Condensation and Roof Construction Concerns

pianotuna wrote:
Hi klawklr,

Cracking a window. The idea is that hot moist air rises drawing in cool air. As the cool air warms it drops the relative humidity inside the RV. I would relocate the electric heater to where the air is coming in. You can experiment with the size of the openings needed. Make a crude draft gauge from a piece of Kleenex. Use the roof vent to control the amount of air flow while measuring the draft at the window.

I am full timing in a class C. Right now the temperature is -7 C (19 f) and the low is forecast to be -10 C (14 f)

I've used my RV at -37 C (-34 f) and have boondocked for 5 days where the high was -27 C (-16.6f)

klawklr650 wrote:

pianotuna wrote:
Hi,

Crack a roof vent and open the window (a bit) that is farthest from it. Place one of the electric heaters near the window.

Condensation is about keeping the surfaces above the dew point temperature. I have been known to run a humidifier inside my class C in winter time, but I live in the North American equivalent of Siberia.

Thanks Don, I have opened the bathroom vent about 1.5 inches. Are you suggesting cracking a window farthest from that vent? Or cracking a roof vent, say, in the living area and cracking a window in the bedroom which would be farthest from the roof vent? I would suppose then I should relocate an elec heater to the bedroom where the window is cracked? Are you using your class C in winter time?

Pianotuna, thanks for the picture you've drawn for me. I can now visualize what you and others have discussed. I'll start experimenting with vent and window adjustments. I have to say, the temps you are in are no where near where we are. Our lowest this season has been 26. I cannot even imagine the temps you have been in with the level of insulation this unit is constructed with.

klawklr650 wrote:

NC Hauler wrote:
last 3 to 4 day's, including right now have been in the 20's and low teens with wind chill around 10 degrees....furnace running, several ceramic heaters going at various times, all 4 vents have the insulated "pillow" in their opening in the roof....I opened one when taking a shower...have had zero issues with condensation anywhere in our 5th wheel, do run the exhaust fan when using the range and fan automatically vents when using the convection oven....It's 28 degrees right now, with a 23 degree reading with a slight breeze and about 2" of snow on the ground now, but the sun has finally broken through after several day's of really bad weather...

Happy Thanksgiving to all:)

NC Hauler, so you are doing something slightly different. You are NOT venting unless using the shower, range or convection oven. My furnace would probably be running almost all the time. Are you in a four-seasons built rig?

HR considered it a 4 season rv, though I really don't think it is. It does have dual pane windows and when the furnace is running, the basement is heated to some extent as is some of the floor and all of the tanks are heated....It's 18 degrees right now with a wind chill of 16....warmer than yesterday morning...Have had no frozen water, though I do let it "slightly" dribble" in the kitchen sink when temps drop into 20's...The "highs" over the last 3 day's only got up to 34. The furnace has run quite a bit, I do have two ceramic heaters, with thermostat settings that help take the 10 degree chill out of the air and colder when winds were whipping to 25 mph...also have an electric fireplace in living room to also help keep warm....zero precipitation on any window..

I have 4 vent's, two of them are the fantasta fan, one is a vent in the bathroom and another a vent close to the shower..When the wife or I have taken a shower, we remove the "insulated" pillow like square that fits into the opening perfectly, then when we're done, I seal the vent back up....so yes, all four of my vents, to help keep heat in, are closed...When wife is cooking, and yesterday it was pies and a turkey, the stove exhaust fan was going as was the fan in the convection oven....

To be 7 years old, the 5er has held up well and does a very good job of keeping us quite warm and cozy in temps into single digits and keeps us cool in up to 100 degree weather....

Do you have a recommendation on a dehumidifier? Brand, type, size?

This was in '98 and I sure don't remember the brand but both were bought at Lowes.

So, the lexan didn't help but did make things feel more comfortable? I've read about some using the foil backed bubble insulation mat'l. Was the lexan a different way to accomplish the same thing?

Yeah we have lots of wind out here on the plains and with temps down to zero or single digits the Lexan with foam backing acting as a air tight gasket really stopped drafts and cold radiating from just a single window pane. At first we thought about the bubble wrap but the wife wanted to be able to see outside.
She also made some cheap heavy curtains just for winter use. That 5er is gone and our current trailer doesn't have all those windows.

Living in a RV one winter changed the wife perspective of having lots of large windows.

RWjSIM2003 wrote:
I always run the fantastic fan with fan on lowest setting and vent open 1"-2" when camping in cold weather. No condensation even with heater and fireplace on.

RW, I've always considered a fantastic fan would be a good upgrade. Did you always have it or was it an added later? Do you remember if you had any condensation prior to the fan?

