Building A DIY Warming Cabinet.

I’ve felt the need for a warming cabinet a few times in the last year or so. A late batch of cider failed to get started in the cold weather, and a warming cabinet, or warming pad, would have stopped the cider from ‘hanging’ and eventually being spoilt. Last Autumn I wanted to experiment with making biofertilisers, but many of them need some warmth to ferment properly. Again, a warming cabinet would have allowed me to experiment with the biofertilser. Finally, I have just bought some mushroom spawn, to grow edible mushrooms. They too need some warmth, so I finally got a grip of myself, and made one.

A quick disclaimer here. I didn’t bother looking to see how other people have made their own warming cabinets, I just knocked this one up. Please don’t copy this unless you can’t find anything better.

 DIY Warming Cabinet. The Start.

I had been considering building this warming cabinet for some time, and had actually made a start on it late last year, but had been distracted. I wanted to make the warming cabinet using mostly materials that I had that were not being used. The site that I chose was in an outbuilding. The house would have been warmer, but the smell of rotting fish (biofertilzer: fish hydrolysate) would not have gone down well….. I had previously constructed a large rack on which to stack unused beehives. The shelves were large, in order to accomodate a lot of hives, so I decided to repurpose one level to use for my warming Cabinet.

warming cabinet

Corner shelf unit used to make a warming cabinet

One useful benefit of this building is that we had used it to breed greyhounds in about 13 years ago. So I had insulated the wooden building with four inches of insulation, and then lined the inside. This meant that my new warming cabinet would not be leaking heat to the outside. The rest of the construction was really all about providing, regulating, and then maintaining heat.

5 gallon fermenter in warming cabinet

A 5 gallon Fermenter in Warming cabinet.

The picture below gives an idea of how big this warming cabinet will be. It shows a 5 gallon plastic fermenting vessel sat in the warming cabinet. It should hold at least 6 of these if I want it to. Cider anybody?

The picture also shows the first part of insulating the warming cabinet. The shelves are 12mm plywood, which wouldn’t be great for retaining heat. Luckily I had a roll and oddments of the silver foil insulation that I had used in my loft. It looks like bubble wrap sandwiched between thick foil. I just stapled it to the underside of the top shelf, and on top of the bottom one.

I cut the side panels from some old 19mm birch ply. Again, it was left over from another job. I had enough of the metallic insulation to do the sides, and a little left to partially cover the doors.

Wiring for the new Warming Cabinet

Wiring for the new Warming Cabinet

The picture above shows my failed plan to insulate the back walls. Despite knowing that the outer walls were going to be warm enough, I thought that I would try a layer of Aluminium foil (normal kitchen stuff) stapled on top of bubble wrap. I thought that this would give me a surface that would be easier to keep clean. Sadly the foil was too thin and kept ripping where I used staples, leaving the bubble wrap. Were I to do this again, and ran out of the proper foil, I would use gloss paint instead. The picture also shows the electrical cable and socket base for the power supply. It should be a socket capable of dealing with high humidity, but I didn’t have any available. I will replace it the next time that I pass somewhere selling them at a reasonable price.

Heating and Temperature Control

The picture below shows the two methods that I can use to heat my warming cabinet.

Warming Cabinet heating

Two methods for heating the Warming Cabinet

The white tube at the back is a greenhouse heater. It’s one of only two things that I had to buy. I bought it on ebay. The red pad on the bottom is a heat pad. I bought it to use to keep our pups warm. Unfortunately it doesn’t have it’s own thermostat, and neither does the green house heater, so I bought a plug in thermostat. Mine was a bit cheaper than the one in the link, but it works in the same way. Once the temperature that you set is reached, the plug socket is switched off, turning off anything plugged into that socket.

My plan is to use the two heating methods for different purposes. The current socket is for use with the greenhouse heater, and used for mushrooms, and anything else that doesn’t need direct heat. The heatpad will be for fermenting liquids, which can be stood directly on top of it. I’m not sure how effective the air thermostat will be for that, but I have a thermostat used with soil warming cables, and I may be able to tape the probe from that to the outside of one of the vessels.

Finishing Touches

The last job was to make some doors. I had wanted a way to use some perspex sheets, inside of the doors, but it was starting to make the job a bit complicated, so I gathered up a selection of old hinges and bolts. Luckily, when I offered up the first door to check the cutting, I saw that the wood could slide in and out rather that be hinged. This saved a lot of messing around, so I cut the second to size, and used a couple of screws to keep the doors in place when they are slid backwards and forwards. The picture below shows the doors partly open. You can see that i have used two different materials for the doors, ply and OSB, because that’s what I had available. It would have looked nicer to use the same material, but not if it meant spending more money.

warming cabinet doors

Sliding doors on warming cabinet

The Picture below shows the doors shut. The inside should stay warm and dark.

warming cabinet finished

The finished warming cabinet

There are still a couple of small jobs to do before the warming cabinet is finished. The doors need some handles. I’ll look for something cheap if I can. if not I’ll use some scrap wood. I also need to wire the plug socket. I decided to wait, as I’m out tomorrow, and if I can find a cheap socket that will be better in a humid environment, I’ll get it. Otherwise it’s a quick job to do, and will be finished tomorrow.


