Well the leaves are changing, the days are shortening, and the crispness of the autumn air signals the onset of a winter that climatologists fret will be harsh. So what do we do? We insulate our homes, stock up on non-perishables, make sure our children are kept safe from frostbite with clothing to protect them from the elements.
But let’s not forget the important things.
Like ensuring our composting earthworms survive the winter.
For those of us with worm bins outside the comforts of our homes, winter is a source of worry and a test of confidence. How will they fare? Will they thrive, survive, or freeze to death? Windrows, more commonly used for vermiculture rather than vermicomposting, are insulated with layer upon layer of straw, which normally keep a core temperature high enough to continue growth and reproduction. But most home worm composters want easier year-round access to the worms so they can, you know, compost with them. This is definitely the case with me.
What Do We Do?
So how do we keep both the worms and our spouses (who may not want the wigglers inside) happy?
To be sure, there are a ton of ways to warm your worms while they’re outdoors, to include copious amount of straw, or consistent feeding to create some heat from the thermophilic or hot phase of conventional composting. Other ideas include soil warming blankets, electric heating elements inside containers of water inside the bins or water circulating systems with flexible piping.
Done correctly, any one of the above techniques would do the trick, but none seemed to suit my needs.
I found heating blankets to be too expensive and the reviews weren’t the best. And installing a water-based heating system seemed cumbersome and a little expensive as well since I owned none of the equipment needed to make them. I wanted a lightweight, inexpensive solution that could be easily removed from the beds for feeding two things: the worms and my worm-stalking problem.
For my small worm growing operation, I use horse stalls with two-foot wide by 11-foot long beds with cinder block walls. Thankfully, the beds are slightly below-grade, which offers ambient natural heat from the warmer ground. But the winters in Pennsylvania require a bit more than that, especially if I want to keep the Red Wigglers at 70F or higher to facilitate max baby making.
So after stumbling upon a makeshift soil heating system using plywood, one-inch strips, and rope lighting, I thought I would try a variation on that using a more moisture-proof surface than plywood to accommodate the rope lighting. And rigid foam insulation board was the ticket.
The Urban Worm Warming Board is Born
I picked up one 4ft x 8ft R25 insulation board from Lowe’s, which I then cut in half lengthwise to fit my beds. (R value is a measure of thermal resistance and the higher the value, the higher the insulation potential. The rolled insulation in most American homes is about R13, so this is pretty good stuff.) I also ordered two rolls of 30-ft long incandescent rope lighting. While the more modern LED rope lighting is cooler, and therefore more energy efficient, I actually wanted inefficiency since the worms would be warmed by the discharged heat of the incandescent lighting. To maintain a flattish surface underneath and to more evenly disperse the heat, I routed serpentine channels in the foam board to accommodate the rope lighting. For a quick walkthrough, see the slider below.
You Can Adapt This To Small Spaces Too
One thing I like about using foam insulation boards is that they are adaptable to any shape you’d like as the insulation is very easily to cut, even with a hand saw. The only tool I used with any sophistication was the router, but a patient person with a steady hand could use a simple carpenter’s knife could make themselves a nice channel to tuck the rope lighting into. With some minor modifications to a Rubbermaid bin or other homemade worm containers like a 5-gallon bucket, you could make a cozy environment for your worms fairly easily.
This Seems Great And All But . . .
While I’m excited to see how this worm warming board works, it’s not time to pat myself on the back too vigorously. I still have some concerns:
First, I am worried whether it will tend to overheat or dry out the upper couple of inches of the bedding and food, which is where Red Wigglers tend to reside. I have a few workarounds in mind:
- Place a layer of cardboard between the warming board and the bedding/food. But I’m not thrilled about the idea of introducing a possible fire hazard to my worms or my barn.
- Place a dimmer between the warming board and the power supply, which will help control the amount of heat produced by the lighting.
- Prop the warming board a couple inches above the bedding/food. But any time the lights are powered, I can’t really count on the worms to do much eating as they’ll be more interested in escaping the light, which will now be visible to all worms under the board.
- Install a soil thermostat in one of the beds to make sure the environment never gets too hot or too cold.
- Install a timer to provide enough heat every day to ensure my beds won’t freeze at the very least.
Secondly, how cost-efficient will this be? Might I be better off giving the worms a good feeding and a new batch of dual-purpose aged horse manure before resolving not to bother them for a couple weeks at a time throughout the winter? Might the cost savings of foregoing a heat source in a very drafty shelter outweigh a (hopefully) moderate slowdown in reproduction and vermicomposting efficiency? My electric bills will tell the tale!
Thirdly, my beds are 11 feet long while the worm warming boards are 8 feet long. I either need to shorten the beds or leave them the way they are and have about 3 feet exposed to the elements. In the event the boards start overheating the bed surface, this might give the worms and escape of sorts to cooler areas.
We’ll see what kind of results I’ll get. I’m excited to have a solution that may be both effective and easy to remove. When I started this hobby a couple years ago, I was quickly surprised at the wide range of conditions that the worms, especially the Red Wigglers, could still thrive in. While I worry simultaneously that I will freeze AND burn my worms, something tells me this will go just fine. I’ll post an update in mid-January to let you know. If you’d like to be notified when I post this update and get an immediate 10% store-wide discount to boot, sign up for the Urban Worm e-mail list on the top of the home page!
Till next time, Worm On.
The 2019 Vermicomposter's Starter Guide
Your roadmap to a successful beginning in vermicomposting.