This article originally appeared on the BUILDER website.
In many ways roofing has not changed in the past 10 years, and may not for another 100. But even small changes to the base expectations for a roof’s performance can lead professionals to reconsider the ways they cover new homes.
Since BUILDER’s last in-depth look at the pros and cons of metal and asphalt roofing, energy efficiency has remained a top priority for homeowners looking for lower utility bills and builders planning for HERS scores and certifications. Solar panels have become a common sight on American rooftops, and will be required on all new homes in California by 2020. And many high-profile natural disasters, including California’s wildfires, Superstorm Sandy, and devastating hurricanes on both coasts have sparked a strong focus on resilient and disaster-resistant products.
In light of this, BUILDER has re-examined a simple and widely asked question – will asphalt or metal work best for my projects? How have asphalt and metal roofing manufacturers upgraded their materials to meet today’s standards? Which roofing type will meet my needs for efficiency, or resiliency, or aesthetics? And how will solar panels–or solar roofing –perform against my choice of surface?
With energy efficiency and natural disaster resilience at the forefront of buyers’ minds, both the asphalt and metal roofing industries have taken steps in the past decade to enhance their products’ performance, as well as emphasize existing advantages. Here’s how the two materials have changed – and in some ways stayed the same – since 2010.
Asphalt: Asphalt made up 44% of the steep-slope new construction market and 58% of the reroofing market in 2015, according to the National Roofing Contractors Association, and comprises 75-80% of the total U.S. steep-slope roofing market, according to the Asphalt Roofing Manufacturers Association (ARMA). Over 12.5 billion square feet of asphalt shingles are manufactured annually, enough to cover 5 million new homes every year, and four out of five homes in the U.S. are roofed with asphalt.
Metal: As of 2017, the most recent numbers available, metal roofing sales made up 10% of the overall roofing market, up from 9% in 2010 but down from 12% in 2016. Steep-slope metal roofing makes up 6% of the new construction market, up from 4% in 2016, and 11% of the reroofing market, down from 14% in 2016. Vertical ribbed panels are the most commonly-used metal roofing type with 67% market share by metal type, followed by shingle/shake/tile/slate metal roofing at 24%.
Other: Other types of roofing with much less market share include tile, slate, and shake.
Cost and Lifespan
Asphalt: Asphalt is still one of the least expensive roofing material types at $350-$900 per square. Asphalt has an average lifespan of 15-20 years, according to the MRA, and ARMA notes that roofs over 20 years old are “prime candidates” for replacement.
Metal: Metal roofing, on the other hand, is one of the most expensive, according to the MRA’s material comparisons, at an estimated $800-$1,200 per square for vertical seam and $800-$1,500 per square for stamped panel. Metal roofing has an expected lifespan of 50+ years.
Other: With an expected lifespan of 50+ years, tile roofing ranges from $700-$1000 per square, slate lasts 75 years or more and costs from $800-$1,500, and shake from $800-$1,500, which has a 30-year lifespan with regular maintenance.
Asphalt: The asphalt shingle market has shifted away from traditional three-tab shingles over the last decade to laminated designer shingles, or “architectural shingles.” While these shingles are heavier and more expensive than traditional three-tab roofing, they better emulate the look of other roofing types, including shake and slate.
Across all roofing types, shingles that emulate the look of natural wood shake without the same need for upkeep have grown tremendously popular. “The residential roofing market continues to shift toward laminates,” says Travis VanDaGriff, central district sales manager for TAMKO Building Products. “Laminated asphalt shingles have added dimensionality because of extra layers of fiberglass mat, which create a wood shake-like appearance… Laminated shingle styles are also typically offered with longer warranties and better wind ratings.”
Metal: The metal market has also benefitted from a series of aesthetic advances. A number of manufacturers – including CertainTeed, which introduced metal roofing in 2015 – offer stamped-panel metal shingles in shake, slate, and tile-look profiles. “Metal roofing can look like any other roofing product out there now, both from a shapes perspective as well as a color perspective,” says Renee Ramey, executive director of the Metal Roofing Alliance (MRA). “We’re no longer pigeonholed. We’ve got anything you want, aesthetically.”
Another aesthetic option is stone-coated steel roofing, which combines a metal base with a stone upper layer that can be made to look like tile, slate, or shake. According to Pete Croft, brand manager of steel roofing at Boral Roofing, most stone-coated steel roofing cannot be identified as metal roofing at a glance. This has provided an inroad to metal roofing adoption in areas where homeowners’ associations restrict its use, citing its appearance. “It just doesn’t look like a metal roof,” says Croft. “There’s been numerous situations in California and in other states where presentations have been made to associations, and after they get a true understanding of what the finished roof looks like they change their whole perspective on banning metal roofing from their subdivision.”
