Another case of black mold in an Outdoors RV

[keymastr]

Foam core roof does not allow for ducting the air conditioner which is a must in larger luxury units. No way do I want a noisy AC going on and off all night above my head when I could switch to the one at the other end of the trailer and let it work through the ducts.

In both of the examples given they mentioned water pouring from a light fixture. If you have that much water in your attic space you either have no moisture control in the form of venting or dehumidifier or you have a leak. Either of those things can happen no matter what construction method is employed.

I am full time and we never have frost on windows, walls or anywhere else. No moisture dripping anyplace. No wet wood under the mattress or the back wall of the cabinets and we are in the Seattle area where typical humidity is between 70 and 95%. My indoor humidity is at 30% right now with an outside humidity of 86%.

If you boil water without using the vent fan or shower without using a good exhaust vent like a Maxx fan or Fantastic fan that moves enough air to actually pull the water vapor out then you are going to have issues, and if you live where there is already a lot of humidity in the air you MUST use a dehumidifier. Mine is a Vremi unit that is sized for a 4000 square foot home and pulls several gallons of water out of the air each day. If you are not controlling the moisture you will have issues.

[LBZYA]

The easiest solution for ORV is to fill the roof cavity with spray foam before sheeting the roof. Thermal break and sealed achieved.

[Rick 1947]

Very interesting thread. Thanks to all. We have a OVR 2016 270cisw. Can’t help but think the problem is solely ceiling ventilation (cross ventilation). Putting a timeframe on the number of days, weeks or months one can reside in an rv, seems to defeat the purpose of use. For you full timers, ouch! I’m truly exploring cross ventilation retrofit.

[ColoradoRFL]

Originally Posted by keymastr

Foam core roof does not allow for ducting the air conditioner which is a must in larger luxury units. No way do I want a noisy AC going on and off all night above my head when I could switch to the one at the other end of the trailer and let it work through the ducts.

In both of the examples given they mentioned water pouring from a light fixture. If you have that much water in your attic space you either have no moisture control in the form of venting or dehumidifier or you have a leak. Either of those things can happen no matter what construction method is employed.

I am full time and we never have frost on windows, walls or anywhere else. No moisture dripping anyplace. No wet wood under the mattress or the back wall of the cabinets and we are in the Seattle area where typical humidity is between 70 and 95%. My indoor humidity is at 30% right now with an outside humidity of 86%.

If you boil water without using the vent fan or shower without using a good exhaust vent like a Maxx fan or Fantastic fan that moves enough air to actually pull the water vapor out then you are going to have issues, and if you live where there is already a lot of humidity in the air you MUST use a dehumidifier. Mine is a Vremi unit that is sized for a 4000 square foot home and pulls several gallons of water out of the air each day. If you are not controlling the moisture you will have issues.

If you watch the video I linked they show a large dehumidifier in their shower which they claim is running full-time. However, everyone here seems to be talking only about relative humidity not absolute humidity.

Relative humidity in a trailer is going to be much higher in the cold attic than it is in the bathroom. That is because cold air doesn’t hold as much water vapor as hot air. If they set their dehumidifier in cold snowy Vermont at let’s say 45% in their rv bathroom (we have essentially the same trailer design and bathroom is warmest spot in trailer when heater is on) extreme cold outside temperatures will set the dew point into their attic to a much lower temperature.

When the 45% humidity air at 70 degrees hits that cold attic air it turns to water.

[ColoradoRFL]

To clarify, if the outside temperature is 10 degrees, the attic at anything below 57 degrees will turn vapor to water when the moderately humid inside air around 50-60 hits the attic because the colder temperature means the air is condensed and cannot hold that amount of water.

My point is the problem is likely the outside to inside temperature extremes and not the fact two people are creating humidity in the trailer. Seattle doesn’t get that cold therefore the previous poster full timing in the same trailer in Seattle won’t have this problem.

It will be an interesting test to attach a remote temperature and humidity sensor to the inside ceiling of the attic space. My guess is below a certain outside temperature you will have the dew point in the attic creating mist while the humidity inside the fully heated areas will remain normal.

[Rick 1947]

Concur with your assessment. In a response above, I misspoke when I suggested ceiling cross ventilation. Actually I meant attic cross ventilation. I have only found one, what I assume is a mushroom type attic vent at the rear portion of the roof on our 270cisw. It seems to me that an additional vent (or vents) should be located to allow moisture to escape. Or, perhaps a Venturi type vent that would allow the same. Just a thought.

[ColoradoRFL]

Originally Posted by Rick 1947

Concur with your assessment. In a response above, I misspoke when I suggested ceiling cross ventilation. Actually I meant attic cross ventilation. I have only found one, what I assume is a mushroom type attic vent at the rear portion of the roof on our 270cisw. It seems to me that an additional vent (or vents) should be located to allow moisture to escape. Or, perhaps a Venturi type vent that would allow the same. Just a thought.

