Industry expert Tony Chiovare, president, Custom-Bilt Metals, discusses the state of ventilation for metal roofing:

For steep slopes, are today's ventilation requirements the same for metal as for asphalt shingles?

With the development of cool roofing, metal roofs may not need ventilation to the same extent as is often necessary with asphalt composite shingles, according to Custom-Bilt Metals President Tony Chiovare. (Photograph courtesy of Custom-Bilt Metals)

Chiovare: Ventilation can serve two purposes: First, it reduces heat build-up within an attic space and, therefore, reduces cooling costs during the summer months. Second, it reduces the amount of warm, moist air that, when it touches a cold surface, may cause condensation within the attic space. With the development of cool roofing, which reduces heat build-up, it may be possible to decrease the amount of ventilation necessary for asphalt composite shingles — and get the same results. Further research is needed. On a low-slope roof, with an air space between the metal and underlayment, we assume a nonpermeable underlayment is usually required. I'm not aware of any jurisdiction where a nonpermeable underlayment is specifically required, but the best roofers will include such an underlayment, even if it's not required. If the roofer offers a nonleaking warranty, he'll insist on a nonpermeable underlayment, such as an ice and water shield, in addition to roof decking. So a nonpermeable underlayment is a very good idea, because it doesn't increase the cost significantly; it's certainly a justifiable addition to a roofing project performed by a quality roofer.

Metal detractors say that, while the shingle will last as advertised, the coating may not, and the product will discolor long before then. How would you respond?

Chiovare

Chiovare: This may have been an issue before Kynar became the standard in 1990, but today it's no longer a significant factor. Kynar coatings have a 25-year warranty. Kynar with cool roof pigments offers a 35-year warranty because its surface is cooler; therefore, there is less expansion and contraction.

We've also heard comments — but no data — that metal can "hold in" the heat from an internal fire and create a greater hazard. Any merit to this, as well as the possibility that the fire chief's associations are supposedly looking into this?

Chiovare: This "barrier" idea comes from the past, when metal was a less common roofing material. Twenty years ago many first responders were not trained and prepared with the proper tools to cut through the metal while fighting a fire. For years many fire departments ventilated roofs by cutting holes in them with axes. Fire departments came across a stumbling spot in the early 1990s, when metal roofs became popular for residential homes. Since then, fire departments have held many training sessions for their personnel to use portable saws when a metal roof is encountered. Today's modern fire departments are equipped to effectively fight a fire in a building with a metal roof. In addition, because they're noncombustible, metal roofs can actually help to prevent fires started by lightning, or sparks or burning tree branches that could fall on them in a wilderness fire scenario. And today's fire insurance premiums are typically lower for homes with metal roofs.