+1 for adding in the cost to support the extra weight. Many homes, even ones they're building now, are not designed to support anything more than a few layers

+1 for adding in the cost to support the extra weight. Many homes, even ones they're building now, are not designed to support anything more than a few layers of standard asphalt shingles. BTW, it's ridiculous that we're talking "down" to asphalt shingles now because of this. Some of those come with 50+-year warranties now...