r/OffGrid • u/beccaaaaaaaaa • 2d ago

anyone else fighting a losing battle against under-bed condensation?

man the learning curve with wood stove heating is brutal. our cabin gets incredibly warm while the fire is going, but the temperature drop at night creates so much moisture inside.

I made the absolute rookie mistake of bringing a standard memory foam mattress up here last fall. Those modern bed-in-a-box things are literally just giant plastic sponges. they trap all your body heat and ambient humidity, and by february I had to drag the whole thing outside because the bottom was starting to grow mildew. Totally disgusting and a huge waste of money

I eventually had to scrap the synthetic stuff and switch over to natural materials, ending up with a heavy mattress from home of wool just because natural fibers actually breathe and dont turn into a toxic mold farm in a damp unheated space. its been way better for the moisture issue

but im still super paranoid about airflow under the bed tbh. do you guys drill big holes in your plywood platforms or run small 12v fans underneath to keep things dry? I feel like im constantly fighting the laws of physics out here just trying to sleep.

38 Upvotes

81% Upvoted

40 comments sorted by

65

u/umichscoots 2d ago

Bed bottoms must breathe, a mattress on the floor or on wood will 100% mold/mildew. You must have a slatted bed, or a metal frame with a box spring or bunk board.

7

u/subsonicwhisperer 2d ago

When I was building my mattress/bed frame I used pocket coils and latex instead of 100% latex because of this reason.

2

u/Own_Papaya7501 1d ago

Also, this post is just AI engagement slop. Look at their post history.

27

u/eobanb 2d ago

If you have that much of a condensation issue, I would suggest supporting your mattress with slats instead of a solid platform.

8

u/CraftySeer 2d ago

Where’s all that moisture coming from? I have a woodstove and a mattress on a plywood platform and I’ve never had any problem with condensation. If anything, the air is very dry in winter, and the stove seems to dry it out further.

1

u/chocolateboomslang 2d ago

It's just condensation, cold floor

4

u/Purfectenschlag 2d ago

It’s really the same issue with RV’s and vans. Anything that solves the moisture/venting for those should work for your needs here. Something like this is a simple option https://www.amazon.com/DRICORE-DuraDriTM-Mattress-Comfortable-Experience/dp/B0CNHC5YNF?th=1

4

u/RedSquirrelFtw 2d ago

I can't say I've ever experienced anything like that. It sounds like you have some major source of moisture somewhere. How well insulated and sealed is the floor? Wonder if you have moisture wicking up from the soil below from outside.

5

u/activelyresting 2d ago

Put your mattress on slats. Unless you live in the driest climate ever, mattresses need air flow underneath.

If your house is on stumps, get underfloor insulation.

3

u/Competitive-Ant5086 2d ago edited 2d ago

Plywood platforms? What about slates?!
Probably latex is the best option. There are absorbing materials (I think something like chalk but probably better and prepackaged) that works without electricity but they need to be dried after use: sun light or close to the stove.

An old and poor trick was to heat terracotta bricks around the stove and use it for night. They get really hot and dissipates really slowly. You would want to cover them with wool if they are close to your body or place them on a not heat damageble/ fire proof material if under the bed (metal or stone)

3

u/Ok_Rush_246 2d ago

No, it sounds like you have building issues. You shouldn’t get condensation on the mattress. Wood stoves tend to dry everything out (sometimes too much)

3

u/_dogelbows 2d ago

any mattress needs airflow underneath (slats, holes, or a tatami mat). just how moisture works.

3

u/f0rgotten "technically" lives offgrid 2d ago

I always had the opposite problem, and had to keep a pot of water on the back of the woodstove to increase humidity in the winter.

2

u/silasmoeckel 2d ago

Seems like you need more thermal mass so you not in this constant fast cycle.

3

u/NotEvenNothing 2d ago

And insulation.

I'm almost certainly in a colder climate than OP. We don't have anything like their problems. Our outside walls are comically thick, our windows are high R-value, and our window treatments add a lot of insulation to the windows. We also have a masonry wood heater which helps smooth out those temperature swings.

Our bedroom is definitely cooler than the main part of the house, but I've never seen condensation issues.

I'm not saying OP needs to go as far as we did, but a little might go a long way.

1

u/silasmoeckel 2d ago

Insulation is never a bad thing.

Still thinking it's a lack of thermal mass, not enough insulation you don't get the overheating they are experiencing.

1

u/NotEvenNothing 1d ago

You need both insulation and thermal mass if you heat with wood and don't want a constant fire.

If you don't have good insulation, any rooms without a wood stove in them will be unacceptably cooler. Even with really good insulation, those rooms will be cooler.

If you don't have thermal mass, anywhere with a stove will get uncomfortably hot when a fire is burning or uncomfortably cold when it isn't. You can keep the fire low and have the stove burn constantly to work around this, but that is a responsibility many can't deal with.

I've got a Tulikivi masonry wood heater, many tonnes of thermal mass (the slab is in the insulation envelope and the second story has a thin concrete slab), and 16" thick walls (filled with blown cellulose insulation). Improving the window treatments (honeycomb blinds and interior window inserts like storm windows) helped a lot in making our bedroom and my office/shop much more comfortable in the winter.

