Bed platform moisture

[llanderson64]

We are traveling in the Pacific Northwest for the first time in our new (to us) 2011 23FB trailer. We noticed the other day that the plywood platform under the mattress was very damp! I believe the problem stems from cold air in the exterior compartment right under the head of the bed coming in contact with the warm interior air. Seems like a design flaw on Airstream's part....We propped up the mattress and were able to get it to dry out, but we need a better permanent solution so mold does not grow in the future. Anyone else run into this and solve it?

[SteveSueMac]

I never get good results searching here, but searching in Google returned this thread in the forums:

http://www.airforums.com/forums/f458...lem-85283.html

Good luck!

[dkottum]

Not an unusual complaint but we have never had it in some 30 months total sleeping in our Airstream, so I wonder why some have it and some don't.

For some reason the moist interior air reaches it's dew point at that location. One thing I noticed early was the exterior hatch to the under bed storage was not closing tight against its seal. That would allow cold air to enter the area under the bed and contribute to the problem.

You can check that seal easily by turning on the storage compartment light after dark, then see if the light is visible around the exterior of the hatch when closed. I took off the latch arm and bent it slightly so it would pull the door tighter.

Another solution may be to create an opening to that storage area from the inside so warm air can enter and minimize the temperature differential causing the dew point to occur there.

And of course ventilating the trailer with cracked windows or vents will ensure excess breathing, cooking and bathing moisture will not build up.

[Ted S.]

This is a common problem in the RV and Marine world, although it's been better adressed with boat owners.

The condition is a warm moist environment (bed with two bodies) in contact with a cold surface. This result is condensation because the second law of thermodynamics says moisture goes from warm to cold.

There are several products on the market that promote air circulation:

Dry-Mat_Anti_Condensation_Layer

DRI DEK Dri-Dek Panels | West Marine

The alternative solution is insulation as in the above post, I would opt for the foil faced polyiso as in the link as it provides a good vapor barrier.

[dznf0g]

A dehumidifier helps as well as a 200 watt personal electric heater in the under bed storage compartment. (On shore power, of course)

[ghaynes755]

The stuff from Hypervent (HyperVent Marine - Putting An End To Condensation) is what I would use.

[AnnArborBob]

On our 2014 Eddie Bauer, there are two openings on the vertical portions of the bed platform on each side of the bed to allow easy access to tubs for storage. Those openings seem to be sufficient to allow air circulation under the bed so that you don't get as dramatic a temperature differential between the under bed area and the cabin of the Airstream. You might try making some similar openings. If you didn't want to make them as big as ours (to accommodate the storage tubs) I'm sure that smaller openings would work as well.

[SteveSueMac]

AnnArborBob - did you have doors there that you removed?

Ours (27FB Flying Cloud) just has them as openings under the bed. We've never had the condensation problem and have had nights where it was in the 30s outside and toasty inside as well as hot summer days outside and cool temps with AC inside.

[A W Warn]

I did three things that helped with moisture under the mattresses in both of my trailers:

1. I have esophageal reflux, so I needed to elevate the head of the bed in both trailers. I cut long wedges out of a 2 x 4, about 3' long. I attached these equally spaced at the head end of the bed on top of the original bed platform, then cover the wedges with another layer of plywood. The air space between the wedges allows air to circulate under the mattresses.
2. In the Safari (corner bed) I cut a 4" x 10" opening through the side of the bed frame then installed a louvered cover, which allows air to circulate into the storage space under the bed.
3. Where the original seal was not contacting the entire perimeter, I installed a new storage hatch seal from ODM on the rear hatch on the Safari.

[AnnArborBob]

Originally Posted by SteveSueMac

AnnArborBob - did you have doors there that you removed?

Ours (27FB Flying Cloud) just has them as openings under the bed. We've never had the condensation problem and have had nights where it was in the 30s outside and toasty inside as well as hot summer days outside and cool temps with AC inside.

We never had any doors there. I am assuming that the openings serve the dual purpose of providing access to the storage tubs and providing air circulation under the bed to avoid the moisture problem mentioned by the OP.

If someone didn't have these, if would be a piece of cake to cut some openings in the plywood base and install some vent grates if desired just as Alan above did. I would think that two openings about the size of a typical floor air vent in a house would be sufficient.

[Landrum]

All you need to do is buy a roll of Reflectix insulation at HD or Lowes and staple to the plywood under your mattress.


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[bunni]

Originally Posted by Landrum

All you need to do is buy a roll of Reflectix insulation at HD or Lowes and staple to the plywood under your mattress.

Which side of the plywood? The top next to the mattress or the bottom facing the storage compartment?

[Bruce B]

No problems in our Airstream but we use the Hypervent product on our boat. Problem solved!
Bruce

[Landrum]

On the top.....between the mattress and the plywood. This solved the issue when it happened on our 23fb. As soon as we got our 25fb I added the insulation and we haven't had any moisture issues.


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[Rocinante]

We went all in. We have a layer of Reflectix carpet-taped to the plywood under the bed. Then we threw down an old flannel sheet. Next, we put a layer of Hypervent. Then, the mattress. (The flannel sheet protects the Reflectix from the Hypervent, which can be a bit pokey.) If that's not enough, we'll add a second layer of Reflectix to the first. As a side benefit, the bed is also more comfortable.

[Protagonist]

Originally Posted by Ted S.

There are several products on the market that promote air circulation:

Dry-Mat_Anti_Condensation_Layer

Dry-mat laid directly on the plywood, with a Mylar space blanket on top of it— under the mattress— to reflect your body heat back up through the mattress. Side benefit, you'll sleep warmer, too.

[HeavyAssault]

So is this a matter of the outside air and inside air, leaking seals, or the human body heat transfer? Looking at the HYPERVENT product one would say it's just body heat transfer causing the issue.

[Protagonist]

Originally Posted by HeavyAssault

Looking at the HYPERVENT product one would say it's just body heat transfer causing the issue.

Not really. Condensation happens when warm moist air at a temperature above the dew point comes into contact with a surface whose temperature is below the dew point, and stays in contact long enough for the moisture to condense out of the air.

So control of condensation can take many forms:
* Keeping surfaces warmer than the dew point, which is difficult when the surface has cold air on one side and warm air on the other;
* Keeping air circulating so that moisture doesn't have time to condense out of the air onto the cold surface;
* Keeping the air drier by raising the air temperature;
* Keeping the air drier by lowering the moisture content.

But it is true that Hypervent material is designed to only address one cause of condensation, namely the lack of circulation. Whether that will be enough to do the job for you is something only you can tell, and only by trial and error.

[A W Warn]

Originally Posted by HeavyAssault

So is this a matter of the outside air and inside air, leaking seals, or the human body heat transfer? Looking at the HYPERVENT product one would say it's just body heat transfer causing the issue.

Another way to understand what is happening:
When you listen to a weather report they sometimes give a temperature called the "dew point", the temperature at which moisture will condensate out of the air. That temperature will usually fall between the outside unconditioned temperature and the inside conditioned (heated or cooled) temperature. When that "dew point" temperature occurs within a confined space, where the relative humidity is high enough, the "dew" makes the interior of that space wet. That is what is happening within the mattress. A sweating body can contribute additional moisture and heat.

Insulating beneath the mattress may move the location of the dew point to a point outside of the mattress.
Or providing air circulation beneath the mattress may allow the dew to evaporate as it forms, and also may move the dew point outside of the mattress.