Paul, You’ll want to pull off cover plates and get remote moisture meter probes into the straw bales in as many places as possible. Once moisture gets into the straw it can be a bad scene, especially if the moisture has no avenue for escape.
I started researching inspecting straw bale homes after a client with Multiple Chimical Senitivity asked me to inspect one. There’s a lot of info on building them, but very little on inspecting them. Much of what’s written is romantacized.
Lot’s of opportunity for bad things to happen with those homes. Lots of liability in inspecting them. You need to disclaim the straw LOUDLY. Many homes leak eventually and with no other type of construction is it so important to avoid leakage. You need to point out to the client what can happen once mold gets going in that straw. A straw bale home with a flat roof is a bad thing, but achitects like to design them to look like southwestern adobes.
Also, the exteriors can be a problem. They used to use stucco-cement which, if it was allowed to freeze during installation… bad. You have to find an inconspicuous place and scrape away at it to determine the condition. If it’s all powdery… bad.
They now often use more high-tech exterior wall coverings but i’m not sure about them. I’d want to know before I accepted liabilty for the inspection.
Most of what I’ve discovered about how to inspect these homes has come from builders. Most of what’s online and in print paints glossy pictures and totally ignores potential problems. I’d charge a lot of money for the inspection and go through my disclaimers carefully beforehand and make sure the client understands the limitations. Mold can total these homes. At least that’s my take.