I built a timber-frame in 2005 and attached a SIP roof and walls with long screws that extend all of the way through the panels and into the timbers.   Each screw has a large washer to keep the screw head from burying into the exterior OSB.  I assume this is the common way to attach SIPs to timber-frames (?).  A light snow is melting off of my roof and I can see a circle where each washer is, where the snow melted first.  I took a scrap of SIPs and pushed a screw through the foam, as the install crew did after penetrating the OSB.  The screw shank is not sealed by the SIP core because the screw threads create a hole that is larger than the shank.  I suspect that interior air is leaking through each screw hole and I am concerned that the exterior OSB will rot.  Does anyone have experience or advice on this?
Thanks