Day-afternoon temps have been in mid-60s; night temps in mid-40s. Shop is uninsulated, and currently at 58F, outside air temp, 53F. Supposedly, temps will hit 68F by this afternoon.
I have a side-by-side refr/freezer that holds 2 carboys, stacked, on the fridge side. I use a Johnson thermostat/controller to maintain ale/lager temps in Summer. Since temps are dropping at night, I'm thinking of hanging an incandescent (halogen, maybe?) light bulb inside to keep it warm. What watt bulb would you guess would suffice?