Three Easy Ways To Insulate Your Worm Bin

Three Easy Ways To Insulate Your Worm Bin

With the winter months fast approaching, we have been getting a number of questions from readers who want to make sure their worms bin is ready.

  • “Can my worms survive outside through the winter?”
  • “How cold is too cold for my worms?”
  • “How can I insulate my worm bin from extreme cold?”

Well readers, it’s your lucky day! In this blog post, we will answer all these questions and teach you 3 easy ways to insulate your worm bin to help your worm colony to survive the winter. You won’t need a special suit for this insulation job!

This will ensure your worms are processing waste materials through the entire cold season, and will produce an ample supply of worm castings for you to use as soon as springtime rolls around. There is nothing worse than heading out to harvest your worm castings in the spring, only to find out that you need to replace your worms who all died months ago!

“Can my worms survive outside through the winter?”

When the cold winter months roll around, the best place for your worm bin is inside of the house. However, based on your living arrangements, this might not be possible. Many of our readers live in apartments with no-animal rules, or do not feel comfortable sharing their living space with hundreds, or even thousands, of worms.

If you find yourself in a similar situation, it is natural to wonder about the safety of your worms when they are left out in the cold. There is no short answer to this question. The safety of your worms really depends on a couple of variables.

  • How cold do temperatures get where you live?
  • Is your worm bin inside of a structure like a garage or a shed?
  • And last but not least, how much assistance are you willing to give your worms during this winter period?

“How cold is too cold for my worms?”

When people ask me about the prefered temperature range for their red wiggler worms, I ask them to think about the temperature range that they personally feel most comfortable in. Just like humans, red wigglers generally prefer temperatures in the 60-80 degree range. If you stand next to your worm bin and notice that you feel hot, it is likely that your worms feel hot as well. If you stand next to your bin and you feel a little chilly, your worms are feeling cold as well.

Now, that doesn’t mean that your worms can only survive in the 60-80 degree range. That just happens to be the temperatures in which your worm colony will do the best work. Your worms will be moving at maximum capacity while they process your waste materials into “black gold” worm castings.

When the temperature drops down below 60 degrees fahrenheit, your worms will keep on living and processing waste material, but at a much slower rate. Think of it like your refrigerator: lower temperatures make for slower decomposition.

When temperatures sink below 40 degrees, however, your worms will stop working and will begin to die off. Your goal for the winter is to keep your worm bin warmer than 40 degrees at all times. You can use a worm composting thermometer to take readings from different sections of your worm bin and ensure that the temperatures in the bin never get down to dangerous levels.

“How can I insulate my worm bin from extreme cold?”

There are a number of easy changes that you can make to your worm bin in order to help your worm colony survive the winter.

  • Provide your worms with shelter. The easiest change you could make to help increase the temperatures in your bin is to provide your worms with some sort of shelter from the elements. This shelter can take many forms. If you are lucky enough to have shed or garage access, you can move your worm bin there. Even if you do not have access to a structure like a garage or a shed, you can place your worms behind a barrier such as a fence or a large hedge. By protecting your worms from the wind, you slow down the rate at which the temperature fluctuates, keeping your bin within a more moderate temperature range. And if your bin came with a lid, put it on! Every little bit of shelter can make a huge difference to your worms!
  • Place an insulating layer on top of the bedding. A layer of presoaked newspaper can work wonders on your bin’s temperature! Make sure to soak the paper prior to adding it. Place a few layers of dry newspaper on top to absorb any excess moisture. The wet layer creates a thermal barrier which slows the transfer of heat out of your worm bin. You can also use a coconut coir mat or burlap bags for this purpose.
  • Insulate the sides of your worm bin. Much like the top of your bin, the sides of your worm bin need to be insulated with some sort of thermal barrier. I have seen many creative methods that worm farmers have used to insulate their bins. You can stack objects like hay bales around your bin for an easy fix. If you really want to get professional with it, you can attach blue board insulation foam, cut to fit. You can even dig a hole for your worm bin and insulate it with the surrounding earth for a more sustainable solution!

What’s next?

Now that you have insulated your worm bin to the best of your ability, you may be wondering what else you can do to help your worm workers survive. In another post on our site, we covered 5 easy steps to prepare your worms for winter.

The only thing you can really do now is monitor the temperatures in your worm bin, and help to heat it up when necessary. Using a worm composting thermometer, you can regularly check the temperature in your bin and see when it is getting dangerously cold.

When the temperature approaches 40 degrees, you can add leaves and yard clippings to your bin. These will let off heat as they decompose, giving your worms the extra boost in temperature they need to get through the particularly rough patches of winter. 

For more worm composting advice from the experts, sign up for our once-monthly newsletter with the bar at the top of your screen.

Have you insulated your worm bin some other way? Let us know how in the comments section below!

Article by Bob Kenney

Readers Comments (12)

  1. Do u have already food that can be purchased

    • Thanks for your question. We at The Squirm Firm are dedicated to educating, inspiring, and encouraging people like you to discover all the benefits of worm composting.

      The best food for your worms depends on your own worm composting goals. Our “What Can Red Wigglers Eat?” Infographic is a great place to start. You can find that on the right side of this page!

      Let us know if you have any questions and sign up now for our free monthly newsletter. Once a month we will deliver a useful set of tips, tricks, and tools for keeping your worm composting project going strong.

