Ferm closet cooling feasibility

I've been toying with the idea of converting my brew equipment storage closet to a fermentation closet for a little bit. I would insulate with 1 to 1.5" rigid pink foam floor to ceiling, seal off the door as best as possible, and whatever else needs to be done.

My question is about the cooling device - I have a mini-fridge available that's not being used, but I wonder if it has the umph to keep the room at a stable temp during hot summer days. The hottest I'll let my house get without turning on the house-wide A/C is about 80*F, and due to lack of ventilation in the closet, right now it can get a few degrees hotter in there, let's say 84*F.

Do you think that it would be capable of cooling and maintaining ~66*F temps through summer? Otherwise I'll start looking at your typical window-mount A/C units but I'd like to conserve the money and/or electricity if possible. If I have to invest in a window A/C I'll probably wait until it starts to get cold and see if I can nab one on clearance or craigslist or something.

Edit: more details about the closet. It's approx. 4' x 4' x 6' (shaped really funny) and one wall is against an exterior wall of the house. The door is a normal size (maybe 28"x72"?), hollow core piece of junk. No windows. I would like to put up insulation without any additional framing or really permanent attachments in the event that I need to remove it. I'd be flexible on the type of insulation and would rather spend money there than on cooling units & electricity.

I think it could work. I use a very small mini fridge, the cube shaped one that would hold about two sixers, and it keeps my ferm box at 60F with no problems. The ferm box is about 3 feet tall, 2 feet deep, 4 feet wide, (can hold 6 carboys), and (poorly) insulated with 1.5" styrofoam on top and sides. Back is pink insulation batting as it backs up against my basement wall, floor is basement concrete.

What is the plan exactly? Insulating the room then throwing a mini-fridge in there with the door propped open? If so, that isn't going to work. Refrigerators work by pulling heat from the inside of the mini-fridge box and dissipated the heat through the coils located on the outside. If the whole thing is located inside of a room then you aren't moving the heat anywhere.

For this to work, you need to orient the mini-fridge so the inside of the fridge faces the space you want to cool, and the coils are oriented into another space (outside, another room etc). You are then transferring the heat from inside to outside.

Make sense?

broadbill said:

What is the plan exactly? Insulating the room then throwing a mini-fridge in there with the door propped open? If so, that isn't going to work. Refrigerators work by pulling heat from the inside of the mini-fridge box and dissipated the heat through the coils located on the outside. If the whole thing is located inside of a room then you aren't moving the heat anywhere.

For this to work, you need to orient the mini-fridge so the inside of the fridge faces the space you want to cool, and the coils are oriented into another space (outside, another room etc). You are then transferring the heat from inside to outside.

Make sense?

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Broadbill's right. Here's mine:



2 computer fans blow cold air into the big box where my carboys sit.

Yeah I realized that after posting. I am going to have to go back to the drawing board on this one, and see what I can accomplish with the space I have.

Got some space under my stairs that might make a good chamber...

Mike_A said:

Yeah I realized that after posting. I am going to have to go back to the drawing board on this one, and see what I can accomplish with the space I have.

Got some space under my stairs that might make a good chamber...

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Another nugget of advice FWIW:

I think custom made fermentation chambers are a great idea, but they often don't make sense when you take into account how much it costs in materials to make them. You might have some scrap materials on hand that will lower the cash outlay, but its still might not be economically feasible.

I'm not sure what you are thinking in terms of scale and/or craftsmanship, but I'd be sure to figure up the costs before buying and see if it isn't just easier to pick up a used freezer/refrigerator from Craigslist and a Ranco to control it with.

Well, I'd be looking to fit (6) 7gallon fermentation buckets inside the chamber, so I might be looking at two chest freezers depending on the size I'd find.

But it is a good idea. I will look into it. I'm taking my time planning this project, since my basement holds pretty decent fermentation temps through summer. I'm also not looking for more repeatability in my brews just yet, since I rarely even brew the same recipe twice. There's just too many options to settle myself on one variety of beer!

Mike_A said:

Well, I'd be looking to fit (6) 7gallon fermentation buckets inside the chamber, so I might be looking at two chest freezers depending on the size I'd find.

