Why don't you just close yourself in a wardrobe and after having night vision see eventual light leaks and stop them. I did so for many years when I was loading 100ft film to film canisters. Always glad to leave for fresh air.
It's not for nothing that normal tents used in nature have huge air flaps for air flow. And even so, in a cold morning you will find its walls wet from your breath.
Heck, close yourself to a wardrobe and see for yourself how you like it. No need to ask anybody else.
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