Your situation there would be different than mine here. You have a much longer and more intense winter. Our winter typically goes cold snap for 2-3 days then back to 60-70 degrees with this cycle occurring several times.

I wouldn't call our sulcatta shelter indoor. It is out in their enclosure. They go in and out as they please. I think it is 10 x 15.

At you location they will need to be indoors for several months.
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CDieter
'Reason, observation, and experience; the holy trinity of science.'