The more active ingredient at preventing rot in the wood preservative CCA ( chromated copper arsenate) is the copper.
“CCA is a mixture of copper, chromium and arsenic - chemical elements that occur naturally throughout the earth’s crust and atmosphere. Copper becomes an effective fungicide when combined with the other elements. Chromium, also toxic to certain fungi, plays an important role in helping the preservatives to chemically bond or “fix” to the wood fibre. Inorganic pentavalent arsenic is used in CCA because of its effectiveness against wood-destroying insects. Unlike the highly toxic trivalent arsenic, pentavalent arsenic is a naturally occurring trace element present in soil, water, air, plants and in the tissues of most living creatures, including humans”
From a roofing site:
[FONT=Arial]Roofing Solutions: Key Danger Signals - What’s Growing On Your Roof?[/FONT][FONT=Arial]gus, and Moss[/FONT]
[FONT=Arial]*Algae, or Gloeocapsa Magma, can spread… from one infested roof to another via the release of airborne spores. As more homes are built closer together, this hardy algae has been able to spread rapidly. *[/FONT]
[FONT=Arial]Algae is well adapted to extreme conditions… heat, long dry spells, UV rays, heavy rain, intense cold, thick snow or high winds doesn’t deter it.[/FONT][FONT=Arial]Fact:
[/FONT][FONT=Arial]The dark color of Algae is a pigmented protective sheath… that encapsulates each cell to protect it from UV rays[/FONT][FONT=Arial]Fact:
[/FONT][FONT=Arial]Copper and Zinc can both inhibit algae growth… Zinc (including pellets) however does have other inherent problems, such as: it’s limited ability to be color matched to roofing shingles, attachment method to roofing shingles, cost and the occasional “bloom” effect due to the build-up of zinc oxide. Copper granules are used instead of zinc for these reasons.[/FONT]
[/FONT][FONT=Arial]*Copper is 10 times more effective against algae than Zinc… Zinc actually becomes less effective against algae quicker than copper *[/FONT][FONT=Arial]Fact:
[/FONT][FONT=Arial]*AR shingles at work…some granules covering the shingle contain Copper encapsulated by a specially developed coating allowing Copper (cupric ions) to be time-released to prevent algae over a long period *[/FONT][FONT=Arial]
[/FONT][FONT=Arial]Dew is the dominant source of water for algae and is the “agent” best suited for the release of the copper in Algae Resistant shingles. Rainwater, although effective, runs off a roof too quickly to provide significant leaching of copper. Dew is also present more days than rain.[/FONT]
[/FONT][FONT=Arial]Algae can go for long periods of time without water… It is unaffected by heat or downpours and is dormant in winter. Algae secretes a material that adheres them firmly to the shingle surface.[/FONT][FONT=Arial]
[/FONT][FONT=Arial]*Algae is killed immediately by copper. FACT: Algae cells are poisoned over time. *[/FONT][FONT=Arial]
[/FONT][FONT=Arial]Algae is a fungus. FACT: Algae, or Gloeocapsa Magma belongs to the Cyanobacteria branch in the Eubacteria family and is not a fungus.[/FONT]
[/FONT][FONT=Arial]Installing a copper ridge or hip shingle with copper granules on an existing roof may overcome an existing colony of algae. FACT: AR granules have not been proven to kill existing algae.[/FONT]
Seems like copper fins may be the item to prevent fungus from establishing and building up on coils,etc. Filtering of air and cleaning is to be expected.