We are designing a home in Santa Fe, NM with a sloped roof. The structural engineer is really pushing back on the idea of using insulation board here because he doesn’t know of a good rigid product to attach the metal roof to nor proper underlayment to use. Does anyone have a product recommendation or detail they could share to help us push for this? We’ll use spray foam in the roof cavity, but our energy models suggest that the rigid board is going to make a big impact since it provides a thermal break.