NC Hauler wrote:
last 3 to 4 day's, including right now have been in the 20's and low teens with wind chill around 10 degrees....furnace running, several ceramic heaters going at various times, all 4 vents have the insulated "pillow" in their opening in the roof....I opened one when taking a shower...have had zero issues with condensation anywhere in our 5th wheel, do run the exhaust fan when using the range and fan automatically vents when using the convection oven....It's 28 degrees right now, with a 23 degree reading with a slight breeze and about 2" of snow on the ground now, but the sun has finally broken through after several day's of really bad weather...

Happy Thanksgiving to all:)

NC Hauler, so you are doing something slightly different. You are NOT venting unless using the shower, range or convection oven. My furnace would probably be running almost all the time. Are you in a four-seasons built rig?

Hi klawklr,

Cracking a window. The idea is that hot moist air rises drawing in cool air. As the cool air warms it drops the relative humidity inside the RV. I would relocate the electric heater to where the air is coming in. You can experiment with the size of the openings needed. Make a crude draft gauge from a piece of Kleenex. Use the roof vent to control the amount of air flow while measuring the draft at the window.

I am full timing in a class C. Right now the temperature is -7 C (19 f) and the low is forecast to be -10 C (14 f)

I've used my RV at -37 C (-34 f) and have boondocked for 5 days where the high was -27 C (-16.6f)

klawklr650 wrote:

pianotuna wrote:
Hi,

Crack a roof vent and open the window (a bit) that is farthest from it. Place one of the electric heaters near the window.

Condensation is about keeping the surfaces above the dew point temperature. I have been known to run a humidifier inside my class C in winter time, but I live in the North American equivalent of Siberia.

Thanks Don, I have opened the bathroom vent about 1.5 inches. Are you suggesting cracking a window farthest from that vent? Or cracking a roof vent, say, in the living area and cracking a window in the bedroom which would be farthest from the roof vent? I would suppose then I should relocate an elec heater to the bedroom where the window is cracked? Are you using your class C in winter time?

MTPockets1 wrote:
We're full time and no matter the outside temp, we always keep a roof vent open. Also, when showering and cooking, exhaust fans are on. We've never experienced any condensation in any weather or temps down to 28 degrees. Don't know about lower, but venting moisture out will eliminate problem.

MTPockets1, thanks. I see you have a four seasons setup. Dual pane windows and the Yeti package (which sounds like the four seasons insulation offering). An open roof vent has solved, rather prevented a condensation issue for you? I don't use the shower but we do cook on an electric cook top. But, we don't have exhaust fans over the stove. I've got some experimenting to do it seems.

JIMNLIN wrote:

JKrussow wrote:
Just living in your rig creates moisture in the air and cooking and showering increases it rapidly. Since getting a dehumidifier our moisture problem is gone. Since the unit produces heat while in use we only use it in the winter and it pulls about a gallon of water out of the air in a 24 hour period. We have a 499 sq ft 5th wheel.

X2.
We tried the crack the roof vent(s) and a window but all that did was create a cold drafty interior and the central heater running 22/7 and did nothing for moisture on the walls and windows.

We even tried the fans and a couple of ceramic heaters but it did nothing for the wall/windows sweat issue.

Bought a dehumidifier and was a big help.

Bought another and the two together cured our interior moisture problems.

This 30' unit with a super slide had the usual R7 walls roof and floor and too many windows (13). Adding mobilehome skirting and 1/8" Lexan inside all those windows didn't help with the moisture issue but sure made a warmer interior.

Jimnlin, thanks. Since this is a military campground I don't think they will let me skirt the FW, even though I am one of the Hosts. But, I have wondered if it would help with the overall warmth though. Do you have a recommendation on a dehumidifier? Brand, type, size? So, the lexan didn't help but did make things feel more comfortable? I've read about some using the foil backed bubble insulation mat'l. Was the lexan a different way to accomplish the same thing?

We use our electric fireplace as well as our baseboard heaters (1in liv rm. and 1 in bed rm.) The dual furnaces rarely get used except to warm up quickly first thing in the AM.

Our rig has a 2 speed attic fan that takes care of any excess condensation. It is on 24/7. In the summer it helps with cooling and in the fall/winter it prevents condensation.

That said, I would seriously consider a dehumidifier to eliminate condensation, as well as adequate ventilation. It can surely ruin a unit if left unchecked

shadoow wrote:
we have a fantastic fan over our kitchen area. I would push or pull the control knob on the fan to the 'manual' setting, crack open the cover about 1" or so and run the fan. We were getting condensation on the inside of our dining/living room windows and it fixed that.
You might want to move the heater from the bathroom to the bedroom also.

Shadoow, I've thought about the fantastic fan as an upgrade to our rig. I need to replace the vent over the kitchen anyway and that vent does not have a "doghouse" over it like my other two vents. I know Maxair makes vent covers as well as other manufacturers. Your suggestion about moving the heater, was that to keep the bedroom windows warmer to decrease the condensation?