I had a new composite 20 year roof put on my condominum this summer. After the first big rains I noticed a leak. We also notice an 18 to 20 inches of mold growing at the joining of the ceiling and the wall. This was not at a hidden area it was above a window and 5 inches from the outside wall structure. An inspection of the roof and exterior of the building showed that the original ventilation holes drilled into the outside soffit, approximately 4 per every 18 inches, had been covered by louvered covers. These covers had the louvered opening flattined and appeared to seal most of the air off from under the roof. My question is could this "sealing " of the vent holes be the cause of the growth of the mold. It should be noted that a water test at the sight of the mold concluded that there was over 50% moisture. Please advise, Thanks Bob

i take it you are in a warmer climate and the soffits still need to be open to allow air to flow upwards into the attic space to a roof vent/turbine/whirlybird.
did the roofers also put roofing felt on the entire roof befor the shingles...guarentees a dry roof from wind driven rain getting up under the shingles and into the roof space.