But it is a good idea. I will look into it. I'm taking my time planning this project, since my basement holds pretty decent fermentation temps through summer. I'm also not looking for more repeatability in my brews just yet, since I rarely even brew the same recipe twice. There's just too many options to settle myself on one variety of beer!

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Well you may want to consider a walk-in chamber of some sort (i.e. under the stair option.

You are brewing more than the average poster....10 gallons every weekend, right?

If you make a chamber it is ideal to locate the compressor outside otherwise you will be dumping hot air in house on hot days

broadbill said:

Well you may want to consider a walk-in chamber of some sort (i.e. under the stair option.

You are brewing more than the average poster....10 gallons every weekend, right?

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I brew 15 gallon batches and I'd like to at least be ABLE to do a batch every two weeks. I won't necessarily be doing that every other weekend, since I'm a busy guy. I'd split each batch into 3 buckets, and have one batch on primary while another can be on secondary. That's the ideal setup, anyhow.

Sorry but a walk-in is out of the question, my house is too small and the area under my stairs is far smaller than I think you're imagining (only about 3 feet high).

Is there any way to rig up a chest cooler so that the lid/door is on the front rather than the top, without messing up the compressor? My fermentation buckets have spigots at the bottom, which makes it nice and easy to take hydrometer readings and transfer. If they were sitting at the bottom of a chest cooler with the lid on top, the spigots would essentially be useless since I'd have to lift the entire bucket out of the chest to use the spigot.

Mike_A said:

I brew 15 gallon batches and I'd like to at least be ABLE to do a batch every two weeks. I won't necessarily be doing that every other weekend, since I'm a busy guy. I'd split each batch into 3 buckets, and have one batch on primary while another can be on secondary. That's the ideal setup, anyhow.

Sorry but a walk-in is out of the question, my house is too small and the area under my stairs is far smaller than I think you're imagining (only about 3 feet high).

Is there any way to rig up a chest cooler so that the lid/door is on the front rather than the top, without messing up the compressor? My fermentation buckets have spigots at the bottom, which makes it nice and easy to take hydrometer readings and transfer. If they were sitting at the bottom of a chest cooler with the lid on top, the spigots would essentially be useless since I'd have to lift the entire bucket out of the chest to use the spigot.

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I've seen posts where cabinets have been built 2-3 feet off of the ground which would work for what you want (pulling off samples from spigot). However, you are back to where to shelling out for expensive building materials.

If it were me, I'd probably go with a fridge/freezer just big enough to hold 15 gallons (3 buckets) and not worry about keeping two 15 gallons batches under temp control concurrently. If I was brewing every two weeks, I'd be cycling the batches in/out of the ferm. chamber every 2 weeks. After 2 weeks, the majority of fermenation has happened and you are probably good to leave that batch at ambient for how ever long you keep your beer in fermenters before packaging.

Sounds logical. If I don't need to control temps on all 6 fermenters then I'd also be saving money & energy by making a smaller chamber and running the cooling device (whatever it ends up being) less.

I'm going to be pricing out the building materials soon, to get a rough idea of what it would cost to put together myself. I honestly have a hard time believing that some 2x4's, insulation and plywood would really set me back all that far. But I also will have to price out used chest freezers - which I'm sure the price on those varies quite a bit by availability.

Mike_A said:

I honestly have a hard time believing that some 2x4's, insulation and plywood would really set me back all that far. But I also will have to price out used chest freezers - which I'm sure the price on those varies quite a bit by availability.

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Well, a sheet of plywood and a sheet of insulation will run you approx. $30-40 right there. Framing members aren't all that expensive, but it looks like from other DIY threads that a fair amount of spray foam insulation and liquid nails gets used in the building of these. Those go about 6-8 bucks a can and you'll need 2-3 of them. Maybe more. Probably another 20-30 bucks in fasteners, framing, and insulation/adhesive.

Another thing to think about it mold....The inside of the chamber should be lined with some of that water-resistant hardboard...you don't want mold to be getting on framing members and/or the foam board insulation. Probably another $15-20 for a sheet of that.

So you could probably be able to come in under the $100 limit if you don't have to buy a cooling unit. If you do have to buy one, I don't see how this could possibly DIY it for cheaper than buying a freezer/fridge off of CL, frankly.

Then there is the cost of your time to fab together a DIY version, versus rolling a used fridge into your garage and plugging it in.


