Interior Condensation

[TheNextBillGates]

Hey guys,

Well, I'm stuck in the cold for a while...I have my external LP tank hooked up and we're managing to stay rather toasty! My 38J has a rear bedroom we can close the door and a small electric heater keeps us toasty at night while the coach thermostat stays at 50. During the day I crank it up to 70. If we're lucky, it gets warm enough to use the heat pump.

My issue is with condensation. As most have seen at some point, we saw moisture on the windshield and window frames. I bought a dehumidifier and sat it in the front of the coach and it has all but eliminated the excess moisture. However, certain areas of the coach are still problematic:

- In the shower, there's about 1" of wall that I can see between the top of the shower and the roof. It is VERY cold (lack of insulation I suppose) and condensates heavily during a shower.
- The closet is located on the passenger side rear corner. The top right corner (top rear corner of the coach) is VERY cold and condensates as well. This is a section at least 6" tall and 2' wide. This causes our clothes to get wet.
- The lights in the closet come through the ceiling. Condensation drips from these holes & wires and short out the closet lights. This is not a leak from the exterior, only condensation and only during the winter.
- The bottom corners of our slides are very chilly. Since Winnebago used a lot of fake wood with wood grain contact paper on it, we're getting several areas where the wood grain is peeling off due to the moisture.

In the end, I'm a little upset that the coach isn't a sealed up a bit better. But, I suppose I have a lower-end unit and it was not really designed for the brutal winter.

I was going to get a few bottles of that spray-in expanding foam stuff to seal the ceiling holes that are condensating. I was also thinking about drilling a hole or two in the closet wall where the insulation is lacking and spraying some of it in there, too. My fear is that it will expand too much and split something. Also, it'd be harder to hide the holes in the shower.

Anyone have any suggestions? Do you think the spray-in solution would work for the walls?

 

[howdymi]

We leave a roof vent just slightly open and there is no moisture problem.  In the bathroom we do the same with the roof vent when we take a shower and leave it open just a crack all the time.

 

[John Canfield]

One of my technical contacts at Winnebago says that your Adventurer and my Horizon (for one example) are ".. built, structurally, the same as yours (talking about my Horizon), the same 'R' factors are involved.."

His recommendations to help mitigate the condensation problems are:

"...they could help themselves by not closing off the bedroom at night, by closing this off, they trap the heat and moisture given off by their bodies and  respiration into a small space.  This will exaggerate any potential condensation issue.  I think that if they keep things opened up, including the closet doors at least partially open and move the dehumidifier closer to the center of the coach, they will see better management of their moisture issue.  I have seen owners have condensation in slideout overheads for example, be able to get rid of the issue by leaving the overhead doors open and have a fan or dehumidifier running on low.  (just an example)...."

 

[TheNextBillGates]

Thanks for reaching out, John. Here's a few more details:

Regarding the shower, the vent is with the toilet behind a separate door. I can try your suggestion, but I am already turning on the basement fan which seems to create plenty of circulation which the dehumidifier can then take care of. We don't even have moisture on the mirrors. It's just that section of the wall. You can touch the area and feel that it is very cold...then slide your fingers down the wall and feel it warm up significantly. This is why I feel there must be a missing piece of insulation.

The same goes with the closet. I can put my hand on the top corner and it's very cold. If I slide my hand down the wall I can feel a dramatic difference where (in my opinion) the insulation starts. Within the closet, there's a couple screws going into the wall. They are all dry except for the one that screws into the area that is colder. That screw is wet.

The reason we keep the door shut is that we are using up LP like crazy. By closing the door and letting the electric heater keep us warm at night, we can dramatically lower the coach thermostat. LP is 3.45 a gallon and I'm taking three smaller tanks up the street once a week. We're burning well over $200/month in LP, and that's by turning it down to 47 - 50 at night. I'd also have to rig the lights in the closet if I'm going to leave the doors open because the lights come on when you open the door.

 

[Kim (skyking4ar2) Bertram]

I am not sure where you are, but we also are 38' with two furnaces and we are not burning near that kind of LP. We have been in the cold since Oct (teens in Taos, twenties in LA and now AL), and have never burned more than 15 gals a month.

We use the sun to heat the coach in the day (furnaces never come on), thermostats at 58 at night, with an electric radiator, and electric mattress pad. We can hold 58 degrees until the sun comes up easy, then hit 80 without strain.

Could you have a massive heat loss somewhere? thought about using a laser thermometer to look inside and out for heat drains? We have found several pneumonia holes, including the air vents on the dash (!) and plug 'em when we find 'em.

