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Old 09-25-2022, 09:16 AM   #1
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Window Condensation

New to Airstreaming. We woke up today with condensation on most of the windows, as it was cold outside and we had the heater running overnight. We know that moisture inside our unit is not good.

What is the best practice for preventing condensation and for dealing with it once it occurs?

My first thought was to wipe it away, but we chose to first watch what happens. The condensation on the windows that open seems to drain away, but not into the interior living space. Is that water finding its way out, or is it flowing between the walls?

As far as prevention is concerned, should we be leaving a window or vent cracked open to minimize condensation?

Appreciate learned advice.

Thanks!

Josh
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Old 09-25-2022, 09:40 AM   #2
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Airstreams, like most well sealed trailers, are prone this condensation issues like this when running the heat. There are many threads on this, but I think you've already mentioned a common solution. Crack a window, or maybe two. This is what we do.
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Old 09-25-2022, 11:03 AM   #3
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Two people, a large dog, showering, and cooking add lots of water to the air in our little 19'. Even in the coldest weather (significantly below freezing) we have one window and one roof vent slightly open. With the heat running, the roof vent is like a chimney and the window is a fresh air intake and our indoor humidity is well controlled.

When showering, we keep the shower/toilet door closed. After showering, we do, of course, use the extraction fan in the enclosure.

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Old 09-25-2022, 12:06 PM   #4
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You say you had the heater running all night? Is this your furnace? Or is it a catalytic? If it is your furnace you may have a leak in the exhaust to the outside. This would dump the products of combustion inside. A classic sign is excess humidity.
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Old 09-25-2022, 12:11 PM   #5
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We leave the shower and bathroom vents open all the time when camped. Frequently we open the MaxxAir vents too, especially during the day when it warms up.. This dries things out well for us.
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Old 09-25-2022, 12:23 PM   #6
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You say you had the heater running all night? Is this your furnace? Or is it a catalytic? If it is your furnace you may have a leak in the exhaust to the outside. This would dump the products of combustion inside. A classic sign is excess humidity.
CO detector should be screaming if this is happening. Even a brand-new perfectly fine propane furnace will still result in condensation if things are closed up tight. We've even had condensation form on the windows when using an electric space heater.
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Old 09-25-2022, 12:29 PM   #7
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CO detector should be screaming if this is happening. Even a brand-new perfectly fine propane furnace will still result in condensation if things are closed up tight. We've even had condensation form on the windows when using an electric space heater.
CO is not created until the oxygen is depleted. When the discharge vent on a furnace leaks the furnace is still able to bring in outside air to the burner so you are not correct. A RV furnace is supposed to be sealed combustion. It should have zero effect on the humidity if working correctly. For all we know he was using a Mr Buddy?
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Old 09-25-2022, 12:39 PM   #8
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CO is not created until the oxygen is depleted. When the discharge vent on a furnace leaks the furnace is still able to bring in outside air to the burner so you are not correct. A RV furnace is supposed to be sealed combustion. It should have zero effect on the humidity if working correctly. For all we know he was using a Mr Buddy?
Sealed combustion in the furnace does nothing to the inside air produced from well, living inside the AS; 2 humans and a dog can do a pretty goo djob of creating moisture just from sleeping...right answer is vent and window open. Other option is dehumidifier, assuming humidity in the area you are camping; fall or winter. We use one in Texas/NC/FL anywhere that has high humidity, most all the year, when camping. If in one of the Northern states with low or no humidity, you will still get moisture unless you keep vent and window open a bit.
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Old 09-25-2022, 12:46 PM   #9
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Sealed combustion in the furnace does nothing to the inside air produced from well, living inside the AS; 2 humans and a dog can do a pretty goo djob of creating moisture just from sleeping...right answer is vent and window open. Other option is dehumidifier, assuming humidity in the area you are camping; fall or winter. We use one in Texas/NC/FL anywhere that has high humidity, most all the year, when camping. If in one of the Northern states with low or no humidity, you will still get moisture unless you keep vent and window open a bit.
What dehumidifier do you use gypsydad?
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Old 09-25-2022, 12:55 PM   #10
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CO is not created until the oxygen is depleted. When the discharge vent on a furnace leaks the furnace is still able to bring in outside air to the burner so you are not correct. A RV furnace is supposed to be sealed combustion. It should have zero effect on the humidity if working correctly. For all we know he was using a Mr Buddy?
We're talking about a 2022 trailer here. Could the furnace be defective and causing combustion gases to enter the cabin? Of course. But it is very unlikely as compared to the other issues being discussed here. An inspection of the furnace can cross this off the list of possible suspects.

