Have you read the articles about dormancy on this site?
http://www.flytrapcare.com/venus-fly-tr ... -faqs.html
As you say, a dark, damp environment is the perfect recipe for fungus, mold and rot. On the care sheet that comes with every flytrap purchased here, it says, "For Venus flytraps, being soggy wet and cold is unhealthy (just like it is for people) and can cause fungal infections, rot and even death."
http://www.flytrapcare.com/store/venus- ... care-sheet
Instead, try to think about where flytraps grow in the wild... In the wintertime, the sun does sink lower in the sky and becomes weaker, but it never goes away completely and they still receive at least 8 hours of sunlight each day. At night, the temperature drops down *near* freezing, but not below it. Those are the conditions to simulate for what a flytrap needs during the winter so it can rest for a few months before starting to grow again in the spring.