Hi Barnz,

If the noise emanating from the panels is indeed a sharp "cracking" then the likelihood of some critter being the sources is low to none...

These sounds are indicative (usually?) of two things (especially on roof:)

1. Age induced thermal expansion contraction cycles of the panels as they warm and cool.

2. Shear fracture of the attachment screws, which create a loud audible snap or crack when they do fail.

The later can become a cascade effect as more and more of the attachment hardware is compromised and lost...only leaving less of the screws to do more of the work. This is also indicative of a SIP company (or project facilitator/DIYer) that did not use the appropriate number of attachment screws to begin with.

Removing a roof and adding more hardware is one solution. Another I have seen is "cleating and bracking" systems added from the inside of a frame that does alter the aesthetic but can be performed in some cases not to be to invasive, or unpleasing.

I agree with Sean..."What does the installer and the SIP manufacture have to say?" I would be curious to understand there view, support and responsibility they would be willing to take in all this?

Good luck and keep us up to speed with your findings and solution...