Originally Posted by Gerry
But lets all remember a by-product of propane
is moisture so it is important to have air flow to allow this moisture to escape
Anywhere there is cold air on one side and warmer air on the other moisture will be present...A vapor barrier needs to be put in between these 2 air masses in the form of plastic sheeting but the low grade window will also collect and drip water down on inside or warm air space
The OP said he "plugged in" a heater. That is not propane
and it is not creating a moisture problem the way a propane heater does.
However an electric heater won't solve all the moisture problems and it is good to say why that is so instead of just posting a one sentence statement that might leave people wondering why it is true. You still have moisture coming in, then it gets warmed by the heater and then it is hitting that cold glass on the windows
and other surfaces which are below the dew point temperature and that is causing the water to condense which is leading to that puddle. So put some Reflextic insulation over that glass to keep the warm moist air off of it if you are only going to use occasional heat.
Basically every time you turn on a heater in a really cold space that is below dew point temperature you will have warm moist air hitting surfaces that are cold enough to condense moisture. Fresh air movement in and out without heat can do a better job than occasional heat.
If you really want to dry the air out and you have electric available then get a dehumidifier than has a drain tube and connect it to a drain that goes to the outside. The dehumidifier has its own internal heater and it causes the condensation to happen within the unit instead of on the surfaces in your RV. Get a good quality one. Be careful about buying a used dehumidifier as in the last few years quite a few brands had recalls on them. It is not good to leave them running without supervision for long periods of time. So if you are going to turn one on be sure to go back in a few hours and turn it off or have it on a timer that will turn it off.
Note to everyone: It is a good idea to check for recalls before using older dehumidifier units as yours might have one that you did not get notified about.
Hint for a temporary outside drain to hood a dehumidifier to:
Your fresh water tank likely is hooked to a spigot that drains underneath your RV. As it is winter you might have winterized your water system and drained that tank. During the winter you could borrow that drain spigot for a dehumidifier drain hose. Or of course you could just find a spot inside a cabinet and install a dedicated stop spigot for use with the dehumidifier.