The big advantage is that can DIY a chamber that fits your needs, a particular space. In your case, you might want to go the DIY route is you want to store 7 buckets at one time....you probably aren't going to find a CL deal with the capacity for that. What I'm saying is that is might cost you more in materials than you think it should!!

Good luck! I'm interested to hear what you figure out.

EDIT: I see you have a minifridge already...so you are good there...

On second thought: you may just want to go back to your original idea of converting that closet to ferm chamber. The framing is already there you wouldn't need the plywood and you could buy some rigid foam for insulation and be done with it.

You'll need to figure out where to orient the fridge though.

Yeah that's the difficult/impossible part. The compressor & exhaust for whatever cooling device I use needs to be outside of the chamber or closet. I don't want to be punching holes in the walls of the closet to vent it out, and building a chamber within the closet would probably cause the rest of the closet to get considerably warmer.

I'll do some pricing of building materials once I have a rough sketch of the chamber based on the space I want to put it in. Starting to lean towards a chamber small enough just to fit the primary fermenters, but I feel like I should do some more homework on the role of temperature control of secondary fermentation to make sure it's not necessary/beneficial.

I just finished a 2x3x5 ferm chamber cooled with an altered 5000 btu ac. I cooled it down to 26 last night during some initial testing. Still have some insulating to finish up, and I'm waiting on my eBay temp controller.

Mike_A said:

Yeah that's the difficult/impossible part. The compressor & exhaust for whatever cooling device I use needs to be outside of the chamber or closet. I don't want to be punching holes in the walls of the closet to vent it out, and building a chamber within the closet would probably cause the rest of the closet to get considerably warmer.

I'll do some pricing of building materials once I have a rough sketch of the chamber based on the space I want to put it in. Starting to lean towards a chamber small enough just to fit the primary fermenters, but I feel like I should do some more homework on the role of temperature control of secondary fermentation to make sure it's not necessary/beneficial.

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If using a mini-fridge, you can certainly arrange it so that the compressor/coils face into your house. That is how your food refrigerator is set up, right? Also, it won't run too much keeping things at 60-65 anyway.

Depending on the size of your closet, you can make an insulated box smaller than the dimensions of your closet and arrange the mini-fridge so that it is off to one side of the closet. Just be sure to give the compressor coils a little space for heat dissipation.

o4_srt, that sounds pretty awesome. If I can ask, what was your approximate cost to build? Do you have a thread going regarding the build? If not, start one up because I need to see some beer porn and would love any details you could provide.

broadbill, the closet I'd be looking to convert is a very odd shape, layout and location in my house. The door swings open at the top of the staircase, so I couldn't leave the door open. If I'm going to go the route of a custom-built chamber, I'll just stick it under the stairs where it will be out of the way, and keep the rest of that closet for storing brew supplies.

Mike_A said:

o4_srt, that sounds pretty awesome. If I can ask, what was your approximate cost to build? Do you have a thread going regarding the build? If not, start one up because I need to see some beer porn and would love any details you could provide.

broadbill, the closet I'd be looking to convert is a very odd shape, layout and location in my house. The door swings open at the top of the staircase, so I couldn't leave the door open. If I'm going to go the route of a custom-built chamber, I'll just stick it under the stairs where it will be out of the way, and keep the rest of that closet for storing brew supplies.

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No thread. Cost was a bit more than intended, insulation was $90. Spent another $44 on 4 sheets of 3/8" plywood, a good $20 on 2x4's, and another $10 on aluminum duct tape. Add in another $10-$20 for misc hardware, and I'm at roughly $175. I got the ac for free, and had some r-30 fiberglass insulation leftover from home renovations, so I added that to the ceiling and floor for good measure.

For the air conditioner, I had to remove the thermostat and fan speed switches. Then, I just tie the compressor and fan wires to hot. Compressor runs nonstop when plugged in, but this will be controlled by the temp controller currently en route from china.

Additionally, I have to finish insulating the doors and add the partition. The plan is to use half for lagering/cold crashing, the other half for ales. Another temp controller controlling a small 120 Vac fan will move cool air from the lagering chamber to the ale chamber.

Both sides are large enough for 2 6.5 gallon carboys.

It's nothin too fancy, just a big box in the garage, but it should get the job done, and it's sturdy enough to double as a work bench.