I used thick foam insulation for my window and taped all around it, it's almost as insulated as a wall! I also keep my lights on during the day and use a night light at night, it's actually the LED from my converted beverage cooler that is the night light. I have my rats and mice in the same room so I want them to be able to see their babies so they can take care of them. I also feel it's beneficial for snakes to be able to see during the day time. I wonder if complete darkness would mess up their breeding? I turn the light on in the AM and turn it off in the PM leaving the night light on at night. My room lights are actually two 60 watt equivalent LED bulbs. LEDs take very little electricity to run all day long.