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Passively regulating fermentation temperature (feddit.de)

submitted 5 months ago by Aarkon@feddit.de to c/homebrewing@sopuli.xyz

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Last time I brewed at home, I had my fermentation bucket in my flat, where the heating pretty much took care about all thermal regulation I needed back then. As I now have kids, I don't feel comfortable doing that anymore for various reasons.

I have freed up some space in my garage now for brewing & fermenting, but I have no heating there. I'm OK though to go with the seasons, brewing beer styles where the yeast's preferred temperature roughly matches the weather. But now, my mind is occupied with the question of how to keep the temperature as constant as possible for fermentation: While a weather forecast of e.g. 15°C doesn't sound too bad for lager beers, it may easily get as cold as 5° at night, giving the yeast probably a rather bad time. As I also don't want to spend a fortune on a temperature regulated fermenter, I'd like to even out those mins & maxes passively.
My thoughts so far circle around insulation (obviously) and thermal mass. Insulating the bucket itself seems like a nobrainer. But I think it also might work to build some cheap wooden enclosure, insulate that with Styrofoam, make everything somewhat airtight and add water bottles, rocks & bricks to fill up as much space as possible. That will of course do little should the weather change drastically, but so far, I think I'd stay way below max and above min temperature in there at all times. This way, I believe I could get a decent fermentation when the average outside temperature of night & day is right for a couple of days.

Is anybody here doing something like that or has experiences worth sharing otherwise?

P.S.: Addressing the elephant in the room: For now, fermenting under pressure is no road I want to go down. Buying a new fermenter, kegs, valves, fittings, hoses, CO2 bottles and either a counter pressure bottling system or even switching to drafting entirely is just too much right now.

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[–] solidgrue@lemmy.world 1 points 5 months ago (1 children)

The insulated box idea is how I used to do it when I was still brewing. In fact you don't even want it to be airtight because the fermentation both generates heat and offgasses CO2, both of which you will want to allow to escape to the outside.

Depending on your batch size you might only need a few bottles of water, maybe about 20% of your batch volume, to help stabilize temps inside the chamber.

Working your brew schedule to the prevailing temperature is a fun challenge, too. I enjoyed my winter lagers as much as my summer wheats. It felt like i was keeping old traditions alive.

[–] Aarkon@feddit.de 0 points 5 months ago

I didn’t mean airtight as in diver equipment, but you’re right in pointing this out because I didn’t say so. Of course there has to be a way for CO2 to escape, or I‘d be fermenting under pressure by accident.

My batch size is 20 Liters, maybe 25, I don‘t think I can do 30. What was yours? My gut tells me this is not enough thermal mass to sustain an even temperature when highs and lows spread out more than 10 °C or so.

From my last batch, I kept a few bottles for up to a year and it didn’t turn bad, so brewing with the seasons doesn’t even necessarily mean drinking with the seasons only. But yes, I like the thought as well that this is the way it has been done for centuries. Buying food in the same fashion isn’t something I always do, but it feels weird to me having fresh strawberries available all year long and I tend to avoid those.

[–] PlasticExistence@lemmy.world 0 points 5 months ago* (last edited 5 months ago) (1 children)

If you want no electronics in the mix at all, insulation is about your only option. Since fermentation is an exothermic process, you'll also want to make sure you can keep it from getting too hot. Your beer will taste a lot worse from the yeast getting too hot than it will from the yeast being too cool.

You can buy inexpensive temperature controllers, and if you can do simple wiring, it's not too hard to add a power outlet (and an enclosure). From there a fountain pump some tubing, a cooler full of water and either a heat source or a cold source can serve as a simple way to regulate your fermentor's temperature.

The heat source could be something like an aquarium heater or a sous vide heater and will sit in the cooler (always on, not run to the temperature controller). You'll tape the temperature controller's sensor against the outer wall of your fermentor (with some insulation taped over it. A paper towel folded a few times works fine), put the fountain pump in the bucket of water with the fermentor, and run the tubing into the cooler. The output of the tubing should be run back into the bucket.

When the fermentor gets too cool, the temperature controller will kick the fountain pump on which will take the water from the bucket and run it through the hot water in the cooler and back into the bucket. This will slowly raise the temperature inside the fermentor - and slow is what you want with yeast.

You can replace the heater with ice or frozen water bottles if you need it to cool your beer in the warmer months. I did this for a while before moving to using a chest freezer and reptile terrarium hear mats regulated by the same temperature controllers.

[–] Aarkon@feddit.de 0 points 5 months ago (1 children)

For me personally, this is less an issue of electronics (which I‘m sort of fond with), but rather of actively spending energy for a prolonged period of time, be it electric or fossile. Not only are energy prices way above US levels where I live, it also feels wasteful from an ecological standpoint. Especially so since there ways around it seem to exist. For that, I‘m willing to work with seasons and weather conditions.

Good hint though that yeast typically is more tolerant towards cold than towards heat. I didn’t consider this, but leaving a good amount of headroom on the upper end of the spectrum sounds like a good idea. That said: It‘s been pretty rare that the climate in northern Germany made cooling an issue outside of food conservation. But that may change in the future.

[–] drre@feddit.de 0 points 5 months ago (1 children)

i use aquarium heaters but never cared about the energy consumption. my experience is that since fermentation is exothermic they rarely kick in. especially with larger fermenters it's usually more important to prevent it from getting too hot. so maybe running larger batches might be something for you.

[–] Aarkon@feddit.de 0 points 5 months ago (1 children)

Energy consumption would be pretty much determined by the outside vs preferred temp-delta, so brewing heat loving Belgian beer in the dead of winter would make those heaters run all the time I suppose, even with serious insulation. Northern Germany‘s climate doesn’t make cooling an issue for anything else than food most of the year, but I’ll keep that in mind, thanks.

My batch size is limited by the size of my equipment, I can’t really go beyond 20, maybe 25 Liters.

[–] drre@feddit.de 0 points 5 months ago (1 children)

another option could be buying a thermobehälter like this one https://www.metro.de/marktplatz/product/c7cabb7a-c128-4217-b248-43ac62542742

i use something like this for mashing and rests as these a very temp stable and cleaning is a breeze. never used it for fermentation though. but one could easily drill a hole through the lid for the fermentation lock.

[–] Aarkon@feddit.de 0 points 5 months ago (1 children)

Nice idea, but I’d really miss an opportunity to drain the vessel without tubing.

[–] drre@feddit.de 0 points 5 months ago (2 children)

i use a false bottom, something like this

https://www.hobbybrauerversand.de/MattMill-false-bottom-357-mm

i also have this one (but never used it 🙄)

https://www.hobbybrauerversand.de/MattMill-Laeuterhexe-1000_1

[–] Aarkon@feddit.de 0 points 5 months ago (2 children)

Yeah, but how do you get the actual liquid out? The vessel doesn’t seem to feature a drain, so you’d need hosing for that.

[–] drre@feddit.de 0 points 5 months ago (1 children)

sorry didn't check the original picture. mine has a drain. can't remember where i bought it though. but it should be easy to install one. the metal is quite thin

[–] Aarkon@feddit.de 0 points 5 months ago

Ah Ok. 😄 Never dared to install one in the past, but now I have better tools. I’ll keep the possibility in mind!

[–] drre@feddit.de 0 points 5 months ago

sorry didn't check the original picture. mine has a drain. can't remember where i bought it though. but it should be easy to install one. the metal is quite thin

[–] Aarkon@feddit.de 0 points 5 months ago

Yeah, but how do you get the actual liquid out? The vessel doesn’t seem to feature a drain, so you’d need hosing for that if I’m not missing something.