Another approach would be to stop cabin air from getting into the “attic” when the heater is running. As with any permanent structure in extremely cold regions, allowing air to enter the attic from your living quarters causes condensation as this one HVAC expert advises for homeowners -

“The primary cause of your attic-moisture problems results from warm air escaping from the heated portion of your home into the unheated attic space”

We camped in Leadville, Colorado once when temperatures dropped to -20 degrees. We used to take our Class A National RV Tropical skiing with our sons. At -20 the “attic” was weeping water all night.

[egwilly]

Originally Posted by Rick 1947

Concur with your assessment. In a response above, I misspoke when I suggested ceiling cross ventilation. Actually I meant attic cross ventilation. I have only found one, what I assume is a mushroom type attic vent at the rear portion of the roof on our 270cisw. It seems to me that an additional vent (or vents) should be located to allow moisture to escape. Or, perhaps a Venturi type vent that would allow the same. Just a thought.

Ideally you could have two roof vents, both with small dc fans, one at each end. One running to push air in, the other pulling the air out.

If I was camping in these conditions, I would be looking into getting as much air circulating up there as possible. I don't camp in the snow. I have no experience with this at all. I just know that moving air is helpful.

[bneukam]

The trusses are completely filled with batten insulation. There are no baffles for air to travel to get to these small vents.

So as heat and water vapor rise, the thought of pulling this air towards the vents is very hopeful thinking.

By installing fans you could actually be increasing the draw into the attic from the living space, making the issue worse.

For many years this type of TT roof construction didn’t have vents. I am not convinced they aren’t making the issue worse.

Can anyone post a photo of one of these vents on the roof. How many are there? What do they look like?

[Brad Wilf]

Like this on ORV's anyways, mushroom attic vents. Mine only has one, above rear kitchen area. if anything I would install another towards the front of the rig, in the hopes of better air movement.

[bneukam]

Grand Design used to advertise on their website, with photos of massive vents that stated “gets rid of unwanted moisture”.

It’s now no longer posted, probably received too many questions.

Sorry, but vents are important feature on a house, but in a trailer with very little clearance, and cavities filled with fiberglass insulation, venting is not going to solve this issue. If it does help it’s very minimal at best.

[Cumminsfan]

Originally Posted by bneukam

Grand Design used to advertise on their website, with photos of massive vents that stated “gets rid of unwanted moisture”.

It’s now no longer posted, probably received too many questions.

Sorry, but vents are important feature on a house, but in a trailer with very little clearance, and cavities filled with fiberglass insulation, venting is not going to solve this issue. If it does help it’s very minimal at best.

I've seen some videos of GD's roof build process. Inadvertently they would seem to fare better. While they tout high R values, they in fact are sloppy on the insulation process. The videos/pics I've seen show gaps in the insulation all along the outer edges and other areas. That would allow better air flow.
GD owners clearly ar not getting the R40 they advertise but they probably aren't having as many issues with mold.

Whats interesting though is that of all the RV forums I read, I've only seen a mold issue from an attic pop up on the ORV forum.

It's either not a known issue or it's a perceived issue that would be dependent on usage and how tight the attic is packed with insulation.

Or it could be an ORV design problem.

[camper8251]

I wonder if the reason it has only shown up in the ORV forum is because the buyers of these units are buying them based off the 4 season capability?

I had an AF truck camper and camped a lot in the winter with it prior to this unit and as far as I know did not have any mold issues. But we did vent the heck out of it when camping in the winter and cooking in it. We did not take showers though in the winter time.

Never really compared the build of the roof vs ORV either...

[bneukam]

Originally Posted by Cumminsfan

I've seen some videos of GD's roof build process. Inadvertently they would seem to fare better. While they tout high R values, they in fact are sloppy on the insulation process. The videos/pics I've seen show gaps in the insulation all along the outer edges and other areas. That would allow better air flow.

GD owners clearly ar not getting the R40 they advertise but they probably aren't having as many issues with mold.



Whats interesting though is that of all the RV forums I read, I've only seen a mold issue from an attic pop up on the ORV forum.



It's either not a known issue or it's a perceived issue that would be dependent on usage and how tight the attic is packed with insulation.



Or it could be an ORV design problem.

Well you know that I have been discussing this potential problem since 2018 on this forum.

I’ve seen it for myself on a friends ORV unit that they were living in for a short period, while helping them renovate their house. Yes it was during late fall/ early winter in Montana. First sign was a very small brown water stain on the ceiling trim piece. Mold was only in the attic above bathroom/kitchen area.

For the most part what I posted back then was largely ignored. But I think now many are starting to pay attention.

Mold especially in a small space can be a serious health hazard. Remember back after Hurricane Katrina when temporary housing was brought in with this same type of construction, and the majority of them suffered the same problems.

How big of a problem is it? Well how many people actually go in and pull down the batten insulation to inspect. Not many is my guess.