Here's additional information from Joyce Coppinger of www.thelaststraw.org. (Thanks, Joyce.)

-Troy

Bale buildings in Nebraska have endured our climate and weather for over 100 years. One hay bale building built in the early 1900s here in Nebraska was never coated with plaster or stucco or any other exterior coating and it remained out on the Sandhills prairie of western Nebraska until just two or three years ago. The bales of straw do not have to be removed and replaced. In fact, it would be very difficult to do so, especially for load-bearing straw-bale structures. It would be the same as tearing down a stick-frame building just to reinsulate it. The straw really doesn't deteriorate within the walls, if it remains dry.

It is very important that the straw be dry when it is cut and baled, transported and stored, while being stacked and until it is coated. This will help prevent mold and mildew. The quality of design and construction work is another important factor in keeping the straw in good condition throughout the life of the house. An important factor in design and maintenance of any home is the attention given to natural ventilation and venting of the structure. This includes placement of windows and doors so that there will be good ventilation in every room and cross ventilation in both directions through the structure; vents in the roof and in the attic, and fans to move and/or remove heat, cold and humidity when it needs to be vented. While a house should be tight to avoid loss of heat or infiltration of cold air during times when heating and cooling needs are high, a "too tight" house will create problems of its own, including mold, mildew, poor indoor air quality, and insufficient fresh air.