Moisture buildup on windshield using furnaces

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Moisture buildup on windshield using furnaces

November 24, 2013, 08:44:09 am

When I turn on my furnaces for heating I get a lot of moisture buildup on the windshield. Should I be opening a vent or running another fan or something to eliminate this problem.

Re: Moisture buildup on windshield using furnaces

Reply #1 – November 24, 2013, 09:00:47 am

Dan,

The furnace itself will not add moisture, unless the heat exchanger has failed. And if that happened, moisture would be the least of your issues-- you would have combustion gasses entering the coach.

The issue is that you (human breathing), cooking, washing, etc are adding moisture to the air. The inside of the windshield gets very close to outside temperature (not double pane). The moisture content of the air inside is higher than the dew point for that temperature and you get condensation.

Yes, opening a vent to exchange some of the moist interior air for outside air with its lower dew point will help, particularly when showering, cooling, etc.

You can also aim a fan at the windshield, though this will serve to also remove heat from the coach. If severe, use a towel to remove the majority of the moisture and then use a fan. Only real long term issue is if there is enough condensation that it runs down the windshield long enough and enough quantity to harm the structure below the windshield. Towels along the dash/windshield junction will prevent that.

Brett

Re: Moisture buildup on windshield using furnaces

Reply #2 – November 24, 2013, 11:15:45 am

Brett: Tks for the reply. I have had two Foretravels 99 and 02 and both had moisture buildup on the windshield from the furnaces. (When on). I usually don't notice it until I pull back the shade. Then I have to wipe it all off to see out well. Surely this does not happen on regular occurrence on all coaches. DAN

Re: Moisture buildup on windshield using furnaces

Reply #3 – November 24, 2013, 11:21:29 am

Greetings

If we shower or cook pasta without the vent open a little.. condensation on the front windows.. sometimes sides.. but we have single pane windows.

Hope our experience helps you!

Re: Moisture buildup on windshield using furnaces

Reply #4 – November 24, 2013, 12:24:49 pm

Dan, I believe it does, it does on mine,

Re: Moisture buildup on windshield using furnaces

Reply #5 – November 24, 2013, 02:42:42 pm

I put a towel down and use a scraper from the shower then hit it with the hair dryer and it dries right up but it has to be really cold out to build up that much.

Re: Moisture buildup on windshield using furnaces

Reply #6 – November 24, 2013, 05:53:33 pm

Keeping a roof vent open a bit helps keep the moisture down - I also have observed that propane furnaces dry the coach out a little more than the Aqua-Hot systems.

Re: Moisture buildup on windshield using furnaces

Reply #7 – November 24, 2013, 09:43:35 pm

Be sure to run the vent when showering, cooking, making coffee, hanger drying clothes or breathing! We have single pane windows and run the fantastic fan for a good part of the day to keep our windows dry.

see ya
ken

Re: Moisture buildup on windshield using furnaces

Reply #8 – November 25, 2013, 04:54:11 pm

I found more with the propane than the aquahot.

Re: Moisture buildup on windshield using furnaces

Reply #9 – November 25, 2013, 05:03:31 pm

John,

Not sure why there would be any difference between propane and aquahot. In both, the "heat source" is external to/separated from the interior air.

Wonder what other factors are afoot?

Re: Moisture buildup on windshield using furnaces

Reply #10 – November 25, 2013, 05:30:35 pm

FWIW,
One thing that I have heard/used is using bubble wrap on the windows. This would be especially helpful if one has single pane windows (like me). This certainly decreases the outside visibility but a lot cheaper than changing out windows. I would recommend that one do it especially on some of the windows where the curtins/shades are usually pulled. I did this some while camping in Colorado during the winter. I usually kept the shades pulled down and could not see out anyway. I think it also helped with insulation/comfort/use of propane.

Re: Moisture buildup on windshield using furnaces

Reply #11 – November 25, 2013, 06:48:44 pm

What cannot be helped is that warm moist air really likes to condense on cold surfaces. People sleeping in tents get wet from the condensate running down the walls, and my previous RV without double glazed windows made good use of the weep holes, and a whole lot of water collected on and below the windshield. Fortunately for me, my Foretravel coach has double glazed side windows, well insulated walls, even insulated skylight and vent cover, so all is dry. My oem windshield blinds roll down and pretty much seal on the sides and bottom, leaving an insulating air pocket next to the cold glass.

My suggestion is to use whatever means available to insulate the windshield and keep a roof vent open so the moisture has someplace to go.

Re: Moisture buildup on windshield using furnaces

Reply #12 – November 25, 2013, 07:06:41 pm

We use a dehumidifier and here on the Oregon coast we have no window water at all even after taking a shower. The inside of out TT is about the same as a 32' coach.

