In a 7 mths old home. Odor which smells like a hamper full of wet, musty towels that have been left for a month in bathroom on rainy, damp, and cold mornings. Methane gas meter measured methane gas over stand up shower and toilet area - bldg. inspec. blew this off as a fluck. Peppermint test conducted by bldg. inspec. did not indicate a vent leak - I think this was because the vent stacks on the roof were not capped during the testing (inspec said they did not need to be) - should they have been capped. A flapper was placed on the outside sewer line to prevent sewer gasses from coming back into house, can gasses still get back into home through vent stacks or peat traps? What could this smell be?