Vapor permeability and SRI for unvented roof?
Building a new home, Climate Zone 5. Roof will be Uvented. Underside of rafters will be insulated with closed cell spray foam R-49 which will serve as A/V barrier also. Roofing is asphalt shingles. Most of roof is 12:12 cathedral with 5:12 dormers, with some minor attic area that will contain A/C ductwork. Overhangs are 16″.
1.Since my roof sheathing cannot dry to the interior I am seeking a vapor permeable self-adhered product to use at the eaves where I would normally use Ice & Water Shield, 6 ft up the slope. (The field of the roof is a typical vapor permeable underlayment). I am having trouble locating such a product…suggestions?
2. Would you recommend a higher Solar Reflectance for the shingles to reduce surface temperature of roofing & sheathing? (The best I can get for the aesthetic I want is SRI 28 so not terribly high)
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