I ferment using a freezer set to a temperature typically 6º F cooler than my target fermentation temperature. This has never ceased to get me within 2º of my target fermentation temperature. However, I pretty exclusively brew ales, and mostly all using the same 4-5 American and British yeast strains (Chico, Pacman, BRY-97, S-04, and 1968). I tried my hand at a pale lager for the first time in a decade of brewing (5.5 gallons with S-189, 5.5 gallons with MJ Bohemian Lager) and got active fermentation rolling at just 2º warmer than my ambient temperature. This means I am 4º below my target temperature of 52º F. I adjusted the temp control to let it get a few degrees warmer, but I am wondering if lager yeasts tend to produce less heat during fermentation than ale yeasts do. Does anyone have experience with this?
Not necessarily specific to lager strains. At lower temperatures, the yeast are less active, so they produce less heat.
I do ambient as well but only use a 4F buffer (never measured actual temps). I use more expressive british ale strains so I look at it as a plus if it is a little warmer. I don’t consider every xmbt as fact but last lager I did a NGP I used 3470 at my standard ale temps 64F and it worked so well I have no desire to fool with traditional lager temps nor a starter.
I would expect the exothermic action of a saison strain to generate more heat than normal ale. When I kill the tstat at high krausen I see near 80F.
An update: While I had a substantial lag (I understand this is common with these strains), there was some visible fermentation at 48F when the chamber was set to 46F. I increased the ambient temperature of the fermentation chamber to 48F and found fermentation going actively at 54F the next day. I suppose the slower start was what lead to the decreased temperature initially. I let it ride with the ambient temp set to 48F. I was planning to let it finish, then raise to ~70F for a day or two before crashing to 30F, racking into 5 gal carboys (I don’t trust my 8 gal buckets for long-term storage), and lagering it until mid-August.
If you’re raising the temperature at the end for a d-rest, I think 60 would be fine. No need to bring it up to 70.