PORTLAND, Ore.—Nearly 14 percent of U.S. homeowners now have metal roofs, which experts say is an especially good choice in the winter months thanks to the exceptional energy efficiency, low maintenance benefits and ability to hold up under heavy snow and ice that metal roofs offer. However, according to the Metal Roofing Alliance (MRA), that’s not to say that metal roofs don’t need a little TLC this time of year.…