My snake room has a window that is badly insulated. When it is 20 degrees outside it makes my snake room about 60-65 while the rest of the house is set at 70.

Here is what i did

The best thing you can do is buy a good space heater which has a digital setting to set the temp where you want it. The last thing you want to do is buy a cheaper one without this option. I got a ceramic heater at Walmart on sale for $80 (usually $100). Always read instructions on these as they can be a fire hazard if used improperly.

I also got a window insulation set (plastic and 2 sided tape) for around 5 bucks. Finish it off with a blow dryer.

The last thing I did was buy a good humidifier. It holds about 3 gallons . I configured the humidifier to keep the room at about 65% humidity. IMO this is a must have because space heaters really kill humidity.

I keep that room set to 75 which in turn keeps the cold end of my racks at around 80-82. Depending on your rack heat and tub setup this may be different for you.