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Topic: Condensation on over-cab roof vents (Read 16 times) previous topic - next topic
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Condensation on over-cab roof vents
Yahoo Message Number: 109723
Hello fellow RVer's:
 We are the proud owners of a 2005 26.5 mid-bath, and have been thoroughly enjoying it for the last week or so.  We have noticed that there is a what I would call a "normal" amount of condensation each morning on the windows (no doubt due to the icy cold Oregon air outside).  However there seems be what I would call an excessive amount on the over-cab roof vent each morning, even causing it to drip a little bit.  I know it is not leaking, as we've had a lot of rain (morning, new and night) and it doesn't leak other than first thing in the morning.

Any ideas?  Is this a common occurrence?

Thanks for your help.

Corey
Re: Condensation on over-cab roof vents
Reply #1 –
Yahoo Message Number: 109724
wrote: Any ideas?  Is this a common occurrence? --- Yes, condensation build-up, particularly on the aluminum frame of the overcab vent, is common when there are big differences between the inside and outside temperatures.  "Drips" can be even more of a problem when one or two are sleeping up there.
 You might want to click on the "Searchable Archive" link on the home page of the message board; use the keyword "condensation", and many posts on this topic will come up.

Joan
2003 TK has a new home
Re: Condensation on over-cab roof vents
Reply #2 –
Yahoo Message Number: 109725
Thanks Joan:

With the searchable archive, I found lots of great info on my "issue".  Glad to know it's not leaking, and the problem can be easily fixed. I'm calling LD right now, and ordering some vent covers.
Thanks for pointing me
Re: Condensation on over-cab roof vents
Reply #3 –
Yahoo Message Number: 109726
Hi, Corey,

Before you put the vent cover in place, you might consider cutting a 2" think piece of Styrofoam insulation to wedge-fit into the opening.  You'll have to cut a little inset for the vent crank to fit into.
That, plus the cover, has eliminated the condensation problem for us.

Ted H.

'05 RB  NE-13

@ Tyndall AFB, FL

www.wxtoad.com http://www.wxtoad.com/>

I'm calling LD right now, and ordering some vent covers.
Thanks for pointing me in the right direction!

Corey

[Non-text portions of this message have been removed]
Re: Condensation on over-cab roof vents
Reply #4 –
Yahoo Message Number: 109727
On 02/05/2010 9:11 AM, Ted H wrote:

Quote
            Before you put the vent cover in place, you might consider cutting a 2" think piece of Styrofoam insulation to wedge-fit into the opening.  You'll have to cut a little inset for the vent crank to fit into.
That, plus the cover, has eliminated the condensation problem for us.
That's a good idea, Ted. Another thing that helped for me was to cut a piece of reflectix the size of the opening, and then slip it between the hatch cover and the metal slats, which holds it in place. It keeps the cabover area much warmer (or cooler, in the summer), and reduces the condensation. Also, when I want to crank the hatch open for a bit for ventilation, I don't have to remove the reflectix, it just stays in place against the underside of the vent cover.

Fern
Fern Horst
Formerly owned:
1979 TK - "Dorie" (2007-2012)
2003 MB - "Absaroka" (2012-2019)
Re: Condensation on over-cab roof vents
Reply #5 –
Yahoo Message Number: 109730
Quote
Hello fellow RVer's:
 However there seems be what I would call an excessive amount on the over-cab roof vent each morning, even causing it to drip a little bit.  I know it is not leaking, as we've had a lot of rain (morning, new and night) and it doesn't leak other than first thing in the morning.
The key is to reduce as much as possible the amount of moist air that will contact cold parts of the frame. We do that with a custom cover I made that provides a near-hermetic seal to the ceiling, fills the opening with insulation to reduce circulation further, and traps any remaining small amount of condensation from the contained air. I admit that so far it has not received extensive testing, but based on past experience with my other 'solutions' (and sound theory), it should work well. So far, limited experience has resulted in no condensation at all.

Steve
2004 FL
2013 Honda Fit
Re: Condensation on over-cab roof vents
Reply #6 –
Yahoo Message Number: 109731
"you might consider cutting a 2" think piece of Styrofoam insulation to wedge-fit into the opening"

Ted I insulated the hatch by gluing two layers of foam to the bottom of the hatch. This eliminates the need for a separate piece of foam.
The real advantage is that insulation is on duty all the time, working in both the summer and winter.
The foam also blocks any light that may get through the plastic hatch, helping to keep the bunk area darker.
http://www.flickr.com/photos/lwade/sets/72157602104741565/>
 I added more insulation the hatch cover and bunk window covers by sewing quilted insulation from "Warm Windows" to the back of each cover.
http://www.warmcompany.com/wwpage.html>

Larry

Raining in SoCal
2001 MB
* Not to be confused with Larry W (3000 of my posts are actually from expert Larry W due to Yahoo transition mis-step)
Re: Condensation on over-cab roof vents
Reply #7 –
Yahoo Message Number: 109732
Quote
"you might consider cutting a 2" think piece of Styrofoam insulation to wedge-fit into the opening"
Larry, I considered doing this, but does it really prevent most condensation if you are sleeping in the bunk with the vent closed? Unless you keep it pretty warm inside, I would still expect the metal parts of the frame to get cold enough to cause the condensation, even if the vent lid does not.

