I’m renovating a house in the Catskill Mountains of New York.  We originally planned to retain the existing roof.  But as the project progressed, I grew increasing leery of the assembly, which consisted of 4 generations of asphalt tile, topped with a PBR metal roof panel to boot, and all resting on 2×8 trusses 48″ o.c.!  I’m no structural engineer, but if you add seasonal snow load, that sure is a lot of weight for this type of framing!

We eventually made the call to strip the roof down to the trusses and start fresh with 2×4 purlins 16″ o.c. atop the trusses, then a layer of ZIP System roof sheathing that was fully wrapped with Grace Ice and Water Shield.  Hey, I can sleep better at night knowing that we cut a lot of that dead load.  

However, we then pivoted to a standing seam metal roof by Pac-Clad (040 material in a metallic/reflective silver finish).  My concern is that we used the standard Grace Ice and Water Shield, not the HT (High Temp) version.  Any opinions on if I can get away with this?  Having just rolled out about 3,500 SF of this product, I would sure hate to have to laminate it with an additional product.  I’m hoping that my selected roof finish (reflective zinc) will absorb less heat than a darker color, affording me some leeway on the underlayment.

Thank you all for any advice!