I know there has already been few threads on mould, but our problem is somehow different - it smells terribly in the flat (it is a mould smell - not only in our opinion). The mould was visible on the floor last winter, but my partner removed it chemically and at the moment there is no visible sign of mould - but we are sure that the smell comes from inside the walls (not well isolated probably + ground floor). When the temperature falls below 0 C, all the windows are steamed (inside the flat) and the walls become humid. We air the flat 4-5 times a day (up to 50 minutes a day) in the winter, don't dry clothes inside ect. The landlord is however not bothered, after several e-mails and countless phone calls he finally sent us today a specialist to measure the temperature and humidity in the flat. In 3 weeks he will sent us the results and - the best part comes now - the landlord said that if there is a mould and it is caused by us (how???) we will have to pay for the flat renovation and cover expertise cost. At this point all that we want is to change the flat - we just cannot deal with the smell anymore - but we have a 3 months notice. This is obviously too long, but the landlord is decided to keep us here no metter what - she knows that it want be possible to find nachmieters (it smells to badly). The Mieterverband has advised to write a notice with a shorter period or to claim part of our rent back - but how can we actually "prove" the smell? Any ideas are welcome!!