Steve
2004 FL
2013 Honda Fit
Re: Condensation on over-cab roof vents
Reply #8 –
Yahoo Message Number: 109733
When we were in Oregon, and other cold, wet places last autumn, the vent over the overcab bed got a bit of coalesced condensation on it, but not enough to actually drip.  I kept a terry washcloth under my pillow, and when I woke up, I just wiped down the frame of the opening.  The coldest temperature in the overhead bunk was just about 32 degrees.  This probably would not be sufficient if the weather was much colder than we were experiencing, but it worked for me at that particular time.

Virtual hugs,

Judie Not quite so grounded in Sierra Vista, Arizona
Re: Condensation on over-cab roof vents
Reply #9 –
Yahoo Message Number: 109735
wrote:

When we were in Oregon, and other cold, wet places last autumn, the vent over the overcab bed got a bit of coalesced condensation on it, but not enough to actually drip.  I kept a terry washcloth under my pillow, and when I woke up, I just wiped down the frame of the opening.  The coldest temperature in the overhead bunk was just about 32 degrees. This probably would not be sufficient if the weather was much colder than we were experiencing, but it worked for me at that particular time.
--- The "low-tech" method works for me, too! I sleep in the overcab bed, and unless it's really pouring and blowing, I always have the vent open a little for air! I use a terry cloth shop towel to mop any condensation that collects during the night off the frame and stow the damp towel in a ziplock at the head of the bed area; hang up the towel to dry out (as much as possible) during the day, and it's good for another round of mopping.
 The versatile shop towel, both the blue paper and the terry cloth, are indispensable for RVers; if I had the slightest bit of poetic talent, I would compose an "Ode to the Humble Shop Towel"! ;-)

Joan
2003 TK has a new home
Re: Condensation on over-cab roof vents
Reply #10 –
Yahoo Message Number: 109736
Quote
The "low-tech" method works for me, too! I sleep in the overcab bed, and unless it's really pouring and blowing, I always have the vent open
With Nancy and I sleeping in the bunk - along with both our cats - there is simply too much moisture collecting. True it seems slightly better with the vent open a bit, but then there's a shower when we close it. Best just shutting off the air supply to the vent - we get plenty of ventilation by leaving the cabover side windows cracked open.

Steve
2004 FL
2013 Honda Fit
Re: Condensation on over-cab roof vents
Reply #11 –
Yahoo Message Number: 109743
Corey, I did what Ted H. did.  I have a rectangle of 2" pink styrofoam that I cut carefully so that it is a tight friction fit into the recess for the vent.  I added 1/4" x 1" foam tape on top of the styrofoam to improve the seal when in place.  I cut a notch into the top of the styrofoam for the crank handle.

I had been having condensation dripping onto the upper bunk area. since installing the styrofoam, not a drop.  If any condensation does form, it tends to land on, and stay on, the styrofoam.  I have learned to have a rag handy if I am in damp, cold weather so that when I take the styrofoam down I blot up any condensation that is on the styrofoam.  The only downside to this approach that I know of is having pink showing up there.  That is a bit of a color clash.  When I find the right paint color, I will solve that issue.

As a second benefit, before doing this my vent crank would occasionally vibrate loose so that the vent could open a bit while I was driving.  The foam locks the crank so that no longer happens.

On a related subject, I had been getting condensation on the window frames of the various windows.  Over the cab, it was bad enough that it would drip down the wall.  I realized I had a problem when I felt dampness under the mattress on the front driver's corner of the bed area.  I bought black foam weatherstripping 1/2 inch wide and ran two parallel strips along the frame.  That pretty much covered the exposed frame area and is almost unnoticeable.  Since then, there has been no more evidence of moisture in that area.  Caveat - I am now in a much dryer part of the country so this treatment has not had a real test yet.  I expect the real test to come this spring in Oregon.

