Originally Posted by Thanlin
It was my understanding that lager yeast needs the 50-60 range to ferment. And while I acknowledge that lagering in a secondary usually happens near freezing the closest I'm going to get to that is cracking my garage door open and hoping for even lower temps.
50 - 60 is the generally the optimum range, but it's not unheard of for it to work at lower temperatures, albeit a lot slower. If we assume you're fermenting at 42 F then the actual temperature inside will be at least a few degrees higher since the fermentation process generates heat, so I think you're safe there.
I don't think you should have any issues lagering at 40 F assuming you give it a while longer in the lagering phase than you would if you were lagering around freezing temps.