I thought I would add my $.02 of advice regarding Terra Wash. 

Terra Wash is a great choice for treating/cleaning residential surfaces like vinyl and aluminum siding, stucco, EIFS, concrete sidewalks, wood and composite decks and fences, and many other surfaces, including cedar siding and cedar roofs.  The soap, or degreaser, in Terra Wash is a safer, but higher priced, chemical than the soap in many other degreasers and general purpose soaps available at your supplier.

These other products typically contain sodium hydroxide, NaOH, a more caustic, potentially damaging compound.  When our primary service was pressure washing, including sidewalk cleanup and parking garage cleaning, a strong, sodium hydroxide degreaser was our best friend!  How many houses need grease, oil or tar removed from them?  It must be stored in plastic containers because it will etch and dissolve glass.  It is also the degreaser in most retail wood strippers, used to remove oil based wood sealers.  It is more powerful for removing the black staining/oxidation damage from gutters and downspouts, but is far more likely to also remove the paint.  The most extreme case I experienced was COMPLETLEY removing the white paint from an older gutter so that about 16' of gutter had ABSOLUTELY NO WHITE PAINT REMAINING ON IT!!!  All of the anodized painted surfaces on any building are prone to paint damage from NaOH as well.  You do not need to remove the paint in order to have visible paint damage.  And it will not do you the favor of being consistent so that the new paint color is uniform.  Further, NaOH left on windows on a hot day, or sprayed directly onto a hot window, can etch the glass, causing irreparable damage.  The only solution at that point is to replace the glass.

Sodium Hydroxide is a stronger, cheaper soap.  However, when weighed against the potential damage, and training necessary to properly use it, I have chosen to no longer use our sodium hydroxide soap.  We began using Terra Wash last year, along with our sodium hydroxide soap, but have since stopped buying it.  We now use only Terra Wash.

BTW--we have also used other products, like D-limonene (orange cleaner).  A very robust degreaser, but it is also a water-based paint stripper.  When I sold bulk industrial chemicals, one of my clients used it to remove dried asphalt from their paving equipment.  If you are using an orange cleaner, you are playing with fire!  And yes, D-limonene is flammable.