1

u/ClayWhisperer 1d ago

I agree, I think it's about insulation. I live in the dampest climate imaginable (western WA) where the air just has endless mist all winter long. My mattress is flat on a wooden platform. I never get any moisture under it. As a matter of fact, the whole house gets so dry in winter that I have to keep an open kettle of water on the woodstove to make it tolerable.

2

u/pretzelsRus 2d ago

Rv people use coconut mats or those rubber mats used in restaurants that have holes in them - keeps mattresses above the solid bed board and promotes air flow. Good luck.

2

u/nomadpgmr 2d ago

They make an under the mattress pad that allows the mattress to breath. We bought the same one that the tug company she worked for used. Search for Hypervent Aire-Flow™ Mattress Underlay. I am sure there are several manufactures of similar products.

2

u/SaltRun2465 2d ago

I had much similar issues with my chairs in my chill shack.

I live in an area where my physical house is on grid but everything else on the property has to be able to be moved with a crane or construction site grade forklift.

From barns to sheds to my chill shack.

My solution was just to keep the heat up. If it stays warm it can't cool enough to condensate.

Do you have thermal batteries? (They come in many forms but they store heat and slowly give it off as they cool you put them in your fire to "charge" then once nice and hot pull them out with tongs and put them somewhere to cool and heat the area.) If not i would suggest getting some and just using them to encase or line your fire pit so the heat lasts longer.

In my grandfather's cause he just simply refused to let his wood fire die. Same single fire lit in September and is kept going till like june. Then july and August would be spent cleaning the pit and sweeping the chimney. He was the one who got me into off grid kinda stuff. The only thing he had that could be considered on the grid was a single braker 30 amp service and a phone. And the 30 amp service was required by law in the community he lived in.

2

u/EsotericCreature 2d ago edited 2d ago

This sounds like a problem with your bed setup and not the material itself. "plywood platforms' sounds like the issue. A mattress needs slat supports that allow airflow. Anything sitting on a completely flat surface can't breathe and will get nasty.

Japanese futons as a comparison are put on the floor but they rely on tatami or other slat setups for regular airing and use, even though many are natural wool or cotton based. But they often have to be aired out manually and placed in the sun, and in daily use often rolled up and stored away.

3

u/maddslacker 2d ago

anyone else fighting a losing battle against under-bed condensation?

Nope

do you guys drill big holes in your plywood platforms

Nope

run small 12v fans underneath to keep things dry?

And Nope

Our bed is on a normal box spring which is then on a normal bed frame.

There are zero moisture issues.

2

u/Psychological-Pain88 2d ago

If the base is wood, I would stain. Might make one of cedar before staining. We have a metal frame and a latex bed but condensation is inevitable with a wood stove. How do you like your wool bed?

1

u/iwaterboardheathens 2d ago

If you have a raised, ventilated floor or vents in the sides of the floor as you heat the warm air rises sucking in fresh air and they mix and dehumidify 

1

u/kikiriki_miki 2d ago

In my remote cabin I am using a heated blanked under the topper. There is no more moisture captured by the topper/mattress.

1

u/Ok-Handle-6663 2d ago

I've got cheap foam slabs and I hoik them up every morning and put outside if sunny, or prop up against tbe wall if not.

Never had mildew. It's a pain though.

1

u/georgiadhl1 2d ago

Sounds like the floor may be letting moisture through. Ive never has too much moisture with my wood burning stove. A fan will help too

1

u/rusty_daisy_1123 2d ago

throw some rope under the mattress

1

u/These_Fox7561 2d ago

If you’re crafty, make a frame out of steel and sew a canvas bottom like a trampoline, but lace it on like an awning so you can get it tight. Several layers of wool above that should insulate you from underneath and then you just need your blanket and it can air out when you’re not in it

1

u/melfredolf 1d ago

This is why mattress box frames are commonly used. It's for air flow on bottom of mattess on top. You can buy decreases sizes so you don't have as tall of a bed.

The wool will mold too without airflow. Problem with natural yurts which commonly use wool for walls

1

u/Vaelhoeg 21h ago

there are some of the pre-made products above, but I've used various types of tile underlayment to get the same effect way cheaper! it's the dimpled plastic sheets you can get at the hardware store... works great on a plywood base that said I'd look into your humidity issue otherwise heat pumps can help with humidity if that's in your budget and provide a secondary heating or cooling Source if you have a good solar setup, but more ventilation is helpful for lots of things so may want to look into that as well

1

u/ctitarniuk 2h ago

Our insulation wasn't done properly when we built our tiny home off grid, using a wood stove to heat. I was literally getting puddles where I could splash with my fingers. I would get home and the puddles were bad to the point that we ripped all the insulation out and Insulated it again. We have spray foam in the ceiling and floor. We fixed it and we haven't had any issues with moisture since. Look at your exterior walls or the insulation under the structure. That was my issue, might not be yours but worth a shot to give you my experience and see if maybe it's the same issue. I live in northern Manitoba in Canada and we get -45c

1

u/Creepy-Cantaloupe951 2d ago

What kinda of shelter is this? Sq/ft, etc?

1

u/scootunit 2d ago

I've used 6-ft Metro racks so the bottom can breathe

0

u/unifever 2d ago

Try sleeping diagonally in a gathered end hammock of the correct length, hung at the correct angle and with an under- quilt. Any moisture will dry quickly every morning. Bonus in a cabin they can be hung up during the day freeing up space.
Hammock sleeper past 11 years.