Friday, February 3, 2023


RV Fact or Fiction? A propane furnace emits lots of moisture

RV blogs, social media groups and YouTube videos have exploded over the past couple of years. Some provide great information, others questionable information and some downright bad information. Can you tell the difference? In this regular column, we will post a question based on information we find online. You can then test your RV prowess by seeing how your answer compares with our experts.

Today’s Question:

Fact or fiction? To keep RV windows from sweating, use an electric space heater instead of the RV propane furnace as propane heaters emit lots of moisture.
*Paraphrased/condensed from this source.

Click here to view the answer.



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1 month ago

Actually, what happens is the scientific FACT that WARM AIR HOLDS MORE moisture than COOL/COLD air, so the warm air pulls moisture out of upholstery and wood, and your breathing, and leaves it in the air, then the warm air hits the cold GLASS windows, and plastic VENT LIDS, and condenses, making them SWEAT. Really has NOTHING to do with propane, except the HEAT it produces. Hope this Helps?

1 month ago

A byproduct of combustion is water vapor. Fortunately with the typical forced air furnace that water and other combustion byproducts are vented outside in the exhaust.

Steve Willey
1 month ago

Of course propane can emit moisture, the flat indoor units sure do. But a standard rV furnace vented to outside should not out moisture inside at al. We have a 27 foot with standard furnace and use it only winters. Never had any moisture, odor, or mold anywhere.

1 month ago

This is a myth caused by confusing your LP furnace with a Buddy heater. Any combustion will produce moisture but your furnace exhausts outside or kills you with CO. Buddy DOES steam your space. The moisture you see is from your LP stove and shower, and about a pint is your own breathing.

1 month ago
Reply to  Wolfe


Neal Davis
1 month ago

I naively voted “Fact.” Both the RVs we have had (one past and one present) are all-electric. Our sticks-and-bricks has a propane fireplace. Never have noticed a moisture problem with it, but the house is 2900 square feet and pretty open. So, voted without researching the candidates.

Glenn Struck
1 month ago

I responded “TRUE”, although your answer that it does not add moisture to the interior or the RV, it does create a lot of moisture in the combustion of the propane.
I realize that the moisture is sent outside.

Bill Semion
1 month ago

We use a thermostat controlled electric space heater all the time. we get moisture. Where’s it coming from? No one as far as i can see has answered. The answer is, YOU. You exhale moisture at night. As much as a half-pint per person, I’m told. So, there’s your moisture problem. It’s YOU! Stop breathing, and you’ll be all set! 😉

1 month ago

All furnaces that burn fuel have a heat exchanger. All flame, fuel, product of operation (smoke, CO, gas, unburned fuel byproduct etc) goes through the burner and out the exhaust. The type of fuel cannot affect the total moisture in the space or condensation in anyway. The heat exchanger passes the heat from the flame box to the plenum side through solid metal. The air inside the RV enters the air side/plenum of the furnace through the air intake and back to the cabin through the ducting. It is a sealed system. Only heat transfers, not moisture.

Condensation occurs more in an RV because the the heat from the furnace can quickly evaporate all the moisture from such a small space but the poor insulation of the glass cools the air down just as quickly and the moisture condensates as a result.

Smaller heaters don’t cause as much condensation because they just don’t heat the air or circulate it fast enough for you to see it occur.

Last edited 1 month ago by TIM MCRAE
1 month ago
Reply to  TIM MCRAE

Small buddy type propane heaters or even propane or camp stoves are a different story because they do burn a flame in your living space.

Whether they add moisture to your space is far less important than Fire or CO safety!

In my opinion you should never use any kind of open flame heat in a RV and ALWAYS have a good quality CO detector!

I have tested MANY types of CO detectors and I have found if they cost less than $20 they just don’t work! Don’t go cheap on your CO detector!

1 month ago
Reply to  TIM MCRAE

I agree with the fact the small open flame heaters are dangerous and do produce moisture. So do the catalytic propane heaters. Any heater that burns fuel will produce moisture. The catalytic heater does not have an open flame, but it is still a combustion process which produces moisture. Since they radiate heat, there is a larger safety area required in front of the heater. A catalytic heater radiantly heats objects, which in turn heats the area.
One way to reduce the moisture produced when using any type fuel supplied heater is to open a roof vent slightly. Some of the moisture suspended in the air will follow the warm heated air and vent it to the outside. Sounds counterproductive, but it will eliminate some of the moisture.

Jesse Crouse
1 month ago
Reply to  TIM MCRAE

The general public needs to understand-“You get what you pay for it”. And buy the applicable device for the use.

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