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Window Condensation


lappir

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Nice cool morning here in North Florida and I have significant condensation on all of my windows. I know most of it is my fault and am asking if there are ways that I am not aware of to help reduce. I have read most of the information and comments on the moisture in the cabinets thread and have even commented on the topic regarding how condensation forms.

 

I hadn't noticed the significance until last year when cleaning my windows and uncovered a usually closed blind with a couple pieces of Reflectix to ward off the suns rays had caused a significant growth of some fuzzy creatures on the window glass. I now look behind those areas more frequently and today found quite a bit of moisture on the glass. I have cleaned most of the windows in my trailer so far this morning and have noticed little condensation reforming with the blinds raised. I have prepared breakfast but haven't taken a shower yet so the humidity may not be at it's highest point of the day yet.

 

I have a Heat Pump for my primary heating and cooling functions. It's a basement model with the output across the center of the ceiling and a return in a hall from the kitchen to the bed/living room. I also use an iHeater 1500 at night since the Heat pump blows out rather cool air for the first minute or two (it seems) and will wake me if I have exposed skin to the not yet warm air movement. During the daytime it doesn't bother me.

 

I much prefer the cold to being HOT so that and the fading effects of the sun on things are why I have my blinds closed over 90 percent of the time. My hope to have the perforated film applied to my windows last year didn't materialize. I left my name and location with the installer at last years Tampa rally but apparently there were not enough people needing it in Wellington to have him call me and put me on the list. Hopefully this year I can get it done. For the next couple days with the overnight temps forcasted for the mid to low 30's I guess I will keep the thermostat a bit higher than usual, keep the blinds up and wipe down the windows before they drip down the walls. For those who may suggest opening a roof vent, I cannot. There is nothing on the roof of my trailer except three tank vents and on my next trailer (if it happens) there will only be one.

 

Thank you in advance for any suggestions or comments.

Rod

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Less humidity and warmer are of course your best bets for window condensation but there are other options.

 

They make some stick-on storm windows that go on the inside of the rig that are pretty nice. A roll of double-stick tape to put around the window outside the frame and then a layer of plastic to apply to that. Some are just elastic and you pull them tight before sticking down, some are heat shrink, either works just fine. A really nice thing is that they also cover the window frame and seal any air infiltration. We have tried them a couple times and both types we had peeled off easily at the end of the season.

 

A downside to this is that without the storm windows your glass is acting as a dehumidifier, seal it up and the moisture will build up and start condensing elsewhere, often out of sight and un-noticed.

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Single pane windows have an R-value of ~0.9 (essentially nothing). Therefore the interior surfaces of the window (and the surrounding frame) are pretty much at outdoor temperature. For any particular temperature and humidity combination in your RV, the dew point (which you can look up) will be the temperature at which water condenses out of the air. When the outside temperatures drop below the inside dew point you will get condensation on the inside of your windows.

 

Condensation on windows does not necessarily mean you are getting condensation elsewhere in your RV. As long as the temperatures in "spaces" within your RV remain above the dew point there shouldn't be condensation. But closed up cabinets and closets against outer walls can get quite chilly.

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Even in high humidity areas I always try to keep a vent open to let out the moisture generated from cooking, showering and just breathing. Seems to help.

 

In the spring (May) I am usually at a mountain lake in Eastern Oregon (5000 foot level) without any hookups and I use a propane "brick" heater. It generates huge amounts of water vapor. Keeping a window cracked and an overhead vent open prevents large amounts of condensation from building up.

 

Lenp

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I use a propane "brick" heater. It generates huge amounts of water vapor. Keeping a window cracked and an overhead vent open prevents large amounts of condensation from building up.

 

 

 

Unvented propane heaters add moisture because the combustion products of propane are CO2 and water. It's a common misconception on these RV forums that all propane heaters add moisture, but that is totally false for those that are vented. In fact, if the combustion system uses heated room air and then vents its exhaust the net effect is to bring cold air in which results in lowering the moisture level in the heated space.

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.... In fact, if the combustion system uses heated room air and then vents its exhaust the net effect is to bring cold air in which results in lowering the moisture level in the heated space.

I can't recall ever having seen one like that. Vented and unvented are pretty common but that would seem to be a hybrid. Got a link to someone who makes one of them?

 

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I can't recall ever having seen one like that. Vented and unvented are pretty common but that would seem to be a hybrid. Got a link to someone who makes one of them?

 

 

Many vented heaters use room air for combustion and then exhaust the output stream through a vent stack. That's essentially what almost all gas fireplaces do. Providing a separate stream of outside air for combustion requires a second vent line. You find those on high efficiency home furnaces.

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I guess I hadn't thought of the radiant heaters or the catalytic ones. For homes around here the wall mounted, single penetration version such as this one from Lowe's or Home Depot is very common. Those actually work very much like an RV furnace. Getting back to RV's the Olympian catalytic has been pretty popular with the boondocking folks.

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Turned the temperature up to around 68 last night when hitting the bed. Left the blinds up in the rooms where I wasn't sleeping and left it 1/3 open in the bedroom. Had minimal condensation this morning. Guess I just need to have the heat getting to the windows and the condensation won't form. Don't like the sun still so will need to close them during the day.

 

Rod

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Many vented heaters use room air for combustion and then exhaust the output stream through a vent stack. That's essentially what almost all gas fireplaces do. Providing a separate stream of outside air for combustion requires a second vent line. You find those on high efficiency home furnaces.

It's called a concentric vent, I had one. One vent is inside the other. They have to be angled down towards the outside so vapor condensing can run out he end of the pipe.

 

Turn up the heat pump a bit.

 

I'm in Victoria currently 42 f and 85% humidity. I use both heat pumps and set them on heat for no lower than 65f. Even when it gets down to 27f outside and I switch to the propane furnace and cube heaters, I don't have condensation issues.

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