Days ago, Jerry stopped by my website, AsktheBuilder.com. He reads my column each week in his local paper and was perplexed by algae growth on the exterior of his home. Jerry hales from Chesterton, Indiana, the gateway to the massive sand dunes at the south end of Lake Michigan.
Here’s what he wrote: “My vinyl-sided home has a northern exposure that gets an algae-like film on it. It gets dark enough that I have to power wash it every year. What’s really confusing is that the south side of the house, the sunny side, doesn’t have this problem. With one-foot eaves, the north side never gets any sun. The south side gets diffused sun shade by honey locust trees. Do you have any idea what causes this?”
