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lawrosa's avatar
lawrosa
Explorer
Dec 09, 2018

skylight condensation

Living in my 26ft coachmen for the past 6 months now. Im in Myrtle beach.

Just noticed water droplets on membrane between ceiling and skylight bubble.

its colder here and running electric heat past several weeks.

Noticed it last week too and little plastic membrane that is sticky tapped to ceiling besel was unattached on one side. ( Possibly shower steam made sticky tape non sticky)

I pulled besel down and whole bubble was wet with large droplets. roof membrane folded over so drops were collecting in ceiling collar. No damage except small edge of luan damp.

Upon removal I see the back roof truss is open and I can see back wall of camper. Slight dew on nails and wall membrane on back wall.

I would think the heat from in the camper it getting through they membrane and interacting with the cold air in the bubble skylight and condensating..

Im thinking to insulate all gaps and openings around roof trusses with collar removed. Then put that membrane back but seal it to the collar with silicone.

Is that my best bet?

I could of course leave the membrane off too. as this is how I have it now so I can watch it a few days until I get some insulation.

Possibly spray foam may be better but I probably will just get a bag of the soft stuff.

So is my plan feasible? Anyone have this issue?

29 Replies

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  • lawrosa's avatar
    lawrosa
    Explorer
    Dec 09, 2018
    I know this is a fan pic. but it shows the wood boxed out around the opening.

    Since I have an arched roof i have a gap between the wood and the trusses.

  • lawrosa's avatar
    lawrosa
    Explorer
    Dec 09, 2018
    Its a bathroom skylight like this

    At the top is a plastic film. I removed the plastic film for now. Now I have direct view of the bubble skylight.

    Its the bubble that had the condensation on the underside..

    Now when I had the bezel removed you can see the roof trusses. Its the roof trusses that have no insulation on one side. So its kind of open like an attic. ( Ill try to find a pic of that.)

  • pianotuna's avatar
    pianotuna
    Nomad III
    Dec 09, 2018
    Hi,

    If you do use foam get the low expansion type.

    What to do about condensation?

    The cause of the condensation is the walls are below the dew point temperature. If the walls can be made warm enough the problem disappears. Running a fan to circulate air may help to raise the temperature on the surface of the wall.

    One other solution is to reduce the relative humidity inside the RV.

    The easiest way to do that is to open a roof vent a bit, find the furthest window from the vent and open that a bit. An electric heater near the window will improve that and keep you warmer. I'd suggest a low wattage radiant type, or a small oil filled (if the oil filled can be on a shelf so the air from the window passes over the fins.)

    I know opening a vent and window when it is cold seems counter intuitive, but it does work.

    Another possible solution is an electric dehumidifier--but the cooler it is the poorer they work. They are generally energy hogs, some what bulky and definitely noisy.
  • enblethen's avatar
    enblethen
    Nomad
    Dec 09, 2018
    Sounds like the skylight is not sealed. You are getting moisture from inside the rig to between panels of skylight.Not sure what your installation is like and how to reseal. There is no where for the moisture to escape to the outside, so it stays.
    If this is in bath, you need to get a better exhaust fan so moisture does get into skylight. Fantastic fan
    Do you have covers and leave your vents open? If not get covers and leave the vents open at least a couple of inches at all times.
  • Lwiddis's avatar
    Lwiddis
    Explorer II
    Dec 09, 2018
    “No damage except small edge of luan damp.”

    You hope but I don’t think so. Time for a complete inspection, repair and sealing. As Don said, lower the humidity.
  • lawrosa's avatar
    lawrosa
    Explorer
    Dec 09, 2018
    donn0128 wrote:
    Lower the humidity inside.


    Unfortunately thats not a good answer..Thanks anyway.

    I don't have condensation issues anywhere else.

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