Ideal temperature and humidity for long term storage.

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Alaskajohn

Bugged out
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Oct 2, 2020
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Alaska
I significantly increased my cellar allowing me to move a lot of my preps to this wonderful new space. I store a bunch of items, including potatoes, carrots, long term and mid term food preps, rice, coffee, seeds, and other items including a shotgun. After careful monitoring of humidity and temps, I can maintain 52 degrees year round and humidity is at 31%, and this stays fairly constant year round as well.

I have a toyostove in the cellar (vented outdoors) to keep things from freezing in the winter. The lowest temp is 50, which is where I have it set. I have found a few places where the air drafts to the outside, and I can better seal this during our short summer months. The toyostove set at this temp also keeps the main level from freezing if we are gone for a few days. So I need to keep it on. It's very efficient and only burns through about $150 in fuel each year. It might be even more efficient when I fix the areas where I have a draft.

The previous owner had an Electrolux dehumidifier and I have it now working perfectly. Before I put it into use, I need to know what humidity I should try to maintain for optimal conditions for the wide variety of items I store in the cellar.

Any thoughts on what conventional wisdom says is ideal temps and humidity now that I have a place to store such a wide variety of preps?

Thanks!
 
I significantly increased my cellar allowing me to move a lot of my preps to this wonderful new space. I store a bunch of items, including potatoes, carrots, long term and mid term food preps, rice, coffee, seeds, and other items including a shotgun. After careful monitoring of humidity and temps, I can maintain 52 degrees year round and humidity is at 31%, and this stays fairly constant year round as well.

I have a toyostove in the cellar (vented outdoors) to keep things from freezing in the winter. The lowest temp is 50, which is where I have it set. I have found a few places where the air drafts to the outside, and I can better seal this during our short summer months. The toyostove set at this temp also keeps the main level from freezing if we are gone for a few days. So I need to keep it on. It's very efficient and only burns through about $150 in fuel each year. It might be even more efficient when I fix the areas where I have a draft.

The previous owner had an Electrolux dehumidifier and I have it now working perfectly. Before I put it into use, I need to know what humidity I should try to maintain for optimal conditions for the wide variety of items I store in the cellar.

Any thoughts on what conventional wisdom says is ideal temps and humidity now that I have a place to store such a wide variety of preps?

Thanks!
I just ordered but have not yet received the book "Root Cellaring" so can't say, but @Bacpacker said he has the book - maybe he will chime in here.
 
I just ordered but have not yet received the book "Root Cellaring" so can't say, but @Bacpacker said he has the book - maybe he will chime in here.

Ordered! I know my issue might be a bit complicated as I store more than food, so I need to potentially compromise. But this should be a useful book!
 
IMHO, anything under 50% humidity is good. For temps, I go with 40-65°.
Have you been using that dehumidifier to maintain those conditions or just starting to use it now? In my experience, they're power hungry hogs. I've seen my electric bill jump by 30% using one of them for a month.
 
My basement is ranging from 45 to 60 degrees, and I'm keeping humidity in the low 30's but running a dehumidifier. It's draining into the sump pump well, and shuts itself off at 32. Before that, summer humidity was too high and cans were rusting up. Our bill wasn't too terrible running it, and it's mostly on in the summer and fall.
 
IMHO, anything under 50% humidity is good. For temps, I go with 40-65°.
Have you been using that dehumidifier to maintain those conditions or just starting to use it now? In my experience, they're power hungry hogs. I've seen my electric bill jump by 30% using one of them for a month.

I have just tinkered with it and verified that it works. I have not put it to use. 52 degrees year round and an approximate 30% humidity are without the de-humidifier.

The conditions that made the previous owners need to use it each spring no longer exist after my very expensive expansion project. I solved multiple issues with that expansion and had to hire a contractor. Getting a contractor with a big excavator and equipment to lift the cabin, plus bring in the cement trucks to the middle of nowhere took over three years to coordinate and plan! That is one of the reason why I went so big. The project included needing to build a road where a road didn't exist. When my dad past about 5 years ago, that is what I used the very small inheritance for. It just covered the project. That road is now going back to nature quickly and in a couple more years no one will know a road was put in there! The upper part near the cabin is growing natural edible grains, a suggestion of a fellow board member (thanks @Sourdough), but the lower part already has willow and trees growing, plus some other natural barriers I put it.

If 30% is acceptable, I won't be using the de-humidifier. Some of the literature suggested humidity below 15%, which has prompted this thread. I want to make the very most out of what my dad gave me!
 
Before that, summer humidity was too high and cans were rusting up. Our bill wasn't too terrible running it, and it's mostly on in the summer and fall.
Compared to a dehumidifier, I found it actually cheaper to run the whole house fan 24/7 and circulate the basement air with the main part of the house. When your A/C runs in the summer, it also dehumidifies. I let the A/C run through the basement as well.
 
I am going to put this here and might also put it in the food preserving thread. There is a book that I read some time back. I had to go searching for it, and my library only keeps a certain number of books in the history file - grrr. The book is "Cottesbrook: An English Kitchen Garden" by Susan Campbell & Hugh Palmer. It is about a castle in England that at the time was one of the only remaining places that still grew and cooked from the kitchen garden year-around. It discussed the different storage methods used for different foods. I recall potatoes had their own "cellar" - might have been called something else. I don't know how many of us here have English castles with kitchen gardens 😂 but I try to glean the relevant bits of info. that I might be able to use.
 
I keep potatoes, yams, and winter squash in the basement with no problems. Onions are upstairs.
High humidity gives me grief with rusty canning lids and rusty store bought canned food. Don't have that problems any more. I think running our ac in the basement would be more expensive than our dehumidifier. Although the add on is almost finished...a 25 by 25 sealed basement...no windows but there is electricity, no exit door. It will be a different environment than the other old basement that I use.
 
