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Sustainable dehumidification for a "dry room"  RSS feed

 
Mike Jay
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Hello permies!  I've come to realize that I have many microclimates inside my house.  Warm coat closet = fermentation area.  Cool, dark, damp basement = root cellar.  Airy, light basement area = seed drying. 

The one microclimate I don't have but would really like is a cool, dark and DRY area for storing seeds, grains, canned goods, etc.  It's humidish here for 6 months of the year (dew point 55-70).  I can section off an area of my basement for the purpose and seal it up to prevent air exchange, but how do I dry it out sustainably?

I could put in a tiny dehumidifier.  I could rig up some kind of a desiccant (suggestions?).  Are there other ways?

Thanks!
 
Genevieve Higgs
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Our smallish (2 bedroom 1 bath ) house is soggy and a single dehumidifier keeps it nice and dry through west-coast winters.  It doesn't seem to use too much electricity and can even permit us to rack dry clothes indoors all winter.  BUT it does heat things up to the point it is our primary heat source spring and fall.
 
Cody DeBaun
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I've wondered about the mechanics of this as well. My thought process on it so far has gone something like this:

- When air cools, it loses moisture due to condensation
- When it warms, it *can* take up moisture again
- A system that cools incoming air and drains off the condensation, then allows the air to warm back up again without any exposure to another moisture source would result in drier air
- Or doesn't let the air warm up?

I dunno, as you can tell from the complete lack of facts or figures this is purely conceptual on my end. I don't know that this would work, or if it would reduce the moisture level sufficient to create the conditions you're looking for. With some knowhow and experimentation though, I would bet you could dry air simply by passing it through a length of earth tube with a well placed water catchment/drain system. Maybe taking air from a warmer part of the house and putting it through that tube (ideally in a passive flow) might yield the greatest moisture change....

Of course the whole thing would probably work better if you crammed one of those H2out style silica gel canisters in one end of the tube


(edited to include silica gel cramming)
 
Mike Jay
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Cody, the process you're describing is basically how a dehumidifier works.  I'm not sure how dry I need this room to be but 40% humidity at 60-65 degrees would probably work well.  According to my little dew point chart, to condense water from that air, it would have to be cooled down to 35-40 degrees.  I could do that in the winter by channeling the air outside.  Or just swapping some inside air for dry outside air.  But I wouldn't have a way to do it in the summer.  Our earth is probably 50 degrees which would condense 60 degree air down to 70% humidity (still too wet).

I just checked Amazon for silica gel and they do sell big buckets of it.  Some color changes when it's halfway filled with water.  And you can put it in the oven to dry it back out and reuse.  That could be a solution.  I couldn't easily determine how dry the silica can make it in an enclosed space.  And it looks like there is a pink indicating one that is safer and a blue one that has toxic gick in it.
 
Cody DeBaun
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Might be worth a whirl.

Reading a little bit more about condensation, I'm wondering if you might get dryer air by tilting the pipe, such that the inlet is higher than the outlet? Moist air is lighter than dry air, so that air which touches the walls of the pipe and loses moisture first would first... is that right?

I don't know if that would lead to overall dryer air or just more time between bakes for the silica gel.

Mostly I think I'm just hoping that if I say 'I don't know' enough times someone with a better understanding of fluid dynamics, gasses and humidity will come along and drop some wisdom.

*There's no place like Permies, There's no place like Permies, There's no please like Permies*
 
Roberto pokachinni
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You could maybe have a well lit room full of succulents, like Aloe, that serves as the air intake for the space, and another for the air outlet, and all you would need is a fan to move the air between the rooms.  The succulents would draw humidity from the air that they need for growth.  Initially you would need to water them, but once established they would dehumidify the air in order to drink.  Never tried this, but thought of it a while back.
 
Mike Jay
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Robert, that's an interesting thought.  Using plants to consume the water in the air.  It would be a challenge for this particular application since they'd need CO2 so some air would have to enter and leave the "system".  And then it would accept humidity with that air.  And I'd have to have two chambers, one that's dark for the storage and one that's light for the plants.

But I like the concept.  For things like living areas where you already have plenty of CO2 and light they could potentially draw humidity out of the air.  Neat thought!
 
Dale Hodgins
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If the area has very little air coming in or out, you could simply hang a few flannel sheets. They would absorb moisture. Hang them in a sunny window first, to get their moisture level down to a bare minimum.

Wool, will also absorb moisture, as will sawdust. Cedar sawdust has the added benefit of deterring moths.
 
Mike Jay
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Sawdust and planer shavings I have plenty of.  Do you know how dry that would make it?  I can seal up the closet/room pretty well to prevent air infiltration. 

I've heard of using rice for this as well.  Any other common materials that I could use?  Does anyone know how low a humidity level any of these materials would provide?

If I was fancy I could put the sawdust in permeable bags and cook them in the solar oven to dry them out every once in a while.  If I was really fancy I could weigh the bag when it's dry and figure out when it needs to be redried by how heavy it's become.
 
Dale Hodgins
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I accidentally created a dehumidifier in my room when I was a teenager. I had a rabbit hide that I was trying to dry out, by putting salt on it. At first, the salt got wet, and I figured that it was drying out the hide. But it happened  every day for a couple of weeks, and the hide seemed as thick as ever. I was gathering moisture from the room, and it was dripping into the pan under the hide. My room was in a damp basement.

I'm not sure how well this would work in a drier room, but it might be worth a try. Instead of using a rabbit hide, a towel could be soaked in salty water and then allowed to dry out, with the salt covering it. It could then be hung up, to allow any moisture gathered, to drip into a collection tray. The salt would never be lost, since it could be dehydrated and used again.

There's probably a special type of salt that would work better. A tray filled with rock salt, might be able to collect water. The salt could sit on some sort of screen, so that water drips down into a tray. Save this water and dry out the fluid in a separate area.
 
Mike Jay
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Just found this info on a salt or silica base diy dehumidifier.  I'm surprised the media can absorb water and then somehow release it to drop into the collection container. 

Hunker
 
Roberto pokachinni
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Sawdust and planer shavings I have plenty of


If I was fancy I could put the sawdust in permeable bags and cook them in the solar oven to dry them out every once in a while.


I think this is your way to go, Mike.  Wood is always seeking humidity equilibrium and shavings and sawdust have great surface area to make that energy transfer. If you could hang pillow cases (or burlap sacks might be better) from the corners of the ceiling and put one each in the corners by the floor, this would probably accomplish the task pretty easily.  Rotating the 8 bags with another 8 that are in the solar drier (or something to that effect), throughout your humid season might likely be adequate to the task.

A good salt system might be a great addition to this, using the solar oven to dry the salt out as well.   
 
Mike Jay
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Thanks Roberto, a burlap sack of cedar planer shavings sounds like a perfect solution.  I think I'll go with that and see how dry it makes the room.  If I need it drier, I can try salt.  If that doesn't work, I can get silica gel.

Thanks team
 
Roberto pokachinni
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You could put a smaller cloth sack of salt in the center of a bag of chips/shavings.  Or you could salt the shavings by soaking them in a saturated solution of salt water and then drying them out before adding the shavings to the sack.   ...I just took a permaculture design course with geoff lawton this year and one of the earlier modules included making random assemblies of data.    It helps one come up with ideas that one might not have thought of.
 
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