Is this a mold contamination problem only in the winter?....if so you need to keep the space vented to keep the moisture levels down.
thank you i ll have it in my mind
Jimmys, As KMS said, if its an issue in the winter when the mold appears, its not only condensation that is occurring causing the issue. I am assuming the issue is with the ceiling? If so, check to see if its properly insulated. Poorly installed, missing or not enough insulation will allow even the slightest amount of moisture to condense on the surface of the ceiling causing mold and stains. If the ceiling is on a lower level and there is another floor above, you need to check the rim joist area that is between the ceiling and the floor above. Quite often then not there is no or very little insulation located in this space. This allows cold air to cool down the ceiling and cause the condensation to form. So even with the best attention to new paint, even microbial types, if you do not correct the reason why you have moisture condensation the mold will return.