Asphalt: Manufacturers have improved the product’s impact resistance with the introduction of SBS-modified or “rubberized” shingles. “Innovative uses of asphalt and fiberglass mat as well as the introduction of polymer modification to some shingle lines have made products lighter in weight while at the same time enhancing their wind and impact resistance characteristics,” says Reed Hitchcock, executive vice president of ARMA. “Maintenance needs vary geographically, but we have seen terrific results from shingles specifically designed with concerns like algae resistance in mind.”
Metal: Following two consecutive years of hurricane destruction and this summer’s devastating wildfires on the west coast, the MRA has increased its efforts to spotlight metal roofing’s resilience.
According to the association, most high-quality metal roofing systems can withstand winds of over 140 miles per hour, the equivalent of an F2 tornado. The roofing carries a Class A fire rating, is “nearly impenetrable” to moisture, and resists impact damage from hail and debris. FEMA recommends its use in fire-prone areas, and Florida’s Monroe County had considered mandates that would have required all new or replacement roofs in the county to be metal following Hurricane Irma.
Material advances in metal roofing include improved coatings and corrosion-resistance. “The substrates have remained the same, but the coatings going over the metal itself have done nothing but improve,” Ramey says. “So from a corrosion perspective, if you’re installing a quality product, then you’re having someone do a quality installation, the corrosion aspect has definitely become less of an issue.”
Energy-Efficiency and Green Certification
Asphalt: One of the largest advancements in asphalt is improvements to shingles’ solar reflectance and thermal emittance, collectively the Solar Reflectance Index (SRI). According to ARMA, while the solar reflectance values of conventional shingles range from 0.04 for black to 0.25 for white, the addition of asphalt granules made with new light-reflecting pigments can raise an asphalt roof’s solar reflective value up to 0.40.
This “Cool Roofing” is designed to reflect solar energy back into the atmosphere, instead of absorbing it into the building and creating strain on its cooling systems. The association also recommends a balanced attic ventilation system and roof or attic insulation to lower the structure’s energy needs.
Metal: Metal roofing's high reflectivity provides up to 30% energy savings over other roofing types, according to the MRA’s material comparisons.
Asphalt: Asphalt shingle recycling programs have grown over the course of the past decade; as of 2017 there are active recycling programs in 50 major U.S. markets. The Northeast Recycling Council estimates that 50 million tons of asphalt shingle scrap is produced through manufacturing and tear-offs each year in the U.S., and that recycling 1 ton of asphalt shingle is the equivalent of saving one barrel of oil. The asphalt and aggregate from these materials has been re-used in road construction and maintenance projects across the country.
Metal: According to the MRA, metal roofing projects are generally made of recycled material, and are 100% recyclable at the ends of their lifespans.
Best Choice for Solar
Asphalt: To install a solar rack on an asphalt roof, installers will usually secure stand-off mounts to the roof trusses with lag screws. “Properly installed, asphalt roofing provides an ideal substrate for solar installations,” says Hitchcock.
According to Hitchcock, there are products currently in testing that integrate asphalt shingles with solar systems, which would provide both protection and sustainable energy. “As these materials continue to develop, this will be an interesting space to watch,” Hitchcock says.
However, as noted by MRA’s Ramey, the usable life of a solar panel (around 25 years) is generally longer than the usable life of an asphalt roof. “If you install a lot of these solar panels over an alternative roofing product, a non-metal roofing product, the roofing product that they’re installed on will not last as long as the panels are warrantied for,” she says. “And what ends up happening is, homeowners have to pull solar panels off to redo their roof, and for a lot of these panels the warranties go void once they’re dismantled and have to be reassembled.”
Metal: By comparison, according to Ramey, metal roofing’s 50+ year lifespan ensures that it will last about as long or longer than the solar panels installed on it. Mounting a solar rack on a metal roof also does not require any roof perforations–installers can affix them to standing-seam metal roofs with non-penetrating seam clamps.
For stone-coated steel, both the MRA and Boral recommend the use of a rail system mount bracket, which also does not require any perforations to the roof, save for one for the solar cable. “On a solar system, when you start mounting holes through the roof to support the legs of the solar system, every hole that you make in that panel tends to be another danger that you’ve got to flash, which could potentially be a problem down the road,” says Croft.