Replacing Shingles on SIP roof – GreenBuildingAdvisor

My head is spinning from reading so much about SIP roof assemblies here on GBA, but I don’t have a direct answer to my specific questions. I’m hoping I can get them here so we can move forward. 

We live in a house in climate zone 6B (but bordering 7B per GBA’s climate zone map) built in 2005 that we purchased in 2017. SIP roof. SIP walls. The shingles in general are starting to wear out. It’s time to replace them. None of the roofers that quoted the job paid any special attention to the fact that the roof is SIP, so I’m the one going down rabbit holes to figure out what needs to happen. 

Our house is generally well sealed (tested at 1.98 ach50), but we definitely have a least some heat loss at the roof seams (see photo) in the winter. We installed a multisplit heat pump in 2021, and the lines run through the “attic” (a conditioned but unfinished space), which keeps that space warm and seems to have the worst heat loss, though we’ve tried to seal it up well from the inside (photo is pre-sealing). We have had one small leak through a beam at a north-facing valley where there was an ice damn (see photo of valley). I think I’m seeing some slight shingle ridging (or maybe I’m paranoid) above that attic space.

1. I’m terrified of what we’ll find under the shingles after reading so many horror stories. How prepared should I be for extensive OSB rot?

2. Let’s say the OSB is fine. Is there an acceptable assembly we can do WITHOUT adding a cold roof? We don’t have one now, and it’s obviously going to be a lot more expensive to add one during this process. We don’t have the budget for a metal roof, and are hoping to move out of this house in the next 3-5 years (but we want to “do right” by this house). 

3. Once the shingles are off, should we take the opportunity to seal the seams on the outside? We have been working on sealing on the inside.

4. I know some manufacturers void their warranty on unvented roofs. Which manufacturers will warranty unvented SIP roofs?