 

[TheNextBillGates]

I'm in central VA at the moment. Nights have been upper mid teens to upper 20's. Days have been mid to upper 30's. Probably the biggest guzzler is in the AM. I actually set my alarm twice - once to wake up and turn the heat on and another to actually get up. It takes 1.5 - 2 hours to get the entire coach from 47/50 to 71 degrees. We only have a single furnace. Like you, the sun keeps us warm for most of the day. The furnace does come on maybe every 30 minutes but only runs for 5 - 10 minutes. At night though, it can work quite a bit to keep everything warm. That's why we lock ourselves in the bedroom!

Great idea about the laser thermometer. I'll get one and report my findings.

 

[JPete]

Another idea would be to get some 1 or 1.5 inch thick foam board from Home Depot and cut strips on insulation a little larger than the areas that are cold and use some velcro to hold them in place. You could take them down when the weather warms up and they are unnecessary. You could cover the foam with fabric or such to decorate if it is exposed.

Spray foam is available in a low rise form from Great Stuff. I believe HD sells it as well for use around windows and doors.

Just an idea.

Pete

 

[Kim (skyking4ar2) Bertram]

I think the hard cold days are killing you. We have not had more than two days cold in a row, and it was in the forties. Makes a difference!

Head south! Might get you another ten degrees!!

 

[afchap]

I'm a little upset that the coach isn't a sealed up a bit better. But, I suppose I have a lower-end unit and it was not really designed for the brutal winter.

If it weren't "sealed up" as good as it is, you would have less condensation ...that is the moisture in the inside air from cooking, breathing, showering, etc. Maybe you meant "better insulated".  Very few if any RVs are designed for extended severe cold, though some do better than others. It WILL take either LP or diesel (depending on the coach systems) to keep things from freezing.  We have learned that when temps are in the 20's for more than one night we need to open overhead cabinet doors to allow some circulation that helps prevent condensation on the outside walls. We haven't done that in the closet as ours is cedar lined ...it may be sweating under the cedar where we cannot see it!!    We also use a small electric heater to help in using less LP when temps are above freezing but too low for the heat pump to function. Our coach has two LP furnaces. We keep the bedroom furnace set around 55 or so (rather imprecise thermostat on it), and the front in the low 60's at night.  Our fleece sheets and comfortor keep us toasty in the bed. During the daytime, it helps to be parked where the sun can hit the side of the coach so you get some solar help.

 

[TheNextBillGates]

You are correct about my word choice. It is actually "sealed up" well as you can hear a major different in the ceiling vents if they are running and you close all the windows/doors and then open one...the air moves very differently (indicating it's sealed quite well).

I've taken the laser thermometer around although it's not as cold tonight and variances aren't as drastic. What I have discovered is that the walls seem insulated ok - except at the top and the ends. The top 2" or so of the walls and the end 2" or so touching the rear cap of the coach read a dramatic (10 degrees or so) lower temperature. After removing things from the closet, it appears the condensation was a combination of the top 2" and the far right 2" that were much colder. In the shower, the 1" or so is at the top of the coach, so the steamy water in conjunction with the very cold portion of the wall near the ceiling causes condensation to build up almost instantly during a shower.

For the closet, I purchased one of those disposable moisture removing buckets. Damp-Rid competitor of some sort. So far it's dry in there but it's also been warmer the last few days. We'll see how well it works. I'll keep drying the wall in the shower for now. Running the vents after our showers seems to dissipate the moisture in the bathroom very quickly.

Any ideas why the corners are colder? I guess it has to do with the structure. Does the insulation stop at some sort of aluminum frame? The uninsulated aluminum frame may be what's colder...

 

[afchap]

Any ideas why the corners are colder? I guess it has to do with the structure. Does the insulation stop at some sort of aluminum frame? The uninsulated aluminum frame may be what's colder...

  Exactly the case. Click on the attached pic below for a good look at the roof/wall joint cross-section.  The "foam plug" portions are inside aluminum frame pieces.

 

[David and Derita]

Here is what we did to reduce condensation and heat loss. We bought 2 dehumidifiers; a larger one for the main area of the motor home and a small one for the bedroom. When it is really cold we open the closet doors and the overhead closet doors just a bit. We went to Home Depot and bought the 1/2 inch rigid air conditioning duct insulation (it comes in a 4' x 8' sheet) and cut it to size and installed it in the closet and overhead closet in the bedroom, in the overhead bins located in the main living area and over the driver and passenger seats.

In cold and hot weather we used to have large amounts of condensation on the inside of the windshield and windows. After adding the dehumidifiers and the extra insulation we rarely have any condensation at all.

 

[TheNextBillGates]

I guess even though the frame has a foam plug, the cold is being transferred right through the metal. Thanks for that pic.

