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On Building an Urban Cellar

12.30.10

Over the past year or so I’ve been asked by more folks than I anticipated about how to tackle building their own cellar. And the more I find my winter writing heavily dominated by cellar-related adventures, the more I’ve realized that I’ll need to offer a resource about how to actually build a cellar if information about how to put one to use is to be of any value. If you have a home with a basement and live where it gets bloody cold in the winter, read on.

THE PREMISE The goal is simple: create a space with specific temperature and humidity. That’s it, really, so keep your focus there. How you reach that end will depend on the specifics of your situation, so your creativity and intuition should most definitely be engaged. If you have a spare corner of your basement, even a small one, you should be good to go.

Your first problem to solve is to figure out what you’re going to use the space for. Different food items have different needs, so the temp and rh [relative humidity] range you’ll need to shoot for will depend on your intended use. For example, many root vegetables store best at temperatures close to 0C, and 90%+ humidity – conditions only necessary from fall through spring when storing veg. If you want to geek-out on the details, check out resources like this. Wine, on the other hand, stores best closer to 13C and 60-80% humidity – and stability is important. Canning and onions need cold and dry. What to do? I’ve found a practical solution in building a single long room divided in half by an insulated wall and door. When you enter my cellar, it’s first, the root cellar. Its conditions are practical for root vegetables, hanging animals prior to butchery, cold stabilizing batches of wine, and general use as a walk-in fridge. Inside the root cellar is the door to the adjacent wine cellar. Although originally intended exclusively for wine, it is now sharing half the space with dry cured meats and cheese aging setups – two items that I discovered happily enjoy similar environments. With some ingenuity, the two spaces are accommodating all of my needs.

MANAGING TEMPERATURE Because you need cool-to-cold depending on your use, it’s considered optimal to site the cellar in a north-east corner, opposite the house’s furnace, clear of duct work or other heat generating items. Although mine is sited optimally, I get the feeling it would still be effective if sited in a variety of locations in my basement. So if optimal is a choice, perfect, if not, don’t sweat it, at least not this far north anyway.

Bare foundation walls provide good access to cold, but counter-intuitively do not insulate well and therefore also let in a good amount of summer heat, especially above grade, and especially if the sun hits it. A surprise to me in my research is that your summer cold source, important for wine/meat/cheese is actually the floor below your feet. The shade of your house and depth of soil keep that soil cool year-round. So my wine/meat/cheese cellar is essentially an insulated box, open on the bottom to capture heat from the cold floor. Imagine a cooler flipped upside down on your basement floor, upsized. It’s insulated with polyextruded styrene boards – effective in high humidity – and also a vapor barrier, sealed with tuck tape. It keeps cool in in the summer [peaks at about 15-16C in August briefly], and captures any humidity I introduce into the space – that’s its job.

My root cellar has quite different properties. The foundation wall is not insulated as summer heat is not a problem [not storing any veg then] – the rest is insulated the same as my wine cellar. Where things really change is that it’s vented to the exterior, allowing cold air in the fall to get into the space, cooling it down quickly, and allowing in seriously cold air in during the winter to get temps down near 0C with ease. In fact, at -20C outside or so, I have to plug the vents to prevent the room from freezing. I used the former window to build a setup that would allow a hot air vent at the top, under which is a cold air return that’s diverted diagonally across the room and to the floor to create circulation and draw.

MANAGING HUMIDITY We live in a dry climate, and managing humidity is a bit of a dance with nature. But I can tell you that my cellar would be at 20% humidity or less in the winter if I didn’t regulated it. Some folks use electronic humidistats that trigger ultrasonic humidifiers to very good effect – most often in re-purposed small fridges. I use a pail, old cloth diaper, and salt water. I let it drip off a shelf onto the floor, where it pools, and drags the humidity upward dramatically. So much so that when I put up large batches of meats to dry cure, I have to disengage the water setup to avoid exceeding 75%rh. In mid-late summer, the cellar’s at 75% rh or so naturally. I’ve tracked it for years, have geeky spreadsheets and charts, so you can trust me on this one.

MY SETUP. At the time I built my cellar [2009/10] my priorities were wine and root vegetables.

I built my wine cellar based on Richard Gold’s book. It has 2 foundation walls insulated with 4″ of polyextruded styrene boards [insulation proved to be the most expensive part of the build] and 2 walls built with 2X4 wood construction and pink insulation. The only tricky part is the custom insulated door, which I’ll leave to his book to describe. At 6X6X8′ it can hold about 40-50 cases of wine, a few hundred pounds of dry cured meats, and quite a few kilos of cheese. I wouldn’t want it bigger. It has bins 1′ deep on either side and an aisle just over 3′ wide down the middle. You can see some detail on the dry cured meat hanging setup here. I do find it a tad cold in the winter, 3-4C this winter, now that the root cellar is functional [it used to bottom at 8C pre-root cellar being finished]. I’m considering running some cold air ventilation out from the wine cellar into the adjacent unheated storage room. On the plus side, I’m also anticipating it now being colder in the summer simply due to residual cold.