Overall I’m delighted with my warming cabinet. Using materials that I had available has kept the cost to below £30, with only a better plug socket still to purchase. The insulation should reduce the amount of energy that it uses to operate, and it has been easy to make, using the existing shelving that I had previously built. I still need to wire it up and test it, but that should be realtively easy to do. Most importantly, I can now get my mushroom spawn started off, and then begin making some biofertizers ready for Spring.







7 thoughts on “Building A DIY Warming Cabinet.

  1. Deborah Lacey

    Deano looks like sterling work. We made a warming cabinet from a ‘dead’ fridge. Took out all the cooling bits and stuck a 40W light bulb in it at the bottom of the fridge through the ‘sticky up’ (technical term 🙂 that) bit at the back. It was very efficient at warming 2x 30ibs buckets of honey to the required temperature for processin in roughly 48 hours, needed stirring before we went to bed and again in the morning and the buckets needed swapping from top to bottom position as one was warmer than the other. Yours looks quite a lots bigger though? That silver foil is amazing stuff…unfortunately a bit heavy on plastic. I wonder if you could use some other insulation instead of plastic? Like…er sheeps wool (too thic?k) or lots of carboard or…? I wonder if a dead freezer would work as well, that would give you more space than a fridge. Before anybody asks no I done think I have any pictures of it. It is not used any more and has gone to a new home!! Thanks for the seeds that Nigel came back with from the weekend BTW.

    1. Deano Martin Post author

      Hi Deb
      I would have tried a large chest Freezer if I had one to hand, but this gives me the ability to look into the warming cabinet easily. I had the insulation to hand, and don’t get too ‘stuck’ looking for ther perfect solution to everything. I find that leads me to paralysis, as everything has a potential downside. Besides, all that time that plastic stays in use, the carbon in it is locked up too.
      No woories about the seeds. Hopefully they’ll do good things for you. I’d be interested in how harvesting makes you feel? It made me feel very secure, knowing that all of that easily stored energy was sitting there.
      Take Care

  2. Andy

    The cider would have done well in a greenhouse or poly tunnel. The temp may have still been a bit low but almost certainly enough to start and keep going slowly. My greenhouse has hit 17 degrees and barely dropped below 10 in the last month bar the odd night.

    The frosty couple of mornings we had in the last week showed how well a manure heap keeps warm…a bit of water pipe in the heap and a pump going into a box could be another solution. Perhaps piped warm water around a 5 gallon bucket.

    …having said that a 5 gallon bucket, or several, of cider in the living room is never out of place 🙂 Sit and smell it, listen too it and dream about it 🙂

    A failed brew can often be reclaimed by scooping off any scum from the top and re-introducing some started yeast that is already going strongly – done that before without problems.

    1. Deano Martin Post author

      Thanks for the tip Andy
      Not being the key decision maker for what is allowed in the house is a potential problem, but trying to get a brew going again sounds like a great idea.

  3. John

    1. Thanks for this and for the link to the plugNplay temp controller… too easy. I had thought to design and build these myself in Oz, as we have nothing similar. Timers etc, but zero plug-in ‘thermostats’.
    2. Just a thought: wouldn’t a simple submersible aquarium heater provide the same service for heating a bucket and contents, plus maybe an aerator to provide the agitation/stirring. You may not want oxygen, but that could be excluded/limited with well-fitting lid. Insulation could be via any sort of blanket and sit the bucket and insulation (and wiring) into a larger bucket.
    3. Can anyone supply a link to true temperature control. (For an insectary.) I need to maintain a cabinet and eggs at around 20 deg C. My local ambient temps can be as low as 5-15 deg. at nights and; 30-40 deg. in the day (depending on season). A plugNplay would be great- something that turns on a heater when it’s cold and a cooler when it’s warm. And ‘intelligent’ enough not to have both circuits on at the same time. I hope somebody can advize. Cheers. JA in the Antipodes.

    1. Deano Martin Post author

      Hi John
      I thought that I had replied to your comment, but it doesn’t seem to have worked.
      The downside for an aquarium heater would be that it would only work on one container at a time. the cabinet will fit loads of different things in. Mine has 6 bags of mushrooms growing, plus the fish hydrolysate, and some germinating seeds.
      Not sure of the best option for your insectary. There are some greenhouse fan heaters that can heat or ventilate, but I’ve not tried them, so cannot tell if they would be suitable.
      All of the best

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