RTT Condensation under the mattress

[EricGagne]

This morning, for the 2nd time in about a month, I noticed when closing my RTT that condensation had built up under the mattress. It was a little wet and when lifting it I could water on the tent's floor.

Last month the nights were cold, temperature went as low as 2 celcius.

This week-end the temperature was around 18 celcius but it was very humid outside and it rained non stop for 5 hours yesterday morning.

I bought the tent last winter and used it only 3 or 4 times, I didn't think of checking for humidity under the mattress until I saw it by fluke last month.

So I'm wondering, is it normal to have condensation under the mattress and if so, how can I stop/reduce it. There was no condensation on the walls or the poles.

 

[Martyn]

This morning, for the 2nd time in about a month, I noticed when closing my RTT that condensation had built up under the mattress. It was a little wet and when lifting it I could water on the tent's floor.

Last month the nights were cold, temperature went as low as 2 celcius.

This week-end the temperature was around 18 celcius but it was very humid outside and it rained non stop for 5 hours yesterday morning.

I bought the tent last winter and used it only 3 or 4 times, I didn't think of checking for humidity under the mattress until I saw it by fluke last month.

So I'm wondering, is it normal to have condensation under the mattress and if so, how can I stop/reduce it. There was no condensation on the walls or the poles.

What brand of tent do you have, and what material the base is made of. Does the base have a metal skin?

 

[HenryJ]

Very timely post. I noticed exactly the same thing on mine this morning. I left it half open to air dry before closing it all up.

Weather here was warm. Low 56 °F , high 93 °F , dew point 54 °F, avg humidity 50%. We had a couple small thunder showers last night. Only enough for a trace of precipitation. The air was heavy and moist this morning.

Ours is the large Campinglab. It is a metal skinned base.

The moisture was on the bottom side of the mattress and top side of the floor. Under side was dry, cover dry, everything else dry. Total amount was probably less than a cup beaded across the mattress mostly near the hinge point.

It may just have been the warm bodies above and the moist air below?

 

[EricGagne]

Mine is the smaller CampingLab and is also made of poly and just like HenryJ it was wet from the middle going inward on both sides. I doubt that the whole of it would have made even a cup.

It bothers me a little because I don't know how this would ever dry unless I pull out the mattress and leave it in the sun. I'm afraid the humidity could damage the floor in time and that the mattress will get smelly.

 

[Martyn]

I've never had a RTT with a metal base, and have never had water under the mattress of an RTT with a wooden base. But the thought of condensation with a metal base has crossed my mind.

Water vapor condenses on a surface that is colder that the air temperature, so you'd expect to see lots of dew on the outside, under surface of the tent base.

I don't quite understand why it would form under the mattress as it would need a volume of air to carry the water vapor under there.

As the mattress takes up that volume my only thought is that the air in the mattress itself contains the water vapor and it's condensing through both the temperature differential between the base and the air, and compression (the people on the mattress).

 

[EricGagne]

y mind.

Water vapor condenses on a surface that is colder that the air temperature, so you'd expect to see lots of dew on the outside, under surface of the tent base.

I thought of that too, it seems strange that the floor would be wet inside and dry outside. I can only guess that condensation formed during the night and that by the time I was ready to fold the tent this morning the wind and warmer temperatures had dried the outside.

I don't quite understand why it would form under the mattress as it would need a volume of air to carry the water vapor under there.


As the mattress takes up that volume my only thought is that the air in the mattress itself contains the water vapor and it's condensing through both the temperature differential between the base and the air, and compression (the people on the mattress).

That's interesting. When I open the tent the floor is not completely flat because the hanging part isn't heavy enough to push/pull it down. I assume that the canvas will stretch with time and that it's gonna open completely. I mounted my tent on a trailer and I sleep with my head on the trailer's side and my feet on the "floating" side. If the weight of my legs is not enough to push it down completely then there's gap in the middle and probably a small "air bubble" under the mattress right there because it's fully unfolded.

