Hi,
I’m having a house built in Central Oregon (Zone 5b). 

The roof is a 2.5/12 sloped single pitch of 12″ SIP panel. We will be having standing seam metal roofing installed 

I’ve been discussing with the builder the plan for roofing underlayment, Ice and water shield requirements and a means to vent outward from the OSB.

I have concerns about the ability of the roof sheathing to dry. 

-According to the builder (and county inspector apparently) Ice and Water shield is required under the metal panel roofing. I can’t find this requirement either in IRC 2018 R905 or Oregon Structural Specialty Code (Chapter 15). 

-We discussed ensuring a vapor permeable underlayment would be used, I was assured it would be vapor permeable.
Today they installed Epilay Platinum as the underlayment. I can’t find information on the permeability of the Epilay, except in the “Code Compliance Research Report” that mentions under the condition of use (section 5.5)

“Attic Ventilation must me provided in accordance with the applicable Code since there are no requirements to evaluate vapor permeability of the underlayment.”

Does this mean it’s only designed to be used with a vented attic? And is inappropriate for an unvented roof assembly like ours?

My plan was to use “Solitex Mento 3000 connect” and a grid of battens under the standing seam metal roofing. But was told this is unnecessary and that there was enough space under the metal roof for the sheathing to ventilate.