The furnace doesn't need to add any moisture in the air to have condensation on the windows. Just having warm air inside and cold air outside is going to cause it, just like when it forms on a glass of ice water on a hot day. Like I said earlier, this has happened to us using an electric space heater.

The only solution is to lower the humidity level inside the trailer, either through letting in outside air or using a dehumidifier are the most common.

This is discussed on pages 3-8 and 3-9 of the Flying Cloud owners manual.
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Old 09-25-2022, 12:56 PM   #11
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Originally Posted by gypsydad View Post
Sealed combustion in the furnace does nothing to the inside air produced from well, living inside the AS; 2 humans and a dog can do a pretty goo djob of creating moisture just from sleeping...right answer is vent and window open. Other option is dehumidifier, assuming humidity in the area you are camping; fall or winter. We use one in Texas/NC/FL anywhere that has high humidity, most all the year, when camping. If in one of the Northern states with low or no humidity, you will still get moisture unless you keep vent and window open a bit.
You are right assuming it IS sealed. Of course other things also create humidity but as a licensed HVAC contractor the number one thing we look for during the heating season is excess humidity indoors. This is the number one indicator of a venting issue. This is a safety issue on a new trailer so it should at least be checked. Tell the dealer you have excess humidity inside when the furnace operates and see what their reaction is. This should be at least looked at first especially since this is a new Airstream!
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Old 09-25-2022, 01:17 PM   #12
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There is only one cause…too little ventilation. The moisture inside is too high for the temperature outside. I see this in houses all the time as a real estate appraiser. Typically worse in homes with passive heat like hot water or electric.

1. Turn on the vent fans.
2. Run a dehumidifier. You can get small ones for campers.
3. The forced air furnace will take more out. Running your heat pumps will not work.

Also make sure and run the stove fan Whenever cooking. Even if it isn’t that hot. Lots of moisture while cooking. And run both fans in the shower and over the sink at the same time when using bathroom.
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Old 09-25-2022, 01:24 PM   #13
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There is only one cause…too little ventilation. The moisture inside is too high for the temperature outside. I see this in houses all the time as a real estate appraiser. Typically worse in homes with passive heat like hot water or electric.

1. Turn on the vent fans.
2. Run a dehumidifier. You can get small ones for campers.
3. The forced air furnace will take more out. Running your heat pumps will not work.

Also make sure and run the stove fan Whenever cooking. Even if it isn’t that hot. Lots of moisture while cooking. And run both fans in the shower and over the sink at the same time when using bathroom.
Come on man! The first thing you should be looking at is the appliance vents. Dont just blow them off. That is the number one source of humidity. I have even stopped at houses I see with heavy condensation inside to warn them.
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Old 09-25-2022, 01:53 PM   #14
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Originally Posted by Daquenzer View Post
There is only one cause…too little ventilation. The moisture inside is too high for the temperature outside. I see this in houses all the time as a real estate appraiser. Typically worse in homes with passive heat like hot water or electric.

1. Turn on the vent fans.
2. Run a dehumidifier. You can get small ones for campers.
3. The forced air furnace will take more out. Running your heat pumps will not work.

Also make sure and run the stove fan Whenever cooking. Even if it isn’t that hot. Lots of moisture while cooking. And run both fans in the shower and over the sink at the same time when using bathroom.
A direct vent furnace like we have in our trailers do not add or remove any moisture from the inside air. The Dew point of the air does not change when heated. The Dew point is what determines the temperature that moisture will condense out of the air. If you all are seeing condensation while running your furnace then you have a leak of flue gas. The way the OP describes it the water was running down the glass into the skin. This is not the dog. The furnace needs to be checked immediately and not by Billy Bob's mobile RV repair.
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Old 09-25-2022, 02:05 PM   #15
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To: MMFJC

Open your vents and windows if you can.
Minimize stove top use, boiling water, etc.
Minimize hot showers

And, when that all fails to truly correct the issue, buy a dehumidifier.

We run one like this. Sure, it's a bigger one. We tried a small table top one. Then realized we needed, and wanted things, including the windows, to be DRY.

This bad boy sits real nice right at the end of our dinette. AND, simply put, it works.

https://www.homedepot.com/p/GE-22-pt...22LA/315445853
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Old 09-25-2022, 02:13 PM   #16
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A direct vent furnace like we have in our trailers do not add or remove any moisture from the inside air. The Dew point of the air does not change when heated. The Dew point is what determines the temperature that moisture will condense out of the air. If you all are seeing condensation while running your furnace then you have a leak of flue gas. The way the OP describes it the water was running down the glass into the skin. This is not the dog. The furnace needs to be checked immediately and not by Billy Bob's mobile RV repair.
I think that it's been acknowledged that there is a possibility of a furnace issue. Checking for a furnace problem is always a good idea if someone is unsure of the cause or suspects it's not running properly. But it's just not accurate to make a blanket statement that "If you all are seeing condensation while running your furnace then you have a leak of flue gas."

