I think most working carpenters are familiar with copper’s ability to discourage fungal growth.  It’s the main additive to pressure treated lumber, imbuing the fast-grown southern pine with the ability to resist wood rot, i.e. fungal attack.  A smaller subset of tradespeople are probably familiar with copper’s use to keep roofs from turning green.  Roofs in damp locations, especially if they’re facing north, tend to develop a covering of algae, lichen, or even moss.  I believe there’s some legitimate difference of opinion about whether the green growths can actually damage the underlying roofing material, but many homeowner’s object to nature’s intrusion on their building.  An old roofer’s trick is to install a course of copper flashing high up on a susceptible roof; rainwater washes…