Condensation under bed??

[TinTin]

I think you could insulate under the bed (i.e. beneath the wood) if you put a vapour barrier above the wood to keep humidity away from the wood. Insulating beneath the wood without an upper vapour barrier might cause more problems than it solves.

[Protagonist]

Dumb question, but why not coat the plywood with Thompson's Water Seal to keep it from absorbing moisture? That way the plywood itself becomes a vapor barrier.

[Cannonball]

I asked that same question in a different thread on this subject. One reply was that they would be concerned about using a chemical product like that in an enclosed space, and that close to your person. Made sense to me. Whenever I have used Thomson's on a deck, it was pretty stinky. I am going with your Reflectix plan. Have it down, and will get to try it out this coming weekend.

[dkottum]

I have used Thompsons Water Seal, but never would indoors.

[chaseav]

Nooooo... that's outdoor use only and even then it needs a stiff breeze during application. Been using it for years on concrete and decks. It would only repel the moisture and cause it to build up on the outside of the wood which doesn't solve the problem. I'd rather replace the wood every few years. Foam core is the solution I think. Probably on the door, semi-permanent for winter use.

[TG Twinkie]

The moisture under the mattress is not from the outside unless you have a leak.
Condensation from the inside moisture is the cause. The plywood is cold and the moisture condenses on it just like when the windows in your TV fog up.
Adding to the problem. The moisture is absorbed into the mattress. Plus the mattress acts as an insulator from the warm space.
Heating the space below the plywood is one answer. It does not have to be as warm as the cabin temp. Just enough to where the dew point is not reached.
Another solution might be to raise the mattress off of the plywood. What comes to mind is the teak slats used in shower stalls to keep your feet off of the floor.
The idea is; they are slats that would allow air to flow under the matters. Any material that will not absorb moisture and create a sort of grate under the mattress may work. Something that would not rust.
Just thinking out loud.


Sent from my iPod touch using Airstream Forums

[Florida 55]

There is a product specifically designed to eliminate the problem of moisture condensation under cushions. It is a spacer fabric that provides both lift and air circulation. Spacer fabrics are used for marine, automotive, and other applications. There are several sources for spacer fabrics you can find on the Internet. Here is a link to one resource; www.hyperventmarine.com

I have no personal experience with the vendor listed above so I cannot attest to the quality or suitability of the product. I have direct access to a US textile mill producing these fabrics but I am unable to obtain product for resale as my client will not sell directly to the public.

My knowledge of these products comes from years of work in the textile industry. If you have air cooled seats in your automobile or truck there is likely a spacer fabric directly under the leather or vinyl seat cover. Air does not circulate easily through the dense foam used in vehicle seats. The layer of spacer fabric over foam allows cool air to circulate from an air blower to the holes in your seat cover. The foam under the spacer compresses to provide cushioning while the spacer fabric lifts the seat cover above the foam allowing air to move.

Some high tech running shoes also employ spacer fabrics. Athletic shoes have both moisture management and compression requirements. Spacers are also employed instead of foam in some high end brassiere molded cups. No further comments but you ladies understand the issues.

Spacer fabrics can be purchased in various thicknesses. The amount of compression the fabric allows can be varied as can the density of the fabric. Some spacers actually employ moisture wicking fibers.

An inch to two inch thick roll of spacer fabric, with a fairly open construction and limited compression should be perfect for air circulation under an RV mattress, using a synthetic fiber such as polyester. The right spacer fabric will hold your mattress above the plywood, allow air to circulate under the mattress, and prevent condensation from being trapped.

I suggest doing an Internet search for suppliers, do some reading, and then call suppliers to talk about the application. Some of them may be willing to send you a small sample before you make a purchase.

There are only a few textile mills remaining in the US capable of producing these specialized fabrics. While I know what it costs to produce the fabric, I don't know the markup structure between the mill, the retailer, and the consumer. I'm guessing a spacer with enough loft and sized for a queen mattress would cost a consumer between $60 and $100, but this is pure speculation.

If anyone has questions, post on this thread or send me a PM.


Sent from my iPad using Airstream Forums

[Rocinante]

Camped this week with our Reflectix and Hypervent sandwich. External temps were in the low 40's at night with an internal temp of 63. Not a particularly tough test, but no moisture formed on the Reflectix, though we did get some condensation on the windows. A good start.

[r carl]

Originally Posted by Protagonist

Dumb question, but why not coat the plywood with Thompson's Water Seal to keep it from absorbing moisture? That way the plywood itself becomes a vapor barrier.

How about linseed oil, wood oil, or varnish?

[switz]

Since the Classic solid Hickory cabinets are sealed with a clear finish, I would think the same finished applied to the plywood might help and be safe.

[TG Twinkie]

Condensation forms on a cold surface. Since the cabinets are in the warm space the condensate does not form.
Preventing the interior surface of the board under the mattress from getting cold is the answer. Air circulation will also prevent condensation build up.
Insulating the space under the bed and providing warm air flow will also help.


Sent from my iPod touch using Airstream Forums

[grizbear]

The best answer for us was to reduce the humidity in the air we use a dehumidifier and also use a pouch of damp rid under the bed everything stays very dry inside the entire camper. Best of luck Rand

[cwf]

hmmm. how about a 'mattress pad heater' under the mattress?

[switz]

Then the moisture from sweat is on top the mattress?

[dkottum]

Equalizing air temperature under the bed to interior air temperature is a solution, vapor barriers and insulating pads are pretty much Band-aids. A fan circulating air into the area, or opening the area enough to allow natural equalization of air temperatures, along with ensuring exterior door seals are tight, ought to eliminate the dew point condition that is causing the moisture to form.

[Rocinante]

After traveling roughly 8,000 miles in 8 weeks with Rocinante and camping in temperatures as low as the mid-20's (F) with snow outside and plenty of condensation on the windows, we can happily report that our bed sandwich of a layer of Reflectix under a layer of Hypervent under the mattress successfully prevented condensation under there. Our experiment was a success in these temperature ranges.