We've had many people talk about having the exact same event take place in their trailers. I even mentioned that I've had this happen when using an electric space heater, when there is absolutely no chance that it was combustion gas related.

Yes, water can run down the glass and pool up enough to run down the interior walls. Yes, this can happen when using just an electric space heater. The brown stains on my interior walls when I bought the trailer will testify to that. The furnace has been inspected, is working fine, and has no leaks.

The weather right now around here is a perfect setup for this type of thing to occur - warm & relatively humid days followed by nights in the upper 30s to the low 40s. Windows are closed up before bed and the heat is put on low. All the moisture that was inside the trailer from the afternoon is still in there. Add some chilling on the outside of the glass and now you have condensation on the inside of the glass windows. Now add the moisture from a shower or two, and possibly also coffee & breakfast being cooked, and the moisture is now rolling down the glass.

Again, see pages 3-8 and 3-9 in the Airstream Flying Cloud manual. It describes exactly what the OP and others have experienced.
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Old 09-25-2022, 02:21 PM   #17
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Thank you all for the replies. I remember reading about venting but couldn’t remember where. Opening windows and vents seems contrary to heating your RV, but I certainly understand why venting is necessary in these circumstances!
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Old 09-25-2022, 02:24 PM   #18
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I think that it's been acknowledged that there is a possibility of a furnace issue. Checking for a furnace problem is always a good idea if someone is unsure of the cause or suspects it's not running properly. But it's just not accurate to make a blanket statement that "If you all are seeing condensation while running your furnace then you have a leak of flue gas."

We've had many people talk about having the exact same event take place in their trailers. I even mentioned that I've had this happen when using an electric space heater, when there is absolutely no chance that it was combustion gas related.

Yes, water can run down the glass and pool up enough to run down the interior walls. Yes, this can happen when using just an electric space heater. The brown stains on my interior walls when I bought the trailer will testify to that. The furnace has been inspected, is working fine, and has no leaks.

The weather right now around here is a perfect setup for this type of thing to occur - warm & relatively humid days followed by nights in the upper 30s to the low 40s. Windows are closed up before bed and the heat is put on low. All the moisture that was inside the trailer from the afternoon is still in there. Add some chilling on the outside of the glass and now you have condensation on the inside of the glass windows. Now add the moisture from a shower or two, and possibly also coffee & breakfast being cooked, and the moisture is now rolling down the glass.

Again, see pages 3-8 and 3-9 in the Airstream Flying Cloud manual. It describes exactly what the OP and others have experienced.
I don't need to read pages 3-8 and 3-9 in the manual. Too many people are saying things that are not correct. This is a safety item. The trailer is under warranty. I'm saying take it in and get the furnace inspected. Don't just crack the vents. And a Direct vent furnace does not add moisture to the inside air. Ever! Unless there is a leak.
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Old 09-25-2022, 03:41 PM   #19
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Thank you all for the replies. I remember reading about venting but couldn’t remember where. Opening windows and vents seems contrary to heating your RV, but I certainly understand why venting is necessary in these circumstances!
On trailers I build I include a small Heat Recovery Ventilator that operates on 12 volts. This helps control the humidity.
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Old 09-25-2022, 03:45 PM   #20
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I don't need to read pages 3-8 and 3-9 in the manual. Too many people are saying things that are not correct. This is a safety item. The trailer is under warranty. I'm saying take it in and get the furnace inspected. Don't just crack the vents. And a Direct vent furnace does not add moisture to the inside air. Ever! Unless there is a leak.
I'm not saying that the furnace is adding moisture. The moisture is already there. The furnace (whether it's propane or electric) is adding heat. Heat on one side of a piece of glass with cold on the other side makes condensation.

This has been a problem for as long as people have been camping in travel trailers. My first time out in a trailer was on a hunting trip with an Army recruiter in a vintage canned ham trailer. There was no heat in the trailer at all, but when we woke up in the morning there was condensation everywhere.

It's even possible for this to happen when camping in a tent. Two people sleeping in a moderate sized tent on a cool/cold night is enough to make it rain inside the tent in the right weather. Condensation happens.

If there is reason to question a furnace then of course it should be inspected, but there is no need to create panic where it's not needed. This is a known issue, and if you do a search on Air Forums you'll see dozens of threads on the topic.
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