Originally Posted by greenhaze
Sitting it on the rug was a good move. Will the temp drop much overnight ? I usually ferment on the low side of the recommended temp. Remember the temp of the beer fermenting will be anywhere from 3 to 10 warmer than ambient air temperature, depending on who you talk to.
Correct, I shoot for about 62-65°F during the first/active stage of fermentation, realizing that the fermentation would be closer to 66-72° internally. Sometimes I go lower, it just depends on what I am attempting to accomplish.
But realize the ambient air temperature is not going to be the temperature of the fermenting beer. Fermentation is exothermic and generates heat. Your bare concrete floor will act as a heatsink and keep the beer cooler. Placing it on the carpet (or a towel, or off the floor) will prevent the cold surface from drawing the heat away from the fermenter.
Anyhow, you should be good. FWIW, when I invested in fermentation control, my beers were perceptibly better.