I brewed a Two-Hearted clone last Saturday. I had a difficult time keeping my fermenting room in the basement up to proper temperature during the week when it was 0-5 degrees for 4 straight days. I pitched White Labs 001 yeast, and the fermentation was pretty active Monday and into Tuesday. By Wednesday, it had slowed down (which isn’t uncommon in some cases), but I noticed that the temperature of the fermenting beer had dropped to about 60 degrees. I brewed a Pliny the Elder clone yesterday and wanted find a way to get the temp back up in that room (old bathroom so it’s small). So I put a halogen spot light in the room for a bit. It did a nice job raising the temperature to about 67-68 degrees. The Two-Hearted became active again, which I am happy about. How, if at all, will this affect the taste of the beer?
The beer will be fine from the temporary cooldown. You didn’t mention what kind of fermenter, but you don’t want a spotlight shining on a hoppy beer. It will get skunky. I put dark T-shirts over my carboys if their not in a dark room. Buckets don’t have that issue.
Coolness around 60 F is actually a good thing for most ales IMHO. I would have let both batches go at 60 F. They will turn out great. Just takes an extra day or three to ferment on average, that’s all.