Closeup of one of our roofers nailing a shingle over the CedAir-mat ventilation matting we specified for this cedar roof located along the Connecticut River. We recommended using a ventilation mat for this installation due to the home being in a very shaded location in this moist environment - it provides a drying surface below the shingle but on top of the Ice and Water barrier to protect the shingles from the impact of moisture. In addition, we specified cedar shingles treated with cromated copper arsenate (an antifungal preservative).