I have lived in desert places where the humidity would get down to the low teens in the late afternoon (which is typically the time of day when the humidity is lowest). In that atmosphere you need to drink more water than normal and your skin dries out. But where the priority is storing food, lower humidity may be the best (all though any fresh food in open storage will dry out more quickly).

If I had to guess, I would say 15-20 would be ideal and 20-30 would still be generally OK.

If most of your food is in cans or mylar bags, then go as low as is cost-effective.
 
Good thread! It sounds like I am OK. I’ll probably just keep an eye on it and only turn on the dehumidifier if and when I see it creep up. Everything has been really stable since I put the monitor in the cellar. I could also experiment to see how my energy cost goes up if I set the dehumidifier to 20%, for example.
 
I don't have any experience with the storage aspect of this, but I will say that my central A/C keeps the house in the low 50%'s during peak humidity season. I've read 40-60% is ideal for living spaces. If you dehumidify a space that is already air conditioned, that will lower the load on the dehumidifier.

Also remember that most of the time when people discuss humidity, they're talking about relative humidity, which changes with temperature. I prefer using dewpoint when the moisture content of air is the focus. My house is at a roughly 50F dew point in the summer, based on the below chart. But when that air settles into a 55F basement, suddenly its 85% RH. It's going to condense on any object that's about 50F, like the wall probably. The high RH is why poorly ventilated basements are prone to mold.

Keeping your cellar at <40%RH gives you a dew point below freezing, and will probably go a long way to preserving the stuff you keep in there.

1024px-Dewpoint-RH.svg.png
 
Some root veggies need a high humidity (80+) to store well.
Well isn't that a conundrum. If I was storing mixed goods, I'd keep the overall space at the lower humidity level, and then build a dedicated/sealed room with a humidifier for whatever needs it.

This is good to keep in mind for my next house. I wanted to partition off part of the basement for this type of storage. Sounds like I need to put more thought into it.
 
I just ordered but have not yet received the book "Root Cellaring" so can't say, but @Bacpacker said he has the book - maybe he will chime in here.

I found that book after we had our house built and realized that we had situated ours on the wrong corner of the house. I haven't read it in 10+ years so I'm not one to give advice. I do recall seeing charts that have a fairly wide range of humidity depending on what you are storing. Good regular airflow is very important as well.
 
Some root veggies need a high humidity to store well.

That was the main concern that I listed in my OP. What is the right balance for what I want to store there.

Most of the literature simply states store potatoes in a cool, dry place of about 43-50 degrees, so 52 is pretty close. Some other literature says store in high humidity, which isn't going to happen. The last 5 winters, stored in the in the previous cellar and the Yukon Golds lasted until mid April and they appear to be doing just as well. The purples haven't done as well, so we will either eat them quicker, plant less of them or plant something else. The carrots appear to be doing good too. I think part of my issue is finding the right compromise for those items that need low humidity and those that like higher humidity. Not sure if I can compartmentalize the cellar for various humidifies.
 
Potatoes store best in the ground. The rest get canned... or eaten. ;)
 
Potatoes store best in the ground.

Um, no! Not at -35 below zero. But I do like the eating them option! 👍 I will be dehydrating my excess potatoes going forward, but canning is certainly a great option too.
 
There is a pamphlet on cellar storage with a chart of temperatures, humidity and more at this link. I tried to copy it, but it didn't copy for me. It is an old usda pamphlet.

https://naldc.nal.usda.gov/download/CAT87213861/PDF

That is really cool! Some of the descriptions and illustrations remind me of our cellars in Appalachia and on the farm in Nebraska. The one in Nebraska was triple purposed including a nuclear fallout and a tornado shelter!
 
Almost all foodstuffs store best just above freezing. An exception is sweet potatoes and some squash which like it at low room temp.

Most things last longer with low humidity. Exceptions are root vegetables, but NOT onions which should be stored as dry as possible.

My store house is kept at 35º all winter long. In the summer it gets as high as 60º
 
That was the main concern that I listed in my OP. What is the right balance for what I want to store there.

Most of the literature simply states store potatoes in a cool, dry place of about 43-50 degrees, so 52 is pretty close. Some other literature says store in high humidity, which isn't going to happen. The last 5 winters, stored in the in the previous cellar and the Yukon Golds lasted until mid April and they appear to be doing just as well. The purples haven't done as well, so we will either eat them quicker, plant less of them or plant something else. The carrots appear to be doing good too. I think part of my issue is finding the right compromise for those items that need low humidity and those that like higher humidity. Not sure if I can compartmentalize the cellar for various humidifies.
You can put a pot on your Toyostove thermostat and turn down the factory lower limit.
 
You can put a pot on your Toyostove thermostat and turn down the factory lower limit.

It is at the lowest setting that I can have it at or my pipes will freeze in the main floor if I am gone for a few days. Its actually at the lower limit of 50 degrees on the dial. Any lower would result in a significant problem. I heat my main floor and 2nd story with a woodstove on the man floor, and the Toyostove's original purpose was to heat the main floor so nothing freezes. I set it at the level that protects the main floor. The 2nd floor, if I am gone, and during the 2 months where I don't get sun, will go down to 27 degrees, but this is not an issue when we aren't here. When the woodstove is going, the cellar actually goes up to 52 from 50. Of course, when the woodstove is going, the issue on the 2nd floor is it getting to hot, but this is what windows are for!

I need to find the balance of all my factors, humidity too high and my metal preps can rust, to low, not so good for potatoes, carrots, etc. The temp is where it need to be to accommodate all of my needs.

So really the only variable that is adjustable is humidity, but it looks like the 30% is a good place for all I am storing. From all the posts, it looks like where everything is at now is a good as I can make it!
 
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