Cleaning mildew on canvas

[RocktheCasbah]

We have a very new yurt and already we have a mildew problem. We're addressing the humidity issue (we live in the Pacific NW so it's a major concern), but once that's done I need to clean the mildew that has grown in the folds of the fabric where the rafters meet the fabric wall. We have 100% cotton canvas walls (Sunforger Marine Boat Shrunk) and they say to wash with soap and warm water but I really don't want this problem to get out of hand. We live in a rain forest where mold and fungus flourish!

Any advice on how to approach the cleanup is most most welcome!