mattress moisture barrier

I used to use a sheet of 3/4" Styrofoam board way back in the ~60's and early 70's under the mattress in our TC's. Then went to closed cell foamboard until the early 90's. That's when we changed to 2 layers of Astro-Foil (the better stuff than Reflectix) and it was even better for eliminating moisture and/or any mildew at all as we'd use one of our TC's in both Summer in the northern USA and Canada and Winter even below zero in the same areas. Warmer too!

The foamboard was OK but not nearly as good as the Astro-Foil and is why we still use the same 2 layers yet today. It just doesn't wear out or crumble either and doesn't squash in pressure pushed areas like the foamboard did. An added good thing is that the 2 layers raise the mattress less than the foamboard did and make opening the cabinet doors easier.

For the last roughly 15 years we have had the same Aerobed air mattress in the TC's owned with it's inside the mattress blow up pump with the wired remote control. Only a simple inverter is needed for the 110 AC pump motor without hookups to function anytime anywhere. It's so much more comfortable for sleeping than a conventional mattress, much warmer in Winter and cooler in Summer and so easy to adjust air pressure up or down as desired with the press of a button. Sleeping on air warms up to body heat or an electric heated mattress top so much faster than any other type of mattress type. 15 to 20 minutes tops from freezing to 70. It's perfection+.

Love it so much that our 5th wheel has the very same system and so did our class A's as we had learned what really works anytime anywhere.

HyperVent was designed expressly for controlling moisture under seat cushions, mattress, etc.. Is it expensive, yes, but you own an expensive RV carried by an expensive truck and that didn’t stop you.:R

Something to allow an air break under the mattress is a good idea but it does not allow air flow. There is no reason for the air to move so in the middle of the mattress the air does not circulate no matter what you have the mattress sitting on. It will add an air break to the mattress not touching the camper but that is all.

More importantly you should leave your heavy sheet (s) / blankets rolled back on the bed in the morning and open a window or a vent to change the air in the cab over. Especially the air in the corners of the cab over as it is stale and moist and this is more likely to cause issues with the mattress touching the walls and getting mold than anything. A small 12v fan running during the day blowing air that way will help as well.

I have thought to use a foundation dimple type moisture barrier, fabric side up to prevent moisture under the mattress. We have not experienced moisture under the mattress yet though as it is a cheap stuffed spring type that has lots of air moving through it. No collection of moisture seems to occur.
This is one type of the dimple sheet.
Another alternative I've thought to use is a section of cedar lattice fencing. Two of them lain over each other under the mattress would provide larger venting channels. Quick cheap and easy...

Optimistic Paranoid wrote:
There are three methods of heat transfer. Convection, conduction, and radiation. Reflectix has NO insulation value as far a convection or conduction goes. It reflects radiation - AND IT NEEDS AN AIR GAP in order to do THAT.

My My. This reminds me of the blind men feeling an elephant. All are correct, as far as they know.

The above is mostly true. Reflectix has a marginal R value of 1.1 for conduction.

The original question was about moisture in the mattress. Moisture is generated by the body and will migrate down through the mattress material (except some foam mattresses, toppers and air mattresses). If the mattress is cold, the moisture will condense where the dewpoint temperature is encountered. Condensed moisture in or under the mattress will promote mold growth.

One solution presented here is to ventilate the underside of the mattress to allow air flow. This air gap stops conduction, can help remove moisture and insulates slightly.

Another solution is to use a foam topper to prevent migration of moisture down through the mattress. Some of us sweat when sleeping directly on a foam topper because moisture cannot penetrate.

A third solution here is to insulate under the mattress to keep the mattress above the dewpoint temperature. The moisture will migrate out after you get out of bed (assuming it is not too humid in your TC). A sheet of foam is probably best for this solution.

Another solution is to use a heating pad to elevate the temperature of the mattress above the dewpoint temperature.

All solutions work in some situations, but not all work for all situations.

Putting reflectix under a mattress provides marginal insulation, but in some cases, might be enough. Unless one reflective surface "sees" air, it will not function as a radiant barrier, only as a marginal conductive barrier. The air inside the mattress does not count.

Hope this helps,

(I needed a break from writing Christmas cards ;))

I actually called Reflectix and described what I wanted to do, to make sure it was correct, and they said Yes, that's exactly what it's intended to do.

Optimistic Paranoid wrote:

jimh425 wrote:
Are you saying there is no air in your mattress or beside your mattress? It must be hard. ;)

Go to Reflectix's own web site and check their Frequently Asked Questions. You will see that they say that an air space is NECESSARY for it to work as reflective insulation, and if it's IN CONTACT with something, it will act an a heat conductor.

Again, your bed doesn’t have air in it?

Or, go see this thread. https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29799017.cfm

Never had a moisture problem in even the coldest weather because we have a Froli system under our mattress. Sleeps warmer in winter and cooler in summer. Works well for us.

jimh425 wrote:
Are you saying there is no air in your mattress or beside your mattress? It must be hard. ;)

Go to Reflectix's own web site and check their Frequently Asked Questions. You will see that they say that an air space is NECESSARY for it to work as reflective insulation, and if it's IN CONTACT with something, it will act an a heat conductor.

Optimistic Paranoid wrote:
Reflectix has NO insulation value as far a convection or conduction goes. It reflects radiation - AND IT NEEDS AN AIR GAP in order to do THAT.

Are you saying there is no air in your mattress or beside your mattress? It must be hard. ;)