Roof insulation condensation problem

[goducks]

No way will that soaking wet insulation dry out on it's own even with attic vents of which don't seem to be all that great if you have minimal airflow throughout the RV attic.
I would be asking for a complete new roof along with insulation.

[JohnWedell]

I recommend anyone using their fifth wheel in cold weather remove the trim on the bathroom exhaust fan and feel the foil above the insulation under the roof plywood. The attic is not vented and there is no way for moisture to escape and condenses on the cold foil.

[Rustic Eagle]

Originally Posted by JohnWedell

snip...... Just wondering if anyone has installed the mushroom type vents and if they worked.

I haven't spoke to anyone that has installed them after-the-fact, but have to believe they would provide some degree of attic condensation control. I have seen OEM attic vents on some 5th wheel brands/models (not Jayco).

Definitely wouldn't hurt to have 3-4 attic vents on the roof..., at least I haven't heard of any 'cons' against them.

Originally Posted by JohnWedell

Waiting for Jayco to get back to me about the condensation problem and installing attic vents.......snip

Be interesting how they respond to your inquiry.

Bob

[Magnolia Tom]

I don’t believe adding roof vents alone will do much. On your home, attic vents need intake (soffit) vents to move the air. Without any kind of soffit venting on the trailer , your roof vents won’t move much air. JMHO

[JohnWedell]

Originally Posted by Magnolia Tom

I don’t believe adding roof vents alone will do much. On your home, attic vents need intake (soffit) vents to move the air. Without any kind of soffit venting on the trailer , your roof vents won’t move much air. JMHO

It doesn’t look like there’s much I can do. I guess my future is mold and rot.

[TCNashville]

Any way to get a small fan up there?

[JohnWedell]

Originally Posted by TCNashville

Any way to get a small fan up there?

No but what I did do was remove the trim from the two exhaust fans and placed cardboard over the openings and removed all 6 speakers on the ceiling. When I turn the fans on to draw air through the speaker holes into the attic there was no air movement at all. It appears the entire attic is a dead air space with no ventilation at all. Knowing that now, I doubt if attic vents would do any good at all.

[Rustic Eagle]

I can't confirm level of effectiveness, but for what it's worth a couple Jayco competitors state:

Keystone-Montana 5th wheel: "Two attic vents for cross-ventilation (Four Season Living Package)"

Grand Design-Solitude 5th wheel: "To maximize the effectiveness of the insulation, a vented attic allows condensation to escape the roof structure."

Bob

[JohnWedell]

I’m no expert but everywhere I’ve read says that an unvented attic is a disaster for condensation and mold. I talked to the people at Keystone and they said that’s the reason they vent their attic’s. The Reflectix Jayco uses under the roof plywood seems to be the problem. It gets really cold when the roof gets cold and moisture condensers on it (it doesn’t take much to reach the dewpoint). I really wish Jayco had vented their attic space. Other than that we’re extremely happy with the trailer. Still waiting for Jayco to get back to me hopefully with some kind of an answer.

[Crabman]

So I guess in this case not having the arctic package or foil insulation is actually a good thing? No vents in mine either, but it's just the lowly R7 fiberglass insulation no foil. But it's still a dead air space. I have read where not running the forced air furnace and using electric space heaters can contribute to condensation problems as well. I will have to drop an ac vent next time I cold weather camp and check for moisture. I always leave the bathroom vent with the Maxxaire cover open no matter how cold it is to reduce moisture.

[JohnWedell]

With more and more people full-timing I wonder how widespread the problem is.

[Magnolia Tom]

John

It just occurred to me that maybe you’re getting too much cold air into the attic space because you may have some leaks of the AC system. Specifically the vents. Have you removed the black collars and foil taped the gap between the ceiling and the main duct? That would do 2 very important things... first, you’ll get much better air flow and cooling into the trailer and second, you won’t be sending cold air into the hot attic which could cause the condensation problem.

Just a thought

[JohnWedell]

Originally Posted by Magnolia Tom

John

It just occurred to me that maybe you’re getting too much cold air into the attic space because you may have some leaks of the AC system. Specifically the vents. Have you removed the black collars and foil taped the gap between the ceiling and the main duct? That would do 2 very important things... first, you’ll get much better air flow and cooling into the trailer and second, you won’t be sending cold air into the hot attic which could cause the condensation problem.

Just a thought

I taped up all the ac diffusers and return air plenum. The problem I have is with the temps getting cold outside and warm inside.

[Magnolia Tom]

Originally Posted by JohnWedell

I taped up all the ac diffusers and return air plenum. The problem I have is with the temps getting cold outside and warm inside.

Gotcha...

Seems like the insulation on the ceiling must either be inadequate or improperly installed. The insulation “should” keep the warmth in the rig and not allow it to migrate into the attic. If the attic space is getting that warm, there’s got to be a spot where the insulation is missing or there’s a gap. If you had an IR camera, you could see where the heat was coming from.

The only thing I could think of to help is using some type of mushroom vent with a built in fan to actually draw out the air but not sure that would work.

Edit:
Do you have condensation on the ceiling during the summer? If so, that location is where your insulation problem is.

[JohnWedell]

There is no condensation in the living area at anytime. in the winter or summer there is no condensation even on the windows because we use a dehumidifier to keep the humidity low inside the trailer and wipe down the shower with a towel. The reflexit is under the plywood on the roof above the insulation. It gets really cold and causes condensation.

[Magnolia Tom]

Originally Posted by JohnWedell

There is no condensation in the living area at anytime. in the winter or summer there is no condensation even on the windows because we use a dehumidifier to keep the humidity low inside the trailer and wipe down the shower with a towel. The reflexit is under the plywood on the roof above the insulation. It gets really cold and causes condensation.

I understand where you are getting the condensation and why.
My point is if you were not using the dehumidifier, you’d see the condensation on the ceiling during the summer and it would show you where your problem is. Somewhere you’ve got an insulation problem imho.

In the summer, when the attic is hot and the inside is cold, where the insulation is lacking condensation would form on the ceiling. The use of the dehumidifier is preventing the condensation to occur.

In the winter, when the trailer is warm and the attic is cold, condensation forms on the roof’s reflectix. So, if you were to put a dehumidifier in the attic during the winter, there wouldn’t be condensation on the reflectix either.

[JohnWedell]

Correct but the attic is a dead air space with no airflow. Each bay is sealed off with insulation with no room above it.

[Magnolia Tom]

Originally Posted by JohnWedell

Each bay is sealed off with insulation with no room above it.

This is where I think you could be mistaken. I think you’ve got a void somewhere. Only way to know for sure is get a thermal camera. Good luck

[JohnWedell]

The condensation is under the entire roof.

[Magnolia Tom]

The condensation is on the entire roof because the warmth is migrating into the attic space from one or more voids in the insulation.