Grace roof underlayments are excellent air and vapor barriers. Proper roof ventilation and insulation should be left to a qualified design professional and should comply with all local building codes. Standard roofing practice is to use 0.093 square meters (1 square foot) of net free ventilation area per 14 square meters (150 square feet) of attic space, split evenly between ridge and soffit vents. Grace roof underlayments are not intended for use as an air and vapor barrier in above-grade wall assemblies.