Tom Eagar's copper roof (personal)

$9,000 for ~50 sq ft of copper roofing on Tom's house, justified as a 100–300 year lifetime. Lateral example of when copper's price is worth paying.

So we use copper for electrical conductivity, we use it for non-sparking tools, we use it for corrosion resistance in piping — underground piping. I spent nine thousand dollars to put about 50 square feet of copper on my roof, because hey, it'll be there a hundred years from now, it'll be there 300 years from now. If my house is there I won't be, but anyway. Copper alloys in many cases have excellent electrical properties, excellent corrosion-resistant properties, but we're only going to pay that price when we need those properties. As structural materials — other than piping for corrosion resistance when you're burying it in the ground — we usually have other things we can use that are a lot cheaper. That's the competition between materials. Other questions?