Gee, a few degrees?? So far all my mashes ( a big six) have lost a few degrees in 10 minutes or less. But Like I said the coastal influence here is strong. Might be better in the summer but highly unpredictable because of the fog that rolls in whenever it gets too nice or it will get windy. We have pretty unstable temps here day to day, hour to hour and minute to minute sometimes. I am sure with enough insulation temp swings could be made more stable but seems like six of one half dozen of another kind of deal.