Moisture management is the largest risk I know of with foam. Of course ideally the wood holding up your house or roof never gets wet, but if it does it's not an

Moisture management is the largest risk I know of with foam. Of course ideally the wood holding up your house or roof never gets wet, but if it does it's not an existential threat, unless it stays wet. Foam doesn't allow the wood to dry, and that can cause rot. Rot, if it's enough members can cause structural problems.