Re: Moisture buildup on windshield using furnaces

Reply #13 – November 25, 2013, 07:29:04 pm

And be aware, driving in real cold weather will cause that moisture to freeze on the windshield unless you have a real good defroster and/or fans blowing on it.

Re: Moisture buildup on windshield using furnaces

Reply #14 – November 25, 2013, 07:56:30 pm

My first trip to Nac with my coach, driving thru La on I-20, weather was warm, then drove into a very cold heavy rain, presto, inside glass fogged over, had to swing my jacket to swipe enough area to keep it on the road, pulled over, got out the window squezy, so could keep it safe to drive.
That is when I realized the defroster position all the way to the right did not include the a/c compressor running. Later while at FOT, one of the techs, splained it to me, you need the NEXT to the last position for both defrost AND a/c effect.
Was too close to a bad outcome, guess why I still recall it from 5 years ago.
Since then no problem, learned how to cope with it

Re: Moisture buildup on windshield using furnaces

Reply #15 – November 25, 2013, 09:56:27 pm

Brett,

Maybe it's the same the furnace in my home - having owned more houses than I care to think about (many transfers) - the gas fired hot air furnace dried out the house a lot more than either the hot water heat systems or even the heat pump units.

My favorite heating system was a radiant hot water system in the concrete floor - man, those ceramic tiles felt toasty in the Ohio winters.

Re: Moisture buildup on windshield using furnaces

Reply #16 – November 25, 2013, 10:08:46 pm

Greetings

We have used the residential 3-M window wrap to noticeable success. Definite difference..see right thru it.. take it off in the spring.

Of course not on the windshield.

Re: Moisture buildup on windshield using furnaces

Reply #17 – November 26, 2013, 01:56:08 am

The air blowing over a hot metal plate dried out the air in coaches enough to dry my eyes out many times.

The older Foretravel Mylar shades and thick blackout drapes kept the moisture build up down a little on the windows but I had to explain many times to prospective customers that the stains on the walls below the windows were not leaks but condensation marks.

Windows were thicker then and the middle slid open as they were three piece. No rattles.

Later windows were bigger and two piece and thinner. Some rattled at times.

And no Mylar.

Bob

Re: Moisture buildup on windshield using furnaces

Reply #18 – November 26, 2013, 06:05:03 am

Don't know why it seemed that way. The AH in the last two units still wet down the windows but my propane furnace on the 99 did it worse.

Re: Moisture buildup on windshield using furnaces

Reply #19 – November 26, 2013, 11:14:10 am

You need to condition the air. A dehumidifier will solve the problem and you will be comfortable at lower temperatures.
I often found a gallon of water in the dehumidifier in the morning.
No wet windows or walls.

Re: Moisture buildup on windshield using furnaces

Reply #20 – November 26, 2013, 06:21:59 pm

Can anyone recommend a specific dehumidifier for use in the coach? I've found a couple of smaller ones but 1st hand experience is always worthwhile.

Re: Moisture buildup on windshield using furnaces

Reply #21 – November 26, 2013, 09:43:00 pm

The one I used has about a one sq. foot footprint.
It sat under the end of the kitchen table. We still had enough room behind it to sit at the table. It has a 1 1/2 or 2 gal water tank.
Dried out the coach. All the difference in the world.
Side benefit, they make heat while working.

Re: Moisture buildup on windshield using furnaces

Reply #22 – November 27, 2013, 08:22:56 am

Quote from: Mark Benko – November 26, 2013, 06:21:59 pm

Can anyone recommend a specific dehumidifier for use in the coach? I've found a couple of smaller ones but 1st hand experience is always worthwhile.

Howdy Mark,
We have used this dehumidifier for several years. It uses solid state Peltier technology. We have been very happy with this product, it is very quiet and does a good job. Link: Amazon.com - Eva-Dry Edv-2200 Mid-Size Dehumidifier

Good Luck, Dave A

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Re: Moisture buildup on windshield using furnaces

Reply #23 – November 27, 2013, 01:03:06 pm

Quote from: Dave and Nancy Abel – November 27, 2013, 08:22:56 am

We have used this dehumidifier for several years. It uses solid state Peltier technology. We have been very happy with this product, it is very quiet and does a good job. Link: Amazon.com - Eva-Dry Edv-2200 Mid-Size Dehumidifier

Thanks Dave. I was looking at that one and was wondering if it was "over kill" or just right. They have a smaller version Amazon.com - Eva-Dry EDV1100 Petite Mini-Dehumidifier but I'm not sure that one would be able to remove enough moisture. I guess I'll go larger since you're happy with that one. Thanks.

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