My root cellar is slightly larger than my wine cellar, and size here isn’t king either. At 6x6x8 I figure I could put up about 2000lbs of vegetables at full capacity. You likely don’t need larger either. I built shelves out of 2X10, two deep, and have bins and tubs to accommodate food. 1″ shelves are not even close to strong enough. I tried and failed. Although I know others have done it, my ventilation setup is something I’ve never seen before – most people use a single hole to the exterior, which works. I’d wager mine provides better ventilation through the space. I can tell you that white plastic sewer pipe is cheaper than black plumbing ABS when running the cold air return. I put two threaded eye bolts into the joists overhead to be able to hang animals.

YOUR SETUP Although my setup works and I love it, I’ve since come across an idea that I would use if I had to do it again. Eliot Coleman [see recommended reading below] suggests using cinder blocks as your framing material. Genius. It has loads of thermal mass, and more importantly, will not rot in a high humidity environment. My wood setup will eventually be compromised by nature. Cinder blocks will not. Coleman takes a bucket of water down to the cellar when getting veg, splashes it on the walls and floor to retain high humidity,  and uses the bucket to collect veg. That guy’s a genius.

So if you’re serious about building yourself a cellar, get the books below out from the library, give them a read, figure out your needs and space, and before you know it, you’ll be rocking. If you have questions after reading the books, drop me an email.

Recommended Library Reading: How and Why to Build a Wine Cellar, Richard Gold; Root Cellaring: Natural Cold Storage of Fruits and Vegetables, Mike & Nancy Bubel; Four Season Harvest: How to Harvest Fresh Organic Vegetables From Your Home Garden All Year Long, Eliot Coleman.

9 Responses

  1. Mel says:

    Awesome guide. I’m totally stoked to start working on my cellar, though it’s going to take me a couple years to get both the cellar and garden fully functioning. Still, it’s great to have such good foundational knowledge.

  2. THANK YOU!!!!!! Now., I will have Vanja read this, and we will see what we can do. As you know, we have a considerable amount of unfinished space in the basement. Sounds like a project coming on!!! And, I will have you over to advise, should I get him to agree to this project!
    :)
    Thank you SO SO much!
    Valerie

  3. Mel – it takes time. I’ll look forward to seeing how you tackle it in your space.
    Valerie – I’d be happy to come by to take a look at where to put it!

  4. Happy New Year to you and Pam and the gals!!!
    We just got in from a great outdoor Nature Hike and I feel like a million bucks! I did it! I am still able! It was magic. Pure Magic!
    Hugs to all of you!
    :)
    valerie

  5. Greg says:

    Great synopsis and tips, thank you! We have the benefit of high humidity year-round (or so it has been thus far) including in the basement… which is prone to getting a ‘beard’ of frost in the winter… very hard on the foundation. We have a lot of work to do to stem that form of damage, but so much research and experimentation has been done by others that we should be able to fast-track our designs a bit.

    Houses out here on the range often have ice houses next to the home, and I’m envious (don’t know anyone who uses theirs, tho’!!!). Every winter I’m saying to myself, “I should be making ice right now.” Some might think it too rustic, but to me it’s all part of this neo-passive energy management program the most perceptive of us are enrolled in.

  6. Kevin says:

    Valerie – Happy New Year!
    Greg – I gave some thought recently to what you and I might do without the internet as a resource. Yikes. Making ice seems sensible to me if one could devise a simple way to tackle the job. Summer refrigeration is pretty important.

  7. Emily says:

    I live in Michigan and built a root cellar in my basement last year. I’m in the middle of my first season with it. I’m having a hard time keeping the humidity of the room above 50%, but what I find is I can keep the humidity in the *bins* up where it needs to be. Rubbermaid tubs filled with damp peat moss work pretty well, but the willow wicker hampers that layer potatoes and 3 sheets of newspaper work even better – no sprouting so far this year (October – end of January) and everything is firm and sound. I hope this works all season – it’s a lot less fuss, and I don’t worry about growing mold in the basement.

  8. Kevin says:

    Very well put. You’ve summed up my dad’s success with cellaring his veg despite his ‘cold room’ being as dry as it wants to be. It pleases me greatly, as it means that keeping the veg overwinter is essentially easier than I thought – and can be tackled a few different ways. Removes barriers to entry, which is fantastic. Thanks for sharing.

  9. [...] Kevin arrived with his arms laden and immediately started to prepare the charcuterie and cheese tasting course. All of the meats below have been made with his own hand and cured in his temperature controlled root cellar. [...]

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