Most residential roofs have green properties that can fall into two categories: recyclability/use of recycled content, and the roof’s reflectivity/solar emittance rating.
Metal roofs are always made entirely of recyclable material, and other brand-new metal roofs can have 100 percent recycled content. But high-tech EPDM rubber and TPO plastic are now used to create molded, light-weight shake- or slate-like shingles that offer long warranties, impact resistance and UL Class A fire ratings. Many of these new roofing products are made from 100 percent recycled content, and are 100 percent recyclable as well.
But more important is the roof’s ability to reflect (solar reflectance) and emit (thermal emittance) heat from the sun. A roof with black shingles reflects about 5 percent of the sun’s heat. A gray roof, about 20 percent, and white roofs reflect 25 percent. Black roofs get as much as 90 degrees hotter than white roofs. Hotter roofs mean hotter buildings, which are environmentally and financially costly to cool down. EPA figures show that $40 billion is spent each year in the United States to cool buildings. That’s more than 15 percent of all the electricity generated each year, most of which is generated by coal. Imagine reducing that by up to 20 percent with just a change of roof type and color.
Problem is, people dislike white roofs. But now some shingle manufacturers are using lighter-colored shingles and shingle surface treatments that better reflect and emit heat. Granules embedded in the shingles appear dark, yet are highly reflective. Look for an Energy Star label on these roof types. An Energy Star shingle will have, upon installation, a solar reflectance greater than or equal to 0.25, meaning 25 percent of the sun’s heat is reflected. As for metal roofs, they can easily be factory treated with durable, highly reflective coatings and many are Energy Star-rated.
Another label to look for is from The Cool Roof Rating Council. CRRC is the rating system used by California’s Title 24 — the mandated green building standard — but CRRC is not strictly a California program. This group tests roofing material and rates solar reflectance and solar emittance to create a CRRC rating of between 0 and 1. The higher the number, the better. Generally, roofs that are considered cool have ratings in the 0.70 to 0.75 range.