Moisture under queen mattress after overnightingproblemma

[Helli M]

Hi,
The underside of our queen mattress in main sleeping berth is damp after sleeping overnight. The board over water tank which is below the mattress is very damp on top. I have mattress cover and bottom sheet on top of mattress and hatch and port windows are open overnight too. Doesn't anyone have the same problem? Is there a solution? Thanks !

 

[jssailem]

Look at the "HyperVent Mattress Pad"
I had a similar issue. This resolved it on my boat.

 

[sesmith]

Froli sleep system works for us.

 

[NYSail]

Second hypervent. Had same problem on old boat...:. Immediate cure!

 

[Spindrift NH]

Froli works for us as well

 

[Ralph Johnstone]

The underside of our queen mattress in main sleeping berth is damp after sleeping overnight.

Your mattress behaves exactly the same as an exterior house wall when it comes to condensation. Correct the cause, not the results. See #4.

https://forums.sailboatowners.com/index.php?threads/condensation.152384/&highlight=condensation

 

[thinwater]

The other solution (more effective than ventilation in cold climates) is insulation. The condensate only forms because the fiberglass is cold. Thus, a ~ 1/2-inch pad of closed cell foam under the mattress generally works. In my case, the fiberglass under the mattress is cored (insulated) and thus I have never had condensation.

 

[jssailem]

Thin water, I am guessing you have never been in a boat, at night, with the temps in the mid 50's, the moons out and there's heavy breathing to steam the windows. That's when I see condensation.

 

[justsomeguy]

I'd like to commend all the respondents to @Helli M 's question for not "going there".

If you're following my stream of thought, I am relieved.

 

[Helli M]

Thanks all - we've had a few boats but never this problem under the mattress. Will adopt some of your suggestions - thanks

 

[Ralph Johnstone]

If you're following my stream of thought, I am relieved.

YOU'RE RELIEVED ? ? ?

How do you think Helli M felt ?

 

[Head Sail]

Other advise is good but I'd close the hatch and the port windows at night. Cool moist air in the evening is being drawn into the warmer cabin. Warm air acts like a sponge to the cool moist air. When the temperature in the cabin begins to cool, the moisture is wrung out and will collect on everything. Like when you poke your head out in the morning and everything is soaked.
Make sure your CO monitor is working too.

 

[thinwater]

Thin water, I am guessing you have never been in a boat, at night, with the temps in the mid 50's, the moons out and there's heavy breathing to steam the windows. That's when I see condensation.

You would be guessing wrong. I'm not that old.

 

[ravenbob]

Warm humid sleeping air under the blanket is the problem. The blanket keeps the warm air trapped against our skin. That's its job. So where does the humidity and air actually go? Down into the mattress. And, if the mattress is resting on the cold fiberglass, it condenses into water and BANG. The cabin starts smelling like a dank mildewy basement.

We had exactly the same problem. We use Den-Dry. It lifts our mattress about three quarters of an inch above the fiberglass, and lets the air move freely, carrying the humidity away before it can condense, and what little does condense on the fiberglass evaporates easily, because it's not soaking into the mattress. Once we put that under the mattress, the problem went away entirely.

 

[NYSail]

HyperVent is the greatest product. Inexpensive and it works. We use the stuff not only under the mattress but in any storage area that is susceptible to dampness. Not expensive either

 

[ravenbob]

Yeah. We do the same thing with the Den-Dry, but the mattress underlay is a bit stiff to conform to the curves of the hull... There's a locker-liner that's a little thinner and way more flexible. Den-Dry is a buck cheaper per foot than Hypervent. For the locker liner, three bucks per foot less expensive.