As I type, I'm boiling a couple of lagers. I typically pitch & ferment at 50F, either using my kegerator, or relying on winter to cool my basement to 48F-52F.
However, Portland is currently having a cold snap, and my basement is 40F. I suppose I can use hot water bottles in a water bath to raise the temp ~50F. Any other ideas for keeping lagers warmer than ambient?