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.
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.
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.
I also did 20L batches when I was brewing. My setup was in my basement which while not actively temperature controlled did tend to maintain a fairly consistent temperature throughout the day and night. That baseline would trend close to 13C in the winter and may as warm as 21C in the summer. You may not need a lot of thermal stabilization depending on how responsive the temperature in your brew house is to the outside air.
The other thing to consider is that the temperature control is most critical during primary fermentation when the yeast are most active. As long as the temperature is maintained to their tolerance, and the whole vessel is neither rapidly heated or cooled then whatever off flavors they produce in primary fermentation they will tend to clean io during secondary, where you can even be more sloppy with your temperature. Even beers brewed with ale yeast benefit from a long secondary rest, and can produce some very clean profiles without strict temperature control.
In the end, it all depends on the kind of beer you want to produce. If you're looking for consistency batch to batch, then you'll definitely was t to control for as many variables as you can including temperature, water chemistry, strike and crash temps, your grains age, grind and whatnot. On the other hand if you're OK with some variability between batches of the same recipe and you take good notes on the process you can start to account for what factors contributed to different elements in the profile. (E.g., low ABV because it was too cold, or popcorn & bubblegum notes from too warm or too short a secondary)
For my own batches I tended not to control for temperatures during primary very much, other than to make sure I kept it within the acceptable range for the yeast I was using. I also tended to get busy and either not get around to bottling/kegging very quickly (or just forget) and so my beers tended to have that longer secondary fermentation I mentioned. (To be clear, it all just sat in the fermenter on the yeast cake for a week or three before I'd rack it off and either bottle or keg it. Didn't move it to a second fermentation vessel or anything.)
Time heals many of the woes of the home brewer. Another week rarely hurts. Just don't let it autolyze.
Anyway, I was always very happy with what I made, and I was tended to stick close to the reference styles. I usually received some great feedback from friends and family on my stuff. The guys at the beer club were less kind because, well, I'm in the US and if your beer doesn't have an oil slick and taste like dish soap because of the pounds of hops they like to use in every batch then they kinda dump on you for it.