D&D, is your smaller dehumidifier one of those ones without a compressor? Does it work for you? I've seen mixed reviews. Our larger one with the compressor (really the smaller of the compressor models - 35 pint) works fine but there's no way it's getting in the bedroom.

 

[Jim Godward]

One of the things we learned in keeping condensation down in cold weather is to try and keep at least one vent open about 1/4".  This seems to help move air through and exhausts warm moist air.  we turn the furnace down to about 60? or a little less and use electric blanket to keep us warm at night.  We have in the past used a 12/120 volt mattress pad when we had the other MH.  We used the 12 volt feature when boon docking and 120 when hooked up.  That worked well.

When we got the DSDP, we used the inverter for night heating when boon docking but then the manufacturers changed the controller for the blankets/mattress pads and the modified sine wave inverter power destroys the controllers so we now just don't turn the heat quite so low and add blankets.

Just our experience here in MT and in traveling to the south west in December and January.

Experiencing a warm January in MT this year, highs in the 40s and lows in the high teens and 20s!!   

 

[afchap]

We went to Home Depot and bought the 1/2 inch rigid air conditioning duct insulation (it comes in a 4' x 8' sheet) and cut it to size and installed it in the closet and overhead closet in the bedroom, in the overhead bins located in the main living area and over the driver and passenger seats. In cold and hot weather we used to have large amounts of condensation on the inside of the windshield and windows. After adding the dehumidifiers and the extra insulation we rarely have any condensation at all.

  If you are SURE there is no condensation happening behind the insulation, your solution is working great.  Have you checked to be sure the insulation is not getting wet/absorbing moisture against the walls?  It may be that the de-humidifier is keepi9ng that from happening.

 

[David and Derita]

D&D, is your smaller dehumidifier one of those ones without a compressor? Does it work for you? I've seen mixed reviews. Our larger one with the compressor (really the smaller of the compressor models - 35 pint) works fine but there's no way it's getting in the bedroom.

Yes, the smaller dehumidifier is an EvaDry electric petite dehumidifier that uses Peltier technology instead of a compressor and it works very well in the smaller bedroom area. The larger unit is a SoleusAir 40-E. Unlike other large units that we looked at, the SoleusAir doesn't exhaust really hot air. Together they keep the relative humidity between 38-48 percent. We got both through Amazon.com

 

[Retired CSIGuy]

Go to Eva-Dry's web site.  They have a wide array of dehumidifiers of all sizes.  We have two of the small (1 pint) units for my 39ft 5ver  work great.

 

[Wagonmaster2]

Hey guys,

Well, I'm stuck in the cold for a while...I have my external LP tank hooked up and we're managing to stay rather toasty! My 38J has a rear bedroom we can close the door and a small electric heater keeps us toasty at night while the coach thermostat stays at 50. During the day I crank it up to 70. If we're lucky, it gets warm enough to use the heat pump.

My issue is with condensation. As most have seen at some point, we saw moisture on the windshield and window frames. I bought a dehumidifier and sat it in the front of the coach and it has all but eliminated the excess moisture. However, certain areas of the coach are still problematic:

- In the shower, there's about 1" of wall that I can see between the top of the shower and the roof. It is VERY cold (lack of insulation I suppose) and condensates heavily during a shower.
- The closet is located on the passenger side rear corner. The top right corner (top rear corner of the coach) is VERY cold and condensates as well. This is a section at least 6" tall and 2' wide. This causes our clothes to get wet.
- The lights in the closet come through the ceiling. Condensation drips from these holes & wires and short out the closet lights. This is not a leak from the exterior, only condensation and only during the winter.
- The bottom corners of our slides are very chilly. Since Winnebago used a lot of fake wood with wood grain contact paper on it, we're getting several areas where the wood grain is peeling off due to the moisture.

In the end, I'm a little upset that the coach isn't a sealed up a bit better. But, I suppose I have a lower-end unit and it was not really designed for the brutal winter.

I was going to get a few bottles of that spray-in expanding foam stuff to seal the ceiling holes that are condensating. I was also thinking about drilling a hole or two in the closet wall where the insulation is lacking and spraying some of it in there, too. My fear is that it will expand too much and split something. Also, it'd be harder to hide the holes in the shower.

Anyone have any suggestions? Do you think the spray-in solution would work for the walls?

We had the same problem with condensation at the top of the shower wall just below the ceiling until we started running the dehumidifier at night in the bathroom area, don't need  to every night though.  We have a humidity gauge and just move the dehumidifier around wherever its is needed the most and have been able to keep the condensation off  the windows and wall just fine.

Allen