In the winter, my indoor temps drop to around 60-65 (especially at night). This leaves the tub cool side sitting at in the high 60s/low 70s.
The rack can maintain a 77-80 ambient with the door closed. It definitely doesn't drop below 75. I haven't had an RI yet.
I keep the door open during the day and non-winter months.
The actual purpose of the door was to keep away unwanted eyes and my ferrets out during their play time. But it turned out better than I expected for retaining heat. haha.