http://roof-cleaning-institute.activeboard.com/forum.spark?aBID=123190&p=3&topicID=41055740&page=1

Florida-Roof Cleaning by Chuck Bergman

941-698-1959

Chuck Bergman Soft Wash Roof Cleaning has been serving Charlotte and Sarasota Counties in Florida since 1991 { Prior to that as Chuck Bergman Pressure Cleaning-since 1989 }

With years of experience , it became clear to me that while pressure washing roofs made them look clean, damage was occurring on the roofs. Pressure cleaning machines can only be turned down so far and still accomplish roof cleaning and any amount of pressure, even as low a setting as 500 psi { 3000 to 4000 is what most pressure cleaning contractors use } will still remove around 15-20% of the granules that make up the color and protection of your shingle roof per cleaning.

Ugly black algae, left in place on the roof, eats around those granules and the rain removes them. Still eventually destroying the roof and spoiling it's appearance and resale value. With tile roofs, pressure removes the glazing many tile roofs come with. Pressure also blows pieces of cement that hold the ridge-caps in place off into space! If your tile roof is painted, pressure will blow portions of paint off all over the roof, leaving it in need of an expensive paint job!

So, what to do?

In 1991 I started developing a system to clean roofs without using pressure.

I actually thought I was inventing the method. Later that year, I found out I was wrong and that a few already were doing what we now call Soft-Washing.

Now these roof cleaning systems are available for purchase commercially.
In the attached link, you can read how the this Roofing Manufacturers Association says to clean roofs. That is the only method I use. So your warranty will not be voided.

http://www.asphaltroofing.org/pdf/tb_217.pdf 

From GAF Roofing Manufacturers about black algae removal:

http://www.gaf.com/Documents/Algae_Staining_on_Shingled_Roof_Surfaces_-_Steep_Slope_Techn-43-808-v3.pdf

THIS IS GAF'S NEWEST BULLITEN- http://www.gaf.com/Documents/TAB-R-2011-102_Algae_Staining_On_Shingled_Roof_Surfaces_-_St-438-808-v7.pdf"

If a new roof is not an option, GAF recommends cleaning the roof with a special mixture. That mixture is:"
'bleach and TSP'

"What NOT To Do! Do not power wash the shingles to clean the shingles. Some roof cleaning companies offer this service.
However, it is not recommended."


From ARMA roofing manufacturers Association-how to clean roofing.

http://www.asphaltroofing.org/pdf/tb_217.pdf

"Algae discolorations to remove from roofing surfaces, applying a solution of
chlorine bleach, trisodium phosphate, and water. Solutions for these ingredients depend on the amount of discoloration. Solutions range to one cup TSP and 2.5 gallons each of bleach and water. 
Caution!
High pressure washing systems for algae removal should not be used."

From Owens Corning Roofing Manufacturers :

"USE CHLORINE and TSP" "DO NOT USE A PRESSURE WASHER"

http://webapps.easy2.com/cm2/flash/generic_index.asp?page_id=36077811

This one from the ARMA says not to allow anyone to apply any *after coating* such as Algaecides, Fungicides, Copper, Zinc, or other Roof treatments - not anything!

http://www.asphaltroofing.org/pdf/tb_227.pdf