Prolonging Roof Life
Weathering of roofing materials includes UV degradation, the high energy ultraviolet rays that attack chemical double bonds and result in embrittlement. For bituminous roofs, including asphalt and coal tar pitch (both considered BUR) and polymer modified bituminous systems, UV protection is provided by surfacing with roof aggregate or roofing granules because they are opaque to UV light.
For smooth-surfaced bituminous systems, solvent-based asphalt-aluminum and fibrated asphalt-aluminum roof coatings were once popular, with the flakes of aluminum pigment providing the UV screen.
Water-based acrylic coatings can be applied to weathered asphalt surfaces, and a number of low-VOC products are offered as well. At least one modified bituminous manufacturer applies a white coating to granulated sheets during production, which adds UV screening and a more reflective surface than is possible with granulated sheets only.
For single-ply systems, UV is screened by reinforcing the polymer with fine carbon black particles (such as black EPDM) or titanium dioxide pigment in light-colored EPDM, PVC, or TPO membranes.
Chemicals that help absorb ozone also prolong roof life. One single-ply manufacturer has just added factory-applied liquid Kynar, a fluoropolymer coating that has long been the coating of choice for standing seam metal roof panels. Several acrylic coatings are now available to surface many types of membranes. The newer acrylic materials are more elastic and have better adhesion to properly prepared substrates than the first generation materials.
Protecting Roof Warranties
The typical length of roof warranties has grown to 30 years or more. Perhaps this was done since the projected life of rooftop solar panels is 30 years or more and it’s extremely difficult to access the roof membrane under solar panels. Most membrane manufacturers strongly recommend against installing panels on aged roofs to avoid the huge expense of removing and replacing the solar panels when the old roof must be replaced.
Typical warranty requirements/recommendations include:
- Upgrade the roof membranes. For BUR, this might be to install 4-ply membranes instead of 3-ply. For MB systems, the use of thicker base and cap sheets may be appropriate. Single-ply may require 90-mil (0.090-inch) membranes instead of thinner ones. Sprayed-in-place polyurethane foam with a density of 2.3 psf or greater offers higher compressive strength.
- Upgrade the thermal insulation to greater than R-20, depending on the climate.
- Face the thermal insulation by using a coverboard such as gypsum to increase the indention and impact resistance from traffic and hail.
- Manufacturers recommend that warranted roofs be inspected twice a year, when the ducks fly north and when they fly south. Then, whenever the membrane is exposed to severe storms or when new equipment is installed on the roof, conduct a special inspection. All manufacturers warn that abuse is excluded from the warranty and strongly recommend that repairs should be completed by certified contractors, either the original roof installer or another who is approved to make repairs.