Several months ago my house had a flood behind the wall. I had it professionally repaired with dehumidifiers and they cut out and replaced the wet drywall. They also replaced the flooring. A couple months ago I started to smell something mildewy or moldy. I've been away on trips and the house has been closed up a lot. I was becoming concerned that the dry out job didn't work. However, the weather has gotten colder, so I turned on the heat last week (gas heat). Now after a couple days the smell has vanished. Does anyone have any ideas what could have caused the problem.