and was very impressed a few years ago. We will see how my tests come out.

Portable catalytic heater

Something that I have used in the past is supplementing the heat with a portable catalytic heater such as the Olympian or Mr. Heater. It uses a smaller propane bottle and has much lower condensation than the forced air standard furnace. You can turn the onboard furnace down and place the portable unit in the bedroom at night or living room during the day rather than heating the entire unit. It’s very safe and produces almost no carbon dioxide.

 You might also enjoy this from Dave 

Can I use a calcium chloride product to reduce moisture in RV?

Dear Dave,
Is a calcium chloride product like Dri-Z-Air adequate to dehumidify our RV? Or should we use a plug-in dehumidifier? —Bruce, 2017 Sunseeker

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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G Smith
1 month ago

By not specifically separating propane furnaces from catalytic propane space heaters when talking about adding moisture to the air, you are perpetuating the myth that furnaces exhaust water to the inside of the coach.

Your further assertion that catalytic heaters add little carbon dioxide to the air will definitely cause confusion amongst those that are learning about the subject. Carbon MONOXIDE (CO) is the relevant threat, not CO2.

Steve Hericks
1 month ago
Reply to  G Smith


Furnaces use external combustion air and discharge NO COMBUSTION PRODUCTS into the cabin.

‘Buddy’ heaters and any portable propane heater, on the other hand, discharge a good amount of BOTH water and carbon dioxide (both normal, harmless combustion products) directly into the cabin. Carbon MONOXIDE is an ABNORMAL combustion product arising from incomplete combustion as a result of improperly operating equipment or oxygen starvation.

Propane produces 26oz of water per 16oz of propane combusted. Portable heaters are BAD NEWS if condensation is a problem. Even with a window partially open, the majority of the water vapor released will stay in the cabin.

Bill Semion
1 month ago

The other trick to avoid condensation is to stop breathing. When you exhale, you breathe out moisture. It is inevitable.

Last edited 1 month ago by Bill Semion
Scott R. Ellis
1 month ago

Wow, is this disturbingly wrong.

Your “conventional propane furnace” does, indeed, produce H2O as a combustion byproduct . . . and then it vents that vapor outside with the rest of the combustion gases. The only propane heat that actually increases indoor humidity is a “Little Buddy” type or (though not quite as much) the catalytic heater in the article.

The solution to condensation is venting. Slightly open the physically lowest window you have and crack a roof vent: problem solved.

1 month ago
Reply to  Scott R. Ellis

Correct. In fact this shows up later in this newsletter.

1 month ago
Reply to  Scott R. Ellis

Another major factor is seeking out an RV with dual pane windows. I have found condensation issues to be considerably less to nonexistent (depending on how cold) with dual panes.

1 month ago
Reply to  Scott R. Ellis

Correct, this article is flat out wrong.

Dan M
1 month ago
Reply to  TIM

Agreed. A properly working furnace (aka the heat exchanger isn’t cracked) won’t add any humidity to the air as all the exhaust is vented outside. It’ll actually reduce the relative humidity by raising the temperature of the air.

If an RV furnace is adding humidity then it’s also letting exhaust gasses into the space which is very dangerous and it should be inspected by a qualified repair person ASAP.

Those catalytic heaters, like. Mr Buddy, do add humidity to the air, but in a pinch they’re better than not having heat.

I can’t speak to using any sort of battery powered or 12v dehumidifier but since a compressor style dehumidifier is basically just an AC that vents the heat back into the room you can expect them to be pretty power hungry. Putting plastic over my windows (unfortunately single pane) both stopped them condensing humidity and keeps the rig much warmer, though I do still get condensation on the metal frames. My solution has just been to run a dehumidifier constantly when it’s cold enough out to form condensation and pull the humidity down to about 25% to minimize it.

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