#15 Felt provides a extra moisture barrier to wind blown rain. #15 felt has a permeability. #15 roof felt consist of recycled paper and asphalt.
Highlights
#15 Felt type construction helps provide an extra layer of protection between your shingles and your roof deck (not included)
Heavy-duty design lays flat to help minimize wrinkling
Asphalt saturation to help improve waterproofing ability to help prevent wind-driven rain and water from other sources from infiltrating under your shingles and causing damage to your roof structure or the inside of your home
Slip-resistance for safety in warm climates
Accurate lay lines help provide easy, consistent shingle application