  2. My worm bin smells just a bit too much to keep it in the house, so I want to put it in my garage. I would like to know if I put my worm bin in a wood box, with 1.5 inch of foam insulation around all sides of my worm bin, with the reflective side of the insulation towards the worm bin, will the worms and compost generate enough heat to stay at their preferred temperature? I expect it to get down to 40’F in my garage over the worst part of winter. Would I need to get some sort of heater and thermostat? If so, can you recommend something? The foam insulation is rated at around R5 per inch from what I can tell. The reflecting aluminum may add some R value, I don’t know. What about 2 inches of foam insulation?

    • Hi, Allen!
      Thanks for your question. Your first order of business in this situation should really be to figure out why there is an odor coming from your worm bin. When the conditions inside are ideal you should smell nothing foul–not even up close. I’d suggest caring for that issue before bundling your worms up in potentially unhealthy conditions for the winter.

      As for your insulation plan, I would say that if you have a fairly well-established worm herd that can survive off of the contents of your bin through winter, you should be okay using both the wooden box and foam. Remember, worms are cold-blooded and will not generate heat of their own. Starchy foods you add to the bin may add a bit of heat but not much.

      Of course, any heat inside the bin will quickly escape if you ever open the bin during the winter. A heating element is a great option, especially if you want to keep your worms a bit more active during those chilly months. Some people use a heat rock typical of those used for lizards. You can find them at your local pet shop.

      Make sure to keep your bin off of your garage floor where cold cement would have contact with the worm bin. Cinder blocks can be used to give enough space for warmer air to circulate beneath the bin.

      Best of luck!

  3. I dug up about 30 worms on the first warm day in the year they are in my garage because it got cold again. The temperature of the soil is about 40 degrees will my worms die

    • Great question! I’m assuming that you dug up about 30 worms from outside rather than in your worm bin. If so, those worms are acclimated to the temperatures in your region and have survived the winter outside. It’s likely that you found earthworms. When it gets very cold, they burrow deep into the earth where it never freezes. They come up as the soil warms. They should be just fine in your garage if they’ve been placed into appropriate bedding and with some food. HOWEVER, if you have red wiggler compost worms that you’ve brought into 40-degree temps, they may or may not survive but will definitely be pretty inactive until temps get a bit higher. Best of luck!

  4. I would like to create a 4′ x4′ x 8″deep box to reprocess my organic potting soil between grows. Intend to add red wigglers and a bit of mulch throughout the winter. I live in Maine.

    The box will be outdoors sheltered from the wind but won’t get much sunshine. Outdoor temps will easily be in the -10° F at times -though on average – more in the 15° to 20° F range for 3 months but I’m confident I can insulate properly to keep my little friends active. Of course I will have snow cover too.

    My unanswered question is: How important is fresh air to this mostly closed system? I think I could run some perforated 2″ PVC through the box with open ends outside the box but it will certainly be more of a challenge to keep the system warm while also bringing in cold air.
    I don’t expect that I should open the box more than once a month. Am I on the right track???

    Any ideas or advice? I greatly appreciate anything you can teach me.

    Thanks. Sam

    • Hi, Sam. I’m glad you are thinking ahead! It is entirely possible that you could insulate this box well enough to keep your worm herd safe, but I definitely suggest burying the entire thing if possible and adding a warming element as well. Keep in mind that each time you open the box any “warm” air will escape and be replaced by 20F air (or lower) that will only chill your worms unless something is there to warm it back up. How much airspace were you thinking of having over the worms? If you could bury your box a foot underground and layer straw over the top, there could be plenty of air to access. However, at such low temperatures, your worms will not be crawling around to get to it. Perhaps it’s best to aerate your worm compost/bedding by mixing in materials that will create and keep plenty of airspace throughout the mixture all winter long. Like what? Straw, corrugated cardboard, non-matted leaf mulch, corn husks, wood chips (not cedar). Many of our members successfully overwinter their worm herds using creative techniques I haven’t even mentioned! I’d love to hear other ideas too!

  5. Thank you Francesca – Though I won’t be able to bury my box I will certainly be able to keep some aerating compost mixed in, add a heating pad, and lots of – surround the box – insulation. I’m thinking of a deep (2″ to 3″) insulated lid with several inches of space above the soil.

    So you think – no need for incoming air other than opening the box once a week – briefly?

    Started to realize too – that I should provide for a secondary bottom space for collecting worm castings. All this to keep my soil viable and the worms happy and active, LOL.

    Let the fun commence. Yes, please, I welcomely and all advice.

  6. Kathy Echevarria January 6, 2020 @ 1:01 pm

    In Florida it is 48 degrees outside this morning. I put my new worm set up in the garage yesterday and this morning put a glass bottle full of hot water on newspapers in side of the worm bed. Do you have knowledge of heating pad use over the top of the bin. I am looking forward to having worm castings.

    • Kathy, it sounds like you are taking great care of your worms. Good question about top heating. Most heating elements are set below because heat naturally rises. A heating element over the top of your worms would be a really inefficient way to regulate their temperature. You can rest assured that once you have a well-established worm farm, the temperature will more naturally maintain an average of the day’s high and low. That means in a bin of large area and volume, a warm day followed by a cool night will become less of a danger.

  7. I love all these suggestions! Do you think having the bins inside wood chip piles all winter our lowest is around 17 degrees. Or bury them in the soil and cover with wood chips. We have huge piles of wood chips we could bury them in. 2nd question. Can I feed my worms horehound weeds? they are in the mint family.


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