Fermenting in Cold Houses

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Our house is generally on the cool side, between 65 and 68 degrees Fahrenheit, in the fall through spring months. This can make fermenting projects such as kefir, kombucha, yogurt, et cetera a bit dicey, as the cultures tend to appreciate warmer temps. Fermentation slows down considerably in cooler temperatures.

Is your house the same way? Fear not, intrepid whole foodies!

How to ferment in a cool or cold home

It’s so stinking easy, and cheap to boot. Buy one of these:

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Before appropriating my own germination mat to sprout my pepper seeds, it had been in use in the kitchen, keeping my kefir cultures happily warmed. It never gets to be Too Hot. When I was drinking a metric honkload of kefir daily, my grains easily fermented a half-gallon every 24 hours on this mat.

For the gardening enthusiast, germination mats will increase germination rates and keep the root areas gently toasty. The first year I tried to grow peppers, not a one of them sprouted – it was too cold in the basement, even under the grow lamps. Last year, my step-mom gave me a germination mat and I’ve had no troubles since then.

Admittedly, it didn’t immediately occur to me to use the germination mat for fermenting, but I’m sure glad the thought eventually percolated into my dense skull!

A variety of sizes are available, from the 20″ x 10″ one listed here, to giant honking 40″ x 20″ varieties.

They are durable, immune to moisture, and will last for years and years. Love these things!

Here’s a new setup for us in the dining room: I found the shelves at Goodwill for a ridiculously low price, got the washing board at the local antique store, and the cookie jar belonged to my mom. The fermentation mat is under the Mason jars. We currently have a half-gallon of kombucha, a half-gallon of yogurt, a quart of kefir, and a pint of yogurt mother culture brewing away on the small-sized mat.

Kefir, kombucha, yogurt, and yogurt mother culture all fermenting on a germination mat

Ideally, fermentation should be done in a dark place, like a cupboard or cabinet. However, we don’t have any with electrical outlets; thus, the dining room it is.

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5 responses to Fermenting in Cold Houses


  1. What a great idea! I have the same problem! Do you think a heating pad on low would work, too? The one I have is for dry or moist heat, so a little water won’t hurt it. Any thoughts?

  2. Erin D.

    Hi Jackie – Glad you found this helpful! I’ve wondered about heating pads myself, but the only ones we have shut themselves off after 30 minutes (newfangled, stupid safety measures.)

    I’m no heating pad safety expert, of course, but if you have one that can be set at a very low temperature that will stay on, I don’t see why it wouldn’t work. I might cover it with a towel, just to make sure the fermenting container doesn’t pinch a wire or something, and I wouldn’t put really heavy stuff on it, though.

    If you give it a go, let me know how it works!

    Thanks for commenting. 🙂

  3. My dad did something similar when he was brewing wine and beer, but he used an old water bed heater attached to a thermostatic regulator. The water bed heaters look very similar and are a bit bigger, which was perfect for his fermenting jars.

    • Erin D.

      Hey there! A water bed heater never would have occurred to me, never having seen such a thing. But heck, I’ll bet they’re *huge* and perfect for the task! Thanks very much for the suggestion!

  4. Erin D.

    I updated the post with a photo of our mat in action. 🙂

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