that is an idea, but how would you keep it cool through the day? That is where a thermostat would come in handy and then you could set another to come on with a timer to cool it down further at night. As you can see you can go as simple or as complex as you want. The timer on a fan is not a bad idea, but it would not have that great of temp regulation during the night. You could actually get it too cold then if you think about it. A freezer when up and running gets down bellow freezing, and if you insulate your chamber well enough you could get it colder than freezing and that is even a little too cold for villosa.
So in reality it gets down to the fact of how complex do you want to take it. You can go as complex or as crude as you want. You have to decide.