EPDM roofing has been beefed up over the years by replacing the earlier uncured neoprene flashings with uncured EPDM, the use of tape sealants replacing solvent-based neoprene adhesives, and the innovation of incorporating stronger steel roof decks (80ksi steel for 33ksi), which in turn permitted wind ratings on sheets as wide as 10 feet with fasteners only in the lap areas. While 45-mil (0.045 in) thickness is still used, 60-, 75-, and 90-mil sheets are being used more because of the anticipated heavy traffic on our current roof designs. Generally, these systems may also qualify for longer warranties, i.e. 30 years instead of 20. (It has not yet been confirmed that longer life will be achieved through increased mil thickness, although puncture resistance is certainly enhanced.)
PVC membranes have also been beefed up. Non-reinforced and poorly formulated PVC products have left the roofing market, mainly due to premature shrinkage and embrittlement. As with EPDM, thicker sheets are regularly promoted. Both PVC and TPO are sealed by heat-welding the seams of the sheets. The use of double welds, one on each side of the row of fasteners, has greatly improved wind uplift resistance of the mechanically fastened systems.
Facers on isoboards and gypsum boards continue to get beefed up. Originally faced with paper, gypsum boards used either for underlayment or overlay have evolved into glass facers and or factory-primed surfaces. Isoboards are subjected to a new rolling and crushing test called the rolling load emulator, detailed by NRCA in their report Study of Polyisocyanurate Rigid Foam Board Facer Behavior Using the Rolling Load Emulator. The device simulates the effect of construction traffic that could cause fracturing and delaminating of the interface between foam and facer. Much like gypsum boards, facers on Iso are evolving to glass – and in some cases, very heavily coated glass – which provides the boards with better resistance to moisture, rooftop traffic, hail, etc. The most current development is the introduction of thin, very high density Iso boards as cover boards.
Not to be left out, metal systems are also being beefed up. New heat-resistant underlayments, generally of a non-woven or plastic film and self-adhesive, are used not just at eaves and roof valleys, but instead over the entire roof deck. To meet the cool roof requirements, a number of "cool" pigments were developed. While they look just like the old pigments as seen in visible light, they have higher reflectivity in the infrared range, as detailed at coolmetalroofing.org. Stainless steel-based non-penetrating clamps are used not only for their customary function to hold snow guards in place, but as an efficient means to anchor photoelectric cell panels to metal roofs.
Closed cell sprayed-in-place urethane foam roofing (ccSPF) has also evolved. The Spray Polyurethane Foam Alliance (SPFA) has assisted ASTM in developing ASTM D7425 standards for SPF, including increased compressive strength and density. The SPFA has also implemented certification programs not only for their applicators, but for roofing consultants and material suppliers as well. As mentioned above, the foam urethane business was forced to eliminate blowing agents that affected the ozone layer. While pentane is okay under factory conditions, the danger of static electricity requires a non-flammable blowing agent for field application. A new blowing agent called Enovate (HFC245fa) meets that need.
A scorecard for where the beef is:
||4-5 ply organic felt, surfaced with asphalt flood coat and aggregate
||3-ply glass fiber, cap sheet, hybrid wtih MB cap over multilayer BUR
||European technology; SBS usually mopped, APP technology usually torched
||Solvent-based cold adhesives, self-adhering membranes, reflective coatings over granule surfacing
||Uncured neoprene flashings, multi-step lap sealing, narrow sheets, 45 mil thickness, neoprene adhesives
||Fasten only in laps using 80 ksi steel decks replacing 33 ksi, 10-foot-wide sheets, butyl tape replacing wet lap adhesives, Increased mil thickness
||32-48 mil, non-reinforced, single weld seams
||40-90 mils (some KEE producers still market thinner sheets), reinforced, double welds, reflective, recyclable
||ASTM Standard D6878 finally published
||Wide sheets, reflective color, low cost
||Glavalume and Kynar finishes
||Non-penetrating clamps for snow guard and PV frame supports, cool pigments, innovative underlayments
||Minimum density established, chlorofluorocarbon (CFC) blowing agents (Freon 11)
||Accredited suppliers, contractors and consultants; HFC245fa blowing agent
||Paper-faced gypsum boards
||Glass-faced primed gypsum, high-density Invinsa-faced high density isoboards, retrofit boards, tapered insulation
Tips for Selecting Rigid Roof Insulation
The best roof insulation choice meets thermal needs, energy codes, and performance requirements, resulting in a roof system that performs well over the long term.
Thermoplastic (Heat-Weldable) Roofing
Learn about weldable single-ply systems, including thermoplastic polyolefin (TPO), polyvinyl chloride (PVC), ketone ethylene ester (KEE), chlorinated polyethylene (CPE), chlorosulfonated polyethylene (Hypalon or CSPE), and polyisobutylene (PIB) .
For the last year, attention seems to be more on cool roofing, LEED, and vegetated roofs rather than what the roofing system is made of or what it can do. Maybe because current roofing systems are all well established, so they're no longer newsworthy? Several claims are being made as to which manufacturer has lowest carbon footprint and which products are truly recyclable.