From the website, bags are "breathable":
This 34.5" x 33" x 38.5" Type A Bulk Bag (FIBC) with an open top is ideal for storing and transporting dry goods for agriculture, landscaping, construction, and other industries. FIBC bulk bags are made from a thick, woven polypropylene with a UV enhanced finish. This bag holds approximately 1 cubic yard or up to 2,205 pounds of weight, and allows air and moisture to pass through the container.
Hoped to get upwards around 2 years ahead (plenty of time for drying) but brutal June/July heat stopped my splitting efforts cold! Figure around 4-5 cords ought to do it--we don't go through nearly as much as ya'll up north