Normal humidity levels do not appear to support mildew build up. Proper provision of vapor barriers will prevent the migration of interior moisture from migrating to a condensation point inside the bale wall. Grain crops which provide straw as a by product are grown in most states. Farmers are happy to find an additional market for straw which is frequently burned. Coordination is needed to obtain the correct density, moisture levels, dimensions and baling twine.
Straw bales burn like phone books.
Unless surrounded by a sustained heat and flame source, surface fibers flash burn but do not sustain flame. Tests have determined that plastered bale walls are more resistant to fire than conventional frame construction. The ASTM E-119 test gives a plastered straw bale wall a two hour fire rating. Care, however, must be taken during construction as loose straw does present a fire hazard. Assurance of structural stability is the overriding issue.