Using Stimw advice I went to the Tyvek website and found this:
DuPont™ RoofLiner
Premium roof underlayment
DuPont™ RoofLiner premium roof underlayment provides excellent protection against leaks under all types of roof coverings identified by ICC-ES AC48, Section 3.0*. It is trusted protection that can give both you— and homeowners—greater peace of mind.
Made with DuPont™ Elvaloy® AC copolymer
Ideal for sloped (≥2:12) commercial and residential roofs, new construction and re-roofing applications
Class “A” fire rating per ASTM E108
High UV-resistance with up to 6-months UV exposure per ASTMG154
Florida building code approval FL11602-R1
Miami Dade County approval [.pdf]
Approved for use in Canada. Meets Canadian CAN/CSA A220.1 code Intertek #3193611COQ-003A
Superior tear resistance compared to roofing felt for increased durability
Lightweight for easy handling and installation
Better coverage - one 10-square roll replaces about 5 rolls of 30-lb felt
More resistant to mold growth than roofing felt
30-year limited product replacement warranty for builders, general contractors and Professional installers.
Available in 2 sizes: 10-square roll and 4-square roll
» The 10-square roll is 48" x 250' (1.2m x 76.2m) and
contains 1,000ft2 of material (92.9m2)
» The 4-square roll is 48" x 100' (1.2m x 30.5m) and
contains 400ft2 of material (36.6m2)
Proven performance
DuPont™ RoofLiner is made with DuPont™ Elvaloy® AC copolymer, from the family of DuPont polymers used as the basis of the world’s best commercial roofing membranes. DuPont™ Elvaloy® is the brand leader with decades of proven performance in billions of square feet of commercial roofing worldwide.
One 10-square roll vs. 5 rolls
DuPont™ RoofLiner allows for maximum roof coverage and efficient installation—making it easier to install than roofing felt. As a result, there are fewer overlaps, seams and fasteners, which helps reduce both labor and waste.
Superior durability.
In addition to improved water hold-out and better resistance to mold growth, DuPont™ RoofLiner also offers superior tear and UV-resistance when compared to typical roofing felt.
Superior durability combined with higher thermal stability than roofing felt, enables DuPont™ RoofLiner to stand up to the toughest conditions.
* For complete details regarding what roof coverings are identified by ICC-ES AC48, Section 3.0,