We had cedar siding placed on our home 8 years ago and within 6 months the beautiful white surface began turning black. After years of consultations and research we discovered that this was environmental mold. We initially cleansed the stain with mildicide and restained with return of the mold within months. We attempted to remove the stain and use mildicide followed by additional application of stain with no luck. We now have replaced the siding at great expense in hopes that we can control the growth. We plan on washing the stain yearly with a mildicide and restain every 3-5 years. Any additional suggestions? Could this have been caused by poor wood preparation or improperly dried wood initially? Thanks.