Ken F. in NM
'08 MB
Re: Condensation on over-cab roof vents
Reply #12 –
Yahoo Message Number: 109745
Here's a general comment on the various escape hatch condensation-prevention schemes that have been proposed here.
 Plugging the vent is better than nothing, but as others have pointed out, the primary source of condensation is the metal frame. Even with an insulated interior plug, the exposed portions of the frame can still become very cold, leading to condensation. Conversely, if you keep moist interior air away from the frame, condensation won't occur.
 That means a cover that overlaps onto the ceiling, insulating not only the interior but also the edges of the frame, is the surest solution. The LD factory sells just such a cover, made of heavy ivory-colored vinyl with a polyurethane foam backing. It snaps into place, and when not needed, it folds flat (1/2" thick) for storage, making it a lot more practical to store than a large slab of rigid foam. (In warm weather, I store my escape hatch cover flat against the overcab ceiling at the foot of the bed, where it's held in place by an "X" of thin elastic cord.)
 Based on three years of experience in all climates (including long-duration cold, damp weather back east), the factory cover *entirely* prevents condensation. I don't have to keep a rag by my bed. :-) The key is keeping all moist air away from the frame. No interior plug can do that.

Andy Baird http://www.andybaird.com/travels/
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Condensation on over-cab roof vents
Reply #13 –
Yahoo Message Number: 109749
Quote
The LD factory sells just such a cover, made of heavy ivory-colored vinyl with a polyurethane foam backing. It snaps into place, and when not needed, it folds flat (1/2" thick) for storage, making it a lot more practical to store than a large slab of rigid foam.
The cover I built uses the same idea, but I wanted it to be rigid when in use. I built an ultra-lightweight wood frame which snaps to four door magnets mounted inside the hatch frame. I then stretched impermeable 'blackout' material to the frame and glued it in place. When inserted, the soft blackout material seals against the metal frame trim, providing a smooth surface about 3/16" thick. It will contain any condensation that might occur on the vent-side, but I also added a couple layers of cut-to fit Reflectix that push into the vent first. The cover and insulation come apart and roll into a package that is easy to stow if ventilation is desired.
 Certainly a lot more work to engineer, build, and use than the snap-in cover, but I do like the seamless appearance of the result.

Steve
2004 FL
2013 Honda Fit
Re: Condensation on over-cab roof vents
Reply #14 –
Yahoo Message Number: 109755
"The cover and insulation come apart and roll into a package that is easy to stow if ventilation is desired."

Steve

Do you have a photo of the cover?

Larry
2001 MB
* Not to be confused with Larry W (3000 of my posts are actually from expert Larry W due to Yahoo transition mis-step)
Re: Condensation on over-cab roof vents
Reply #15 –
Yahoo Message Number: 109760
From: Andy
 Sent: Saturday, February 06, 2010 12:40 PM
 To: lifewithalazydazerv@yahoogroups.com
 Subject: [LD] Re: Condensation on over-cab roof vents

Based on three years of experience in all climates (including long-duration cold, damp weather back east), the factory cover *entirely* prevents condensation. I don't have to keep a rag by my bed. :-) The key is keeping all moist air away from the frame. No interior plug can do that.

Andy Baird http://www.andybaird.com/travels/

The factory vent cover works because it insulates the cold bare aluminum from the warm moist air within the LD. The insulated foam plug will work too, IF one covers the aluminum flange with 1/8" self-sticky white felt or white or white closed cell foam insulation. Think I'd go with the white felt.

bumper snowing in Minden, NV Yonder

[Non-text portions of this message have been removed]
bumper
"Yonder" '05 MB
"WLDBLU" glider trailer
Re: Condensation on over-cab roof vents
Reply #16 –
Yahoo Message Number: 109761
Quote
Do you have a photo of the cover?

Larry
I searched, but gave up and headed out with my camera. I uploaded to a photo album called 'aq433 vent cover', on the group photos.
 Frame is made of 1" L-cross-section wood trim, and the retainers I routed u-channels from simple trim strips.

Steve
2004 FL
2013 Honda Fit
Re: Condensation on over-cab roof vents
Reply #17 –
Yahoo Message Number: 109762
"The insulated foam plug will work too, IF one covers the aluminum flange with 1/8" self-sticky white felt or white or white closed cell foam insulation."
 You're right, that should work fine. I think the factory cover looks tidier, though.. and it's less likely to be accidentally rubbed off by someone getting up in the middle of the night. :-)

Andy Baird http://www.andybaird.com/travels/
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
 
Re: Condensation on over-cab roof vents
Reply #18 –
Yahoo Message Number: 109769
Precisely, Andy.  That's why my OP mentioned putting the Styrofoam plug in place and then using the LD vent cover.  Ted

Plugging the vent is better than nothing, but as others have pointed out, the primary source of condensation is the metal frame. Even with an insulated interior plug, the exposed portions of the frame can still become very cold, leading to condensation. Conversely, if you keep moist interior air away from the frame, condensation won't occur.
 That means a cover that overlaps onto the ceiling, insulating not only the interior but also the edges of the frame, is the surest solution.

[Non-text portions of this message have been removed]