How can I prevent algae from forming on my vinyl siding?

Question:My house has vinyl siding, and on the northern, shaded, parts of the house algae forms on the siding and I have to power-wash it a few times a year. Is there any coating or preventative spray that I can put on the siding to stop the algae from forming on there in the first place -- or is it just as easy to power wash?

Answers:
Try using a 50/50 mix of chlorine bleach. Spray it on, leave it for a few minutes and then rinse. The method you've been using doesn't kill the algae spores, that's why it regrowns so quickly. Keep in mind the bleach will kill any shrubs or grass, so you might want to wait until the end of the growing season, or protect them with a tarp.