I think it's conceivable that condensation will simply run inside and get everything wet. Maybe I can fix this simply by sleeping the other way around..........although I find it safer to have my weight above the trailer.

 

[salsataco]

Check into this stuff http://www.hyperventmarine.com/

 

[Martyn]

Check into this stuff http://www.hyperventmarine.com/

Good link:

"Why Condensation?
Plain and simple, a differential between the inside and outside temperature can cause condensation. A favorite place for condensation is under mattresses, bunk pads and cushions. Ask any boater and they'll tell you stories of damage caused by condensation".

I understand that condensation is common under mattresses due to temperature differences. But why is it a favorite place? Is it because the mattress isn't breathable and it holds moisture in the foam?

"A Simple Solution -
HyperVent is a special material comprised of a white spun polymer woven into a large, open, 3/4" thick configuration that is bonded to a breathable white fabric layer. Stiff yet flexible, the texture of HyperVent is not felt through the thinnest of mattresses".

Why does Hypervent work? Does the large open internal structure and breathable fabric allow the vapor to escape? I presume you put a layer of Hypervent under the mattress.

 

[EricGagne]

Martyn I googled "mattress condensation" and the 3rd result was this:

http://www.autohomeus.com/accessories/underMattress.php

I suppose it's similar to the Hypervent product. Autohome says:

The lightweight mesh construction is compression resistant (1 ton/meter2 )

That explains how air can move under the mattress even with the weight of the persons on top. I wonder if it would fold/unfold easily though. I found it on a Canadian Marine online store but it's 100$ for a 39" x 72" piece. It would require 4 of them to cover the 55" x 94" area of my tent.....that's a lot of money to spend without knowing if I'll be able to fold/unfold my tent without problems once it's inside.

 

[Martyn]

Martyn I googled "mattress condensation" and the 3rd result was this:

http://www.autohomeus.com/accessories/underMattress.php

I suppose it's similar to the Hypervent product. Autohome says:

The lightweight mesh construction is compression resistant (1 ton/meter2 )

That explains how air can move under the mattress even with the weight of the persons on top. I wonder if it would fold/unfold easily though. I found it on a Canadian Marine online store but it's 100$ for a 39" x 72" piece. It would require 4 of them to cover the 55" x 94" area of my tent.....that's a lot of money to spend without knowing if I'll be able to fold/unfold my tent without problems once it's inside.

My mind is tracking in a different direction here. If the metal skin and the fiberglass skin are having issues with condensation that is remedied by a breathable air space. Is it a non issue with wood floors because of their R value. Even in the tropics we didn't have this under mattress issue, even when mold started to grow in my wife's hair.:Wow1:

On your tent you could have the under mattress layer in two portions, one on each side of the hinge line.

 

[salsataco]

This stuff is very stiff and would not fold. Another boat trick is to use a heated fitted sheet that keeps the mattress dry. Probably not too comfortable for summer camping trips. You could also try to construct some sort of slat system for the mattress to lay on?

 

[EricGagne]

This stuff is very stiff and would not fold. Another boat trick is to use a heated fitted sheet that keeps the mattress dry. Probably not too comfortable for summer camping trips. You could also try to construct some sort of slat system for the mattress to lay on?

Thanks for the link on the Hypervent. I had no idea that under mattress condensation was a know problem for boaters and that solutions were available.

I think the autohome system might be better for RTT because it's much thinner. Hypervent seems nice but it's 3/4" and with the Campinglab's 3" mattress it could get difficult to fold.

The autohome also comes in 3 different sizes, their biggest one, cut into 4 pieces will cover most of my floor.

 

[EricGagne]

Somebody on my forum suggested a piece of cedar lattice, I wonder if it would do the job.

 

[Martyn]

Somebody on my forum suggested a piece of cedar lattice, I wonder if it would do the job.

Less expensive, would promote air flow, if it didn't work you could use it to trellis some tomatoes

 

[EricGagne]

I guess it's worth trying, if it doesn't work I'm not gonna lose much. These come with a few choices on the size of the openings, I suppose that big open squares would be better.........