Cleaned the gutters a while ago and the shingle fungus is getting worse: more sites and more stains. I sprized some general-purpose fungicide on the area over the kitchen:
And down the valley between the north and east slopes:
We’ll see what happens by next spring; I hope the larger moss clumps will take the hint.
However, that short length of copper wire seems to be improving things. Here’s the before:
Compared with the current state, from a different spot:
The intense streaks have vanished, leaving a uniform lighter gray layer, and the upper area near the wire looks, mmm, less awful than the lower areas. I think running copper wire or zinc strips (which I have not found at the big box stores) along the ridge vent will do wonders, although I’m not sure how to anchor either one along the hip joints between the other slopes.
The Smell of Molten Projects in the Morning 
Just send the whole thing out for hot-dip galvanizing! :)
I always pondered having a sheet metal shop laser cut a full house size batch of 1:1 size 3-tab stainless steel shingles. Make them thin enough to mount with normal roofing nails. Then just shingle the whole roof with stainless goodness.
In real life, I think they would need to have a texture, to keep water from permanently wicking between them, and of course the expense of stainless steel shingles would be “through the roof” (sorry).
We live in an agriculture area, so it is accepted to use the rolled steel roofing here. If properly installed, that is about as low maintenance and long-life as you can get.
Standing seam metal roofing will last for longer than the lifetime of the average house in the US, and is significantly cheaper than stainless shingles, with the added benefit that it’ll never leak around the roofing nails.
I grew up in a house with rolled-and-crimped metal roofing, which Dad & I covered with aluminum paint every few years. It was a great idea, except during the occasional hail storm: the noise was deafening!
A copper roof would be nice, but pricey…
http://www.rmpolymers.co.uk/previous-projects/keir-hardie-methodist-church-newham-london-copper-roof-wont-get-stolen
Well, because it looks like copper, they’ll still steal the roof. It’s only after they haul the sheets away that they discover it’s more-or-less worthless…
This may be a stupid question but have you considered bleach? It does wonders in removing that stuff and it’s dirt cheap. A small concentration would be safe but still effective. If the shingle material is partially absorbing the effect should even last longer.
Chlorine bleach doesn’t have any permanent effect, so you’re stuck re-applying it fairly often. The stuff also seems to deteriorate asphalt shingles when applied at a useful concentration, although I’m not convinced it’s all that bad.
Much of the breathless hype over “oxygen” bleaches seems, well, overenthusiastic.
Next year I’ll try a few ideas…
People here mix copper suplhate with the paint and I hear that it kills off the fungus. Copper salts kill of fungus I think. We get black streaks on the walls due to 60″ of average rain a year.
Mary uses CuSO4 as a fungicide and the roof is clear below the copper flashing around the chimney, so that will probably work. I think I must install copper strips along both sides of the entire ridgeline, then apply some sort of bleach to the stains. Bleh!