Low Pressure Power Washing

High pressure does dammage to wood, gets behind the siding, causes granule loss to roofs, slices through window screens

Those black stains on your roof are a mold called Gleocapsa magma. Another organism that lives on your roof is called lichens.

The answer to this is yes and no.

 One of the functions of including Sodium Hypoclorite, in the wash mix, is to kill the mold and other organisms living on the outside of your home. Once it is dead, the roots let go, and is easily rinsed off!

The down side is if "bleach" isn't handled correctly, or by an inexperienced washer. It can harm plants, flowers, and bushes around your home.

The American College of Occupational and Environmental Medicine states:

"The presence of mold adversely affects human health through three processes: allergy, infection and toxicity." 

---The black and green stains on your roof, siding and wood. Well thats mold.Clogged gutters hold water. Mold likes this also..
To reduce the mold threat, mold should be controlled where it grows, outside. Reducing or eliminating exterior mold reduces the chances of mold getting into your home.  This in turn helps prevent you or your loved ones  from having allergies, or flu like symptoms in the future.

A bonus to the improved curb appeal of the property!

The answer is yes,

Owens Corning feels that because of the contraction and expansion of the algae, it causes granule loss, and shortens roof life.
Bad algae growth can raise the edges of the shingles, and make them more susceptible to being blown off in the wind!
A dirty roof can, and will "infect" the neighbors roof's.
The mold from the roof can wash down onto the paint, driveway, etc, and start growing.

Mold inhibitors are just that. They generally only last a year. Recomended for really bad mold problems.

"wax"? It is a polymer wax added to the wash mix. Just like at the car wash! Adds more lustre to the siding, and also makes a less pourus surface for the mold to adhere to.