Crawl space root cellars

Helloooooooooo,
So yeh. We have a crawl space and we want a root cellar. We live in Red Lodge, MT. It’s underground, somewhat heated because of all the heat making things down there, and so it’s also ventilated. I don’t think there are mice down there but I thought about just setting it all in a tub and making it so no mice could get to it. We don’t need to store a ton of stuff at this point. Should we just try it out with onions and see how long they last?? Any suggestions? Put a thermometer down there and see what the actual temp is? I already have a ton of projects and don’t really feel like making this into another big one. Thanks!

thermometer to start with, probably? bonus points if it’s one that records the lowest temp.

it must be fairly well insulated if it actually feels warm. i assume your lows there in montana are lower than here in western nc, and it definitely freezes in our crawl space when we see temps in the teens or lower.

Yes, sticking a thermometer down there would be a great start.

Ideally, a root cellar should be close to 32F, but not drop below that for ideal vegetable storage. If I was storing canning, I wouldn't risk it that cold as it's one thing for a carrot to freeze and another thing for a glass jar to.
There are veggies - like onions - who like it a bit warmer, so ideal root cellars have colder zones and warmer zones.
You'll likely have more consistent temps on the north wall. My parents house had a walled off area that was insulated from the rest of the basement, but not from the foundation wall and it did the job unless we had a protracted cold snap. You want a quick project, but even recycled bubble wrap draped down to "trap" the cold of a north wall could get you a cool spot without it freezing. Ideally, you would check the temp first thing in the morning for a while to see what the trends are and how it tracks with outdoor temps.

Rats and mice will be attracted to the smell of fruit and veg and they can chew through plastic, so the thicker the better or look for metal buckets/tubs. The tubs themselves need airflow, so consider using hardware cloth to make mouse-proof lids or drill small holes to allow airflow. That said, last year I used buckets with potatoes layered in sawdust inside a broken freezer inside an insulated out-building and they lasted far longer than any other system I've tried in the past. We generally get only a little below freezing weather.

I think it would definitely be possible to do this as a quick project. Friends I know who used to have a crawl space did get a pair of movers dolly's and fashioned a "cart" so they didn't actually have to wreck their knees crawling on concrete.

Throw a thermometer down or just some onions/potatoes and see how it goes, a plastic tub with some ventilation holes sounds a good idea, but watch out for it being chewed through.

I agree with Skandi. It doesn't have to be a big project, and it never hurts to experiment on a small scale. See how it goes. You'll gain useful information either way.

When you say "crawl space", how tall is it? Maybe it's because I'll soon turn 73 but you may tire of crawling on your hands & knees to retrieve your potatoes. If you really want to use a crawl space that way, you may want to have a firm floor and get a dolly or 2 or 3 dollies with ropes so you can pull your stuff out when you want it. If it is possible, you may want to enlarge that crawl space deeper, with a door you can access from the house. Of course, you don't want to weaken your foundations either by digging close to a wall or much lower than the foundations.
If your garage is insulated, or if you have an area of the garage or a basement you can close off, or an attic you can get quick access to, those may be much better options. Bins built with 1/4"wire and a lid will offer the protection against mice that are sure to get interested in your wonderful goodies!
Your onions, garlic, sweet potatoes will fare much better in a closet, inside the house. Sweet potatoes in particular just cannot handle the cold.
Another benefit to using spaces that are in areas of the house most travelled is that your stuff will actually get used, whereas if you have to wade in the snow or crawl under your house/ deck to fetch something, you will find you are not that hungry after all, and perhaps quick mashed potatoes from a cardboard box will have more appeal. Ask me how I know.
The University of Maine suggests 3 different types of storage: cold, cool and warm, by ideal temperature and humidity.
https://extension.umaine.edu/publications/4135e/

Very interested in how this has worked for anyone. We are building a log home in New Mexico and it will have a crawlspace with 4 feet between the bottom of the floor joists and the floor of the crawlsapce. Compliance with the 2018 IECC requires an insulated, but unvented crawlspace. All but about 8 inches will be below ground. The property is at 7300 feet of elevation, Zone 5B.

Joshua States wrote:Very interested in how this has worked for anyone. We are building a log home in New Mexico and it will have a crawlspace with 4 feet between the bottom of the floor joists and the floor of the crawlspace. Compliance with the 2018 IECC requires an insulated, but unvented crawlspace. All but about 8 inches will be below ground. The property is at 7300 feet of elevation, Zone 5B.

As a relatively short woman, I find 4 feet manageable for short periods. If the area you turn into the "cool space" (with the insulated and unvented rule, I don't think it will qualify as "cold") is reasonably close to an access point that would help, but I think I would find or build some sort of wheeled chair and something like a "tea trolley" to load and unload things. It's one thing to bend over to walk. It's another thing entirely to do so while trying to carry buckets/bushels/boxes of food. Food can get pretty heavy! Similarly, you're going to have to look at labels, and move things around which is awkward when crouched over.

Is there a reason you've chosen 4 ft? Would it be possible to have an accessible area go deeper? I agree with Cécile totally - if you plan to live in the house a long time, you need to think of how it will work for you many years from now.

Thanks for the insight Jay. 4 feet came out of a lot of things, not least of which was the structural engineer's calculations.......and the cost prohibitive nature of a full depth basement. There are other considerations, like the subterranean rock shelf and the general lay of the land. I have designed the well system so that the holding tank sits on a pad that is 12" above the floof of the pump house. The floor of the house will be 3 feet below the bottom of the holding tank. In the inevitable case where we lose electricity, I will still be able to gravity feed the countertops, tubs, and toilets. (yes, we are considering a small PV system to power lights, fridge and freezer as a back up, but considering the heavy timber we have, I'm not sure how effective that will be without aserious power storage system and I hate batteries...) If the crawl space becomes unusable for a root cellar, I might just dig a small (120- 200 sq ft?) building into the side of the hill.

Stephanie Naftal wrote: We don’t need to store a ton of stuff at this point. Should we just try it out with onions and see how long they last?? Any suggestions? Put a thermometer down there and see what the actual temp is? I already have a ton of projects and don’t really feel like making this into another big one. Thanks!

Here are some helpful threads that might help you or some of our other readers:

https://permies.com/t/140268/Garbage-root-cellar-success

https://permies.com/t/62624/Retro-fit-floor-root-cellar

https://permies.com/t/34200/Making-underground-cellar-advice

I had seen a thread about someone using a crawlspace with some great pictures though I so far have not found it.

I suppose that New Mexico is quite dry or the rules would not suggest "unvented": Crawlspaces are typically dark and damp with lots of creepy crawlies, spiders and the like, maybe even mice. They are also an invitation to mold, mildew.
I too was wondering why 4 ft. of crawlspace? Is that a requirement for crawlspaces in NM? Why not 5ft or 5 ft. 6, which would create a much more useable space, not to mention greatly increase the resale value of your home...
Is it perhaps a tax question? Would you have to pay much more in taxes if your crawlspace becomes...  a basement? Look at what the law says is a basement (It is 8 ft. here, as a regular house has 10 ft. ceiling). Sometimes, the law is an ass but we could build 7 ft. 'basements' here and call it a crawlspace.
Now is the time to sweat these details, as long as you are in the construction phase. You might want to check if you can make it just a little taller legally. It will be a lot easier [and cheaper] in the long run, to build this house *exactly* the way you want it rather than try to retrofit this space to make it useable later.
In a 4 ft. crawlspace, I have to go on my hands and knees, and lugging around a couple of bushels of potatoes, that would not  be fun. I'm 5 ft. 3", so even a 5 ft. crawlspace would mean that I have to duck a little, but that would be quite  'workable'.
During the building phase, you could also decide to have this crawlspace "finished". By that I mean with solid,  vertical, concrete walls and floor or with a dirt floor.
I was wondering also if the *whole* crawlspace will have the same footprint as the home above. If you do, you could segregate an area for potatoes and another for onions, squash and the like that have different requirements? Following the walls of your rooms above would also give the crawlspace a lot more strength and functionality.
One good thing  is that you will have 8" above ground, which should give you "seeing light" at least on some walls [assuming that the whole footprint is occupied by the crawlspace]. Maybe even a possibility to vent when you need to. Indeed, why "unvented"? You could have a 'window' that stays shut when the inspector is around too. [No hinges, just pins that come off at a moment's notice and get replaced by a screen, also affixed by the same pins when you want to cool off the 'crawlspace'.]
Some basements have a sump pump, which is usually a 2'X2'X2' hole, stiffened with concrete. You sink a pump in it to avoid flooded basements in the spring especially. Here, in Wisconsin every home has a sump pump. I do not know of any that doesn't.
This just to say that all regulations have flexibility built in, and you can usually find a 'workaround'. If the regulations say 4 ft. is your max, just say: I want a sump pump, which I don't think they could deny you. Then, you could maybe decide to have a much bigger 'sump pump hole.' Just saying...
An insurance agent came here telling us that we would have to have a railing around our deck. I asked why? She said "any drop higher than 2 ft. requires a railing. It is the Law". So I built 2 very large planters along my L shaped deck, about 4 ft. high, which gives me exactly  a 1 ft. 11" drop. Where there is a will, there is a way.

OK folks. There seems to be some curiosity about the crawl space planning. I will try to clarify.
First a confession of sorts. During the day, M-F, I am a building code guru for a rather large municipality in the Siuthwestern USA. As such I keep abreast of advancements in building technology. I know it's not exactly the sort of thing that "Permaculture" brings to mind, but there it is. The unvented crawlspace is a product of the International Energy Conservation Code (IECC).  I guess the best way I can describe the rationale behind the IECC is getting people to live inside a Yeti Cooler. So the entire crawlspace is also insulated. The last thing you want to do with a well insulated building envelope is to cut holes in it and let the outside air pass through. Hence the unvented design. Air exchange is managed through measured transfer ducts and timers. Humidity is regulated by dehumidification equipment. The house sits at 7300 feet above sea level and I think I have it designed to the point where the crawlspace should stay a pleasant 40-50 degrees F all year round. We will see. It may get cooler in the winter.

As for the height, I think I already went over that, but here it is again. The land rises away to the north of the house. The well is drilled uphill, and I have a 1000 gallon holding tank uphill from that. The well pumps water up into the tank. The tank bottom is 1 ft above the floor of the pump house and 3 feet above the floor of the main house. In the event of electrical outage, the water will still gravity feed the kitchen sinks, toilets, and bathtubs. Could I have accomplished this by digging a full basement? yes, but that would have meant excavating a 1500 square foot hole 8-9 feet deep. That's a lot of dirt to deal with, like 445 cubic yards of dirt. You cannot sell it (think about the phrase "dirt cheap") and it costs money to truck it away. Using the natural lay of the land, I am able to dig 2 feet down, place my footings and build a 4 ft crawlspace. The 2 feet of dirt gets used as backfill to cover the crawlspace walls, and bring the grade up, both under and in front of the porches so I don't need those pesky guard rails......

I'm not really worried about fooling the building inspector. I supervise buiding inspectors for a living and I know the building codes better than most of them. We have a saying in the biz: Inspect for the minimum requirements, but build for the exceptions. There are lots of basic rules in the codes, but there are also many exceptions to those rules. I can take advantage of those exceptions, because I know what they are. I mostly built the crawlspace at 4 feet because the engineer who designed the foundation calculated that as the minimum required. The frost dept is 3 feet required to the bottom of the footing from the top of finished grade. Why dig down 3 feet and then leave a small crawlspace that you have to get on your belly to navigate? The stem walls will be three feet tall just to get above the exterior grade. Adding an extra foot was the perfect balance between excavation and masonry costs.

If the crawlspace doesn't work as a root cellar, I will dig horizontally into the hill and build a walk-in root cellar where everyting is under ground except the entry door.

Good planning. sounds like you thought of everything.