Just looking for opinions.We are staying in a very cold area (mid-teens at night) so we run heat quite a bit. We have a Class A with the large front windshield and we keep the curtains drawn almost all of the time. The windshield, not getting much heat from within, will actually show condensate and even ice on the inside. This will eventually melt and drip onto the dash.My question(s) runs to whether or not it makes sense to open the curtains and let the heat get to the windshield - or not? The curtain seems to do a good job of keeping the cold out so I am not sure which way is more efficient, or more used by others.Another question has to do with a dark screen cover that snaps over the windshield on the outside (normally used in sunny conditions) and whether or not it would have any thermal value in the scenario noted above (very cold temps)?Thoughts?

Ultimately you need heat and airflow on the window. We placed an electric heater in the front of our rig. The other thing we did was run a mechanical dehumidifier on the maximum fan setting and at the lowest humidity level possible. This keeps the baseline humidity in the coach is lower. All of these combined reduces the amount of condensation on the windows. Finally a fan blowing on the windshield will also help in extreme situations.

I would probably just put a rolled-up towel in the corner junction between the windshield and the dashboard to sop up whatever condensation/frost drips down.The cover on the outside would probably help some, though not entirely cure the problem. If it were insulated it would help more, perhaps by interposing a blanket or something between the cover and the windshield if that is practical. The basic cause of the condensation, of course, is that the temperature of the inside surface of the glass is colder than the dew point of the air in the cabin (and, if it's frosting rather than dripping, also below freezing). Dehumidifying the air will lower the dew point, but going too far in that direction makes for uncomfortably dry air for you to live in.

I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.

way2roll wrote:I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air. You can tell this by looking at the outside vent for the furnace it is a dual tube vent combustion air is drawn in on the outside of the vent and the exhaust gases are vented on the inside tube. This has the benefit of keeping the outside of the vent cooler than it would be.

msturtz wrote:way2roll wrote:I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air.A lot of folks disagree;http://www.irv2.com/forums/f93/engineering-help-water-from-propane-104216.html

Condensation/Temp Control | Good Sam Community

way2roll
Navigator II
Nov 14, 2018
msturtz wrote:
way2roll wrote:
msturtz wrote:
way2roll wrote:
I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.

You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air.

A lot of folks disagree;

http://www.irv2.com/forums/f93/engineering-help-water-from-propane-104216.html

The confusion is coming from the use of ventless heaters. Installed propane heaters are prohibited from venting exhaust gas (including water vapor) inside the coach.

I am not going to get into a pi$$ing match with you over it. If you tell me that RV furnaces are designed to mitigate water vapor induction into the coach when it's well known that burning lp generates 1-2 gals of water per gal of LP - sorry but that's a hard sell. I tend to believe that your LP furnace - vented or not - pumps a good amount of water vapor into the RV. It's certainly not going through any sophisticated air scrubber as you can smell the additives in the LP when it burns. And if you can smell that, it's a good bet you are getting exhaust gasses - not just the heat. LP furnaces are not complicated and the vents are passive. Moving on.
rgatijnet1
Explorer III
Nov 14, 2018
I used a 120 volt fan to blow air across the windshield as well as circulate the heat. This worked fine for us since we traveled mostly in Winter and in the mountains. We had several nights with below zero temps and the fan kept our widshield clear.
msturtz
Explorer
Nov 14, 2018
way2roll wrote:
msturtz wrote:
way2roll wrote:
I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.

You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air.

A lot of folks disagree;

http://www.irv2.com/forums/f93/engineering-help-water-from-propane-104216.html

The confusion is coming from the use of ventless heaters. Installed propane heaters are prohibited from venting exhaust gas (including water vapor) inside the coach.
way2roll
Navigator II
Nov 14, 2018
msturtz wrote:
way2roll wrote:
I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.

You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air.

A lot of folks disagree;

http://www.irv2.com/forums/f93/engineering-help-water-from-propane-104216.html
msturtz
Explorer
Nov 14, 2018
way2roll wrote:
I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.

You are technically correct burning propane does create a lot of water vapor, however per code RV furnaces must have an external air intake and external exhaust for combustion. All you get inside the coach is hot dry air. This is not true with small portable heaters. So no running your RV furnace will not put water vapor into the air. You can tell this by looking at the outside vent for the furnace it is a dual tube vent combustion air is drawn in on the outside of the vent and the exhaust gases are vented on the inside tube. This has the benefit of keeping the outside of the vent cooler than it would be.
way2roll
Navigator II
Nov 14, 2018
I had a similar issue once in our first class A. A literal waterfall was running down my windshield. A by-product of burning LP is water. So if you have an LP furnace you are not only creating condensation by differing temperatures, you are pumping H20 into the air via your furnace. Showers and cooking exacerbate the issue. The best way I have found to combat this is to open your roof vents and run the vent fans. I know it seems like you will be pulling your heated air out of the coach - and you are - but you will also be pulling out the moisture. A dehumidifier is always helpful as well.
DrewE
Explorer II
Nov 14, 2018
I would probably just put a rolled-up towel in the corner junction between the windshield and the dashboard to sop up whatever condensation/frost drips down.

The cover on the outside would probably help some, though not entirely cure the problem. If it were insulated it would help more, perhaps by interposing a blanket or something between the cover and the windshield if that is practical. The basic cause of the condensation, of course, is that the temperature of the inside surface of the glass is colder than the dew point of the air in the cabin (and, if it's frosting rather than dripping, also below freezing). Dehumidifying the air will lower the dew point, but going too far in that direction makes for uncomfortably dry air for you to live in.
msturtz
Explorer
Nov 14, 2018
Ultimately you need heat and airflow on the window. We placed an electric heater in the front of our rig. The other thing we did was run a mechanical dehumidifier on the maximum fan setting and at the lowest humidity level possible. This keeps the baseline humidity in the coach is lower. All of these combined reduces the amount of condensation on the windows. Finally a fan blowing on the windshield will also help in extreme situations.

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