Sorry to hear about the loss of your colony. I hope you can figure out what happened so to prevent it in the future. Definitely post your discoveries here so we can all benefit. This Fall I too was checking on my bees daily by looking through the SBB. It's a great way see what's going on without opening the hive. But when it got to cold I closed it up for the Winter. Many beeks around here use the solid boards only. They say it allows the queens to lay their eggs down to the bottom of the frames in Feb, March, & April. Their hives are made up of a Medium on a Deep. Yet, I had condensation problems last Winter and solved it by installing a SBB. I use a Double Deep hive.