Had composit TT decking. Mold became severe and it was only 4 years old. TT offered a materials credit. Labor was expensive, but we had no choice since every remedy we tried was unsuccessful and the mold was worsening. Went with their XLM, all 100 % vinyl. No composite. So far, the deck is only 9 months old, we are satisfied